Water Management Plan   for Ashfordton [WLOs: 1, 3] [CLOs: 2, 4]
Prior to beginning work on this discussion forum, review Chapter 5 in the course textbook.
Imagine that you are a resident of Ashfordton, a community whose characteristics are described below. You have come together with your neighbors for a special meeting to devise a plan for managing its water resources more sustainably by 2050. Water resource issues the community faces include insuring a safe and sustainable drinking water supply for all, handling its wastewater in a manner that has minimal environmental impact, and managing its stormwater runoff in a way that minimizes the risks of erosion and flooding.
Fortunately, you have all attended the meeting with the knowledge that you have gained from your readings in this course. Now it is time to put your thinking cap on and get to work! Your ideas should each consist of one of the following elements, depending upon what you think is Ashfordton’s area of greatest need:
· Sustainable drinking water access measures (e.g., developing a program for rural residents to begin collecting and treating their rainwater for drinking use).
· Sustainable wastewater management measures (e.g., collecting greywater from area residences for use irrigating a local golf course).
· Storm water management measures (e.g., requiring that permeable pavement be used for all future development projects in the community).
This week’s discussion will take place in an online app called Tricider. There, you will be able to post your ideas for plan components and also share pros and cons of different proposals during the week. Finally, you will be able to vote on the three components that you think the plan should include. For directions on how to use the Tricider app, please review the Tricider Help Guide. In Tricider. You will be expected to do the following:
· Post at least two separate and entirely original ideas. Do not duplicate ideas already posted by your peers.
o Include your full name for each one.
· Post at least six different pros and six different cons for your classmates’ proposed ideas (12 in all).
· Vote on what you feel are the top three ideas in the list.
o Do not vote before Friday, so that you can vote from the full collection of student ideas.
You must complete the three tasks above to receive full credit for this discussion.
Water Management Plan   Voting Rationales [WLO: 1] [CLOs: 3, 4, 6]
Prior to beginning work on this discussion forum, read Chapters 5 and 6 in your course textbook.
Now that you have cast your votes for the Ashfordton Water Management Plan, it is time to explain your choices to the class. Please make a post of at least 150 words in which you
· Identify (briefly) the plan elements on which you voted.
· Explain why you selected each one.
Each of the elements with an explanation is worth .5 point for a total of 1.5 points.
Note: You will not be able to view others’ posts until you have made your own. At the end of the week, the instructor will post the winning Ashfordton Water Management Plan, which will include the top three ideas selected by the class. In cases where two action items are judged by the instructor to be nearly identical, the instructor reserves the right to combine the ideas into a single one (and add votes together) in order to determine the winning ideas. This plan will be posted in the Announcements area of the classroom.

5 Sustaining Our Freshwater Resources

borgogniels/iStock /Getty Images Plus

Learning Outcomes

After reading this chapter, you should be able to

• Describe how New York City worked with nature to improve its water supply.
• Illustrate the water cycle and how the planet’s water is distributed.
• Define different types of water use.
• Analyze the methods used to meet global water demand.
• Describe the potential for global conflict over water.
• Describe different types of water pollution and ways to manage that pollution.
• Differentiate between the hard path and soft path approaches to water management.
• Discuss the role of forests in water management.

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Section 5.1 Case Study: New York City’s Water Supply

When viewed from space, Earth is a watery planet, with oceans covering over 70% of the
planet’s surface and glaciers, ice caps, lakes, rivers, and streams covering another 10%. Yet
water shortages and access to clean, safe drinking water are a serious problem in virtually
every region of the world. The abundance of ocean water is too salty for human use, and much
of the freshwater is either polluted or inaccessible.

Given its importance and critical role in all human life, it is remarkable how poorly managed
water is as a resource. We regularly use rivers, streams, and the oceans as a dumping ground
for our wastes and allow contaminants like spilled oil and agricultural chemicals to pollute
critical groundwater supplies. We dam rivers and use massive amounts of energy to pump
water hundreds of miles to irrigate golf courses and suburban lawns in the middle of deserts.
And we pay little attention to how the management—or mismanagement—of natural capital
resources like forests, wetlands, and other open spaces impacts water quality in surrounding

This chapter will examine issues of freshwater management and consider the challenges of
both water quantity and water quality. The next chapter will examine issues and challenges
associated with our oceans.

We will first discuss issues of water quantity, which involve ensuring that there are adequate
supplies and that mismanagement of water does not result in flooding. Only a tiny fraction
of water on the planet is accessible and suitable for human consumption, making wise water
management a critical priority. We’ll also see that just as with other critical resources like
food and energy, water use varies greatly in different regions of the world. We will then con-
sider issues of water quality, which involve ensuring that water is safe to use. Lastly, we will
look at ideas and approaches for water conservation and sustainable water management,
including efforts both to increase the availability of water on the supply side and to reduce
usage on the demand side.

5.1 Case Study: New York City’s Water Supply

New York City has long prided itself on the quality of its municipal drinking water, with some
residents and city boosters going so far as to call it the “champagne of tap water.” Over the
years the city has garnered awards for the quality of its water relative to other major cities
in the United States, and chefs and food experts have debated whether the city’s water might
have something to do with the quality of its pizza and bagels. A Southern California–based
pizza business even goes so far as to spend $10,000 a year to have New York City tap water
trucked across the country to use in making dough for its New York–style pizza.

The story of why New York City’s water quality is so good and how the city addressed contam-
ination can help us begin to understand the issues discussed in this chapter and the impor-
tance of sustaining freshwater resources.

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Section 5.1 Case Study: New York City’s Water Supply

Building a Water Supply System
As far back as the 1830s, city leaders in New York knew that, in order for the city to grow and
thrive, they needed to do something about their water supply situation. At the time, the city
drew its water from a patchwork of ponds, springs, and underground wells, but overuse and
poor waste management were affecting both the quantity and the quality of the city’s water
supply. Massive fires burned through wood-framed buildings because water pressure was
too low to fill fire hoses. Overpumping of wells led freshwater levels to fall below sea level,
allowing the nearby ocean to seep in and contaminate groundwater supplies. The raw sew-
age and animal waste being dumped in the streets ran off and contaminated ponds and small

After a cholera epidemic (due in large part to poor water quality) killed thousands in 1832
and the Great Fire of New York burned 17 city blocks in 1835, city leaders embarked on a
massive water development project that would change the course of New York City history.
A dam was built on the Croton River north of the city, and a 65-kilometer (40-mile) covered
aqueduct was built to carry water from there to the middle of Manhattan, where Central Park
is located today. When the new water supply system opened in 1842, it carried 340 million
liters (90 million gallons) of clean water every day to the thirsty city.

Sixty years later, the system was expanded
on as city officials sought to prevent water
shortages and inadequate supply while
New York City grew and expanded. Water
development projects were undertaken fur-
ther north and west of the city in the Catskill
Mountain region. An entire series of dams,
reservoirs, aqueducts, and tunnels were
constructed in the early 1900s, and by 1915
the Catskill Aqueduct was in operation.

Today New York City’s water supply system
is still based almost entirely on the projects
from the 1800s and early 1900s. Each day
over 4.5 billion liters (1.2 billion gallons)
of water are delivered to New York City’s
9 million residents, with 10% of this water
coming from the Croton portion of the system and 90% originating from the Catskill portion.
The Catskill watershed region, over 160 kilometers (100 miles) away from the city, draws
water from 19 reservoirs and 3 lakes spread out over a 500,000-hectare (2,000-square-mile)
area. A watershed is an area of land where sources of water (streams, creeks) flow together
to a single destination. These lakes and reservoirs are connected to the city by 10,000 kilome-
ters (over 6,200 miles) of pipes, tunnels, and aqueducts. Because of differences in elevation,
almost the entire system moves water through gravity, with a drop of water taking anywhere
from 3 months to 1 year to travel from an upstate lake or reservoir to a customer in the city. As
the water approaches the city, it’s treated with chlorine to kill germs and pathogens, as well
as fluoride for dental health and a couple of other chemicals to prevent corrosion of pipes.

Elizabeth Petrozello/iStock /Getty Images Plus
The Ashokan Reservoir in the Catskill
Mountains is one of several to provide New
York City with its water supply.

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Section 5.1 Case Study: New York City’s Water Supply

Unlike most major urban water systems, New York City’s drinking water is not filtered. In fact,
New York has the largest unfiltered drinking water system in the United States. New York’s
water supply reservoirs were built in upstate areas that were covered in forests and that
also had vast areas of intact wetlands. These forests and wetlands act as natural sponges and
filters, absorbing rainfall and snowmelt and purifying the water in the process. Many other
cities that draw their drinking water from nearby lakes and rivers need to have expensive fil-
tration systems to remove sediment and other particles and contaminants before distributing
water to residents.

Learn More: New York City’s Water Supply

To get a sense of how vast the Catskill watershed region is, visit the following link:


Expanding Ecosystem Management
By the 1990s, however, things began to change for the worse in terms of New York City’s
drinking water. Increased development, road building, suburban sprawl, and other activities
in the Catskill region were having a negative impact on water quality in surrounding reser-
voirs and lakes. U.S. Environmental Protection Agency (EPA) inspectors warned the city that
it might have to build a $10 billion water filtration plant to address the issue.

Instead, New York City decided to take a different approach. The 1997 Watershed Memoran-
dum of Agreement (MOA) was negotiated between New York City, New York State, the EPA,
environmental groups, and municipalities and townships in the Catskills region. The MOA
committed New York City to spend just under $2 billion on a range of initiatives intended to
improve water quality in the Catskill reservoirs. These initiatives included purchasing and
protecting lands surrounding reservoirs and lakes, as well as paying nearby landowners who
agreed not to develop their lands commercially. In addition, the city helped upstate communi-
ties improve wastewater treatment plants, assisted dairy farmers with manure management,
and worked with road departments to ensure that runoff from roads and highways was not
entering reservoirs. Lastly, the city provided funding for upstate home owners to upgrade sep-
tic systems and for forest landowners to improve forest management practices. Collectively,
these approaches are known as ecosystem management because they focus on maintaining
water quality at the source rather than cleaning the water as it reaches its destination. Over
the past 20 years, the ecosystem management initiatives undertaken as part of the MOA have
proved effective enough that the EPA has granted New York City a series of “filtration avoid-
ance determinations” that allow the city to operate its water system without a filtration plant.

The ecosystem management approach has been supplemented with high-tech features,
including a network of hundreds of robotic buoys deployed across reservoirs to continually
test and monitor water quality. These robotic water quality monitors test over 1.9 million
water samples each year. In addition, the city has recently put in place the world’s largest
ultraviolet water disinfection facility. Water passes through containers mounted with ultra-
violet lights that kill any microorganisms that might contaminate the water and make con-
sumers sick.

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Section 5.2 Freshwater Systems

While New York City water officials must always be vigilant in ensuring the quality of the
city’s water, the success of the MOA initiatives points to the importance of “source manage-
ment” as an approach to meeting our water needs. Rather than spend $10 billion building
a water filtration plant to treat polluted water at the back end of the system, New York City
spent one fifth of that amount to ensure that its drinking water was not polluted at the source
in the first place. Essentially, New York City has been investing in the natural capital resources
of forests and wetlands in the Catskills region and letting this natural infrastructure provide
the ecosystem service of keeping the city’s water clean.

5.2 Freshwater Systems

Water is perhaps the most critical resource to human well-being and survival. Our bodies are
made up of as much as 60% water, and while healthy individuals can survive weeks without
food, they would last only a few days without water. We also rely on water to grow food,
produce energy, and manufacture just about everything imaginable. In addition, we depend
on and benefit from a range of ecosystem functions and services provided by water, includ-
ing transportation, recreational activities, and wildlife habitat. We regularly rely on rivers,
streams, and oceans to dilute and purify our waste products, although this use frequently
conflicts with the other ecosystem functions and services that water provides. Despite all the
ways we depend on water, we seldom give much thought to where it comes from and how it
gets to us.

Water Distribution
It’s been said that we live on a “blue planet,” since water covers nearly three fourths of the
Earth’s surface. However, when we account for where water is located and what condition it
is in, we realize that water is not only a critical natural capital resource but also a scarce one.
How can it be that such an abundant resource can also be scarce at the same time?

Imagine the world’s water as 1 million individual 1-gallon containers. (In reality, there are
370 million trillion gallons.) For starters, about 970,000 (97%) of those containers would
be filled with salty ocean water unsuitable for human consumption. It was this reality that
inspired the line from The Rime of the Ancient Mariner, “water water everywhere, nor any drop
to drink” (Coleridge, 1919/1990, lines 121–122). Another 26,100 gallons (2.61%) would be
filled with ice and snow—nearly all of it from ice caps and glaciers in the Arctic and Antarctic
regions, far from major human populations. Roughly 3,600 gallons (0.36%) would be filled
with groundwater, with much of this (but not all, as we will learn) consisting of salt water also
unsuitable for human consumption.

Out of the 1 million gallons we started with, only 300 gallons remain. Some of those 300 gal-
lons consist of water vapor in the atmosphere, water found in saline or salty lakes, or water
in the soil, leaving just about 180 gallons (0.018%) of fresh surface water—water on the
surface of the Earth, found in rivers, wetlands, lakes, and reservoirs. Because this fresh sur-
face water is the primary source of water for most people on the planet, we can see just how
scarce and precious this resource actually is. (See Figure 5.1.)

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Section 5.2 Freshwater Systems

Thankfully, nature has a way of constantly recycling, replenishing, and purifying water sources.
In fact, unlike other resources (such as fossil fuels) that are permanently “consumed,” global
water supply is more or less fixed. This is because of the global hydrologic cycle. The hydro-
logic cycle, or water cycle, describes the movement of water between the planet’s surface,
atmosphere, soil, oceans, and living organisms. If we think again of our 1 million gallon con-
tainers, the water cycle is constantly moving water among the different containers, although
human activities are increasingly interfering with this process and further complicating effec-
tive water management.

Water Cycle
The global water cycle is driven primarily by solar energy. Heat from the sun causes water to
evaporate from surface waters and land surfaces and enter the atmosphere as water vapor.
For example, it’s estimated that solar energy evaporates roughly 425,000 cubic kilometers
(km3) of ocean water each year. To put that in perspective, just 1 cubic kilometer of water is

Figure 5.1: Water distribution

Only 0.6% of the world’s freshwater—0.018% of all water on Earth—is readily available as surface water
for human use.

Source: Data adapted from “Where Is Earth’s Water?” by US Geological Survey, n.d. (https://www.usgs.gov/media/images/distribution

Earth’s water



Fresh surface
water (liquid)


Ice caps
and glaciers





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Section 5.2 Freshwater Systems

equivalent to a tank of water that is 1,000 meters (3,280 feet) tall, wide, and long, or 1 tril-
lion liters (265 billion gallons). The amount of energy it takes to move this much water from
the ocean to the atmosphere is massive. Roughly one third of all the solar energy striking the
Earth each day is used to drive evaporation.

In addition to evaporation, plants draw massive amounts of water from the soil and release
some of that water to the atmosphere as water vapor through a process known as transpira-
tion. Evaporation and transpiration are together known as evapotranspiration. As water
vapor from evapotranspiration rises into the atmosphere, it cools and condenses to form
clouds (condensation) before falling back to Earth as rain and snow (precipitation). Evapo-
ration, transpiration, condensation, and precipitation form the basis of the water cycle (see
Figure 5.2).

Figure 5.2: The water cycle

The basis of the hydrologic cycle is condensation, precipitation, and evapotranspiration. Once water
reaches the ground, it either runs off into nearby bodies of water or infiltrates the surface, where it
reaches the water table and underground aquifers.

Source: Based on “Ground Water and Surface Water a Single Resource,” by US Geological Survey, 2013 (https://pubs.usgs.gov/circ

Groundwater flow

Surface runoff


r flow




Water table











The processes of evaporation and condensation purify water naturally because only water
molecules are pulled into the atmosphere, leaving any salts, contaminants, or pollutants
behind. This is basically the same as making distilled water by boiling water and condensing
the vapor. Roughly 90% of the ocean water evaporated each year falls back as precipitation
over the oceans, where it mixes again with salt water. However, about 10% of that moisture
falls over land surfaces as freshwater precipitation.

An even larger amount of freshwater precipitation is provided by evapotranspiration from
plants and forests. In tropical forests as much as 80% of all precipitation comes from the
direct recycling of evapotranspiration from plants. This feedback loop—more trees leading to
more transpiration leading to more precipitation leading to more trees—is a key reason why
forest management is so tightly linked with water management.

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Section 5.2 Freshwater Systems

Overall, of the 110,000 km3 of precipitation that falls over land surfaces each year, it’s esti-
mated that roughly one third comes from moisture drawn from ocean waters and two thirds
from moisture from evapotranspiration from plants. This 110,000 km3 of precipitation ends
up doing one of three things. First, about two thirds of that water evaporates back into the
atmosphere from land surfaces or through plant transpiration. The other one third either
flows over land and enters rivers, streams, and lakes (surface water) or gradually percolates
through soil and rock to enter underground aquifers (groundwater). It’s this relatively small
amount of water, roughly 37,500 km3 per year, that replenishes the tiny sliver of fresh surface
water illustrated in Figure 5.1 and represents the total renewable supply of fresh surface
water on the planet. As with most other resources, this freshwater supply is unevenly dis-
tributed around the world. Atmospheric circulation patterns, topography, and proximity to
water sources and forests are all factors that influence the amount of precipitation in a given

Human Impact on the Water Cycle
Human activities can also affect precipitation patterns and what happens to that precipitation
after it falls to Earth. Under normal conditions, as precipitation reaches the ground, some of
it is pulled below the surface by gravity through a process known as infiltration. This water
eventually reaches the water table, a depth below ground where soil and rock are completely
saturated with water. The saturated area immediately below the water table is known as an
aquifer, an area of permeable rock and sediment from which water can be extracted.

Many communities, private home owners, factories, and farmers use pumps to pull ground-
water from aquifers to the surface. As long as rates of infiltration are the same or greater than
rates of extraction, the water level in the aquifer will be maintained. However, this is often not
the case, and overpumping is resulting in aquifer depletion in many locations, such as with
the Ogallala Aquifer in the U.S. Midwest (recall Chapter 4). As New York City discovered in
the 1830s, overpumping of water from aquifers near the ocean can also cause the problem
of saltwater intrusion as lower freshwater levels in the aquifer allow adjacent salt water
to enter and contaminate that supply. Saltwater intrusion is a worsening problem in coastal
regions around the world today.

Land use on the surface also affects how
quickly aquifers can recharge. Developed
areas like cities and suburbs have replaced
grassland and forest soils with a lot of imper-
meable surface area. Most roads, driveways,
parking lots, and roofs of buildings do not
allow rain and melting snow to infiltrate
into the ground and instead increase run-
off. This increased runoff can result in more
floods as too much water moves too fast
across the surface and is not absorbed into
the ground. Recent research demonstrates
how too much impermeable surface area
greatly worsened the impacts of Hurricane
Harvey in Houston in 2017 (Zhang, Villarini,

Cameron Whitman/iStock/Thinkstock
Heavily developed and paved areas create
a problem for our water supply, since rain
and snow cannot easily penetrate back into
the Earth.

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Section 5.3 Global Water Use and Demand

Vecchi, & Smith, 2018). More and more cities, municipalities, developers, and home owners
are beginning to consider ways to cut down on water runoff and increase rates of infiltration
in order to increase and improve groundwater supplies as well as prevent flooding.

The water cycle makes available the freshwater that all human life relies on, constantly recy-
cling and replenishing this scarce resource. Unfortunately, human activities such as over-
pumping of groundwater and paving of surface areas are negatively impacting both the quan-
tity and quality of our water supply. This is happening at the same time that global water
use and demand is increasing with population growth. The next section takes a closer look
at global water use and how that demand can be met, given the finite supply of freshwater
available to us.

5.3 Global Water Use and Demand

Recall that an estimated 110,000 km3 of precipitation falls over land surfaces each year and
that 37,500 km3 of this enters surface waters or percolates into underground aquifers. This
37,500 km3 represents the theoretical supply of renewable freshwater on the planet each
year. If all this water were available to us, it would be more than enough to meet human needs.
However, a few factors complicate this picture.

First, where this precipitation falls does not
always align with where humans reside.
For example, large amounts of precipita-
tion fall to the ground and flow to the sea
in sparsely populated regions of the Ama-
zon basin in South America or in remote
areas of central Africa. Second, when this
precipitation falls can make water manage-
ment challenging even in very wet places.
For example, in tropical regions of Asia that
experience heavy rainfall, as much as 80%
to 90% of annual precipitation can fall dur-
ing just a few months of the monsoon, with
relatively dry conditions prevailing for the
other months of the year.

As a result, and despite adequate supplies of water on average globally, we face water short-
ages and scarcity in many regions. Over 2 billion people lack access to adequate and safe water
supplies, and over 4 billion lack access to proper sanitation (World Water Assessment Pro-
gramme, 2019). As a result, at least 2 million preventable deaths occur each year from water-
related diseases that mostly claim the lives of young children (WHO, n.d.b). In some cases,
problems arise from an absolute scarcity of water, whereas in others there is inadequate infra-
structure to meet a population’s water requirements. This section will consider those issues of
water quantity: its use and demand and how human water needs are being met.

Antoninapotapenko/iStock /Getty Images Plus
Tropical regions such as Asia can get 80% to
90% of their total annual rainfall in as little as
3 months due to natural weather conditions.

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Section 5.3 Global Water Use and Demand

Let us return to the 37,500 km3 that represents the theoretical supply of renewable fresh-
water each year. As much as half runs off the surface and to the sea in uncaptured floodwa-
ter. Humans build dams and other barriers to try to capture some of that runoff, but as we
will discuss, that brings its own problems and challenges. Another 20% of the 37,500 km3
of global freshwater supply is in regions that are not readily accessible. That leaves us with
roughly 12,500 km3 of what is known as reliable surface runoff, and it is this amount that
is actually available for human use and consumption. So how do we make use of this reliable
surface runoff? What are the environmental impacts of that use? And why do so many people
around the world still face water scarcity and shortages?

How Water Is Used
Because we use and rely on water in so many different ways, we can measure water consump-
tion differently as well. For starters, it’s estimated that humans already appropriate over half
of the 12,500 km3 of reliable surface runoff each year, leaving less than half for all other spe-
cies and organisms on the planet. We can first divide that human use or appropriation into
two broad categories: instream uses and extractive uses.

Instream uses of water refers to the ways in which we use water without actually extracting
it from its physical location. For example, water-based recreational activities like boating and
waterskiing are common on many lakes and rivers in countries like the United States. While
these activities do not involve a direct consumption of water, they may compete with or pre-
vent the use of that water for other purposes.

Extractive uses of water refers to situations in which water is physically removed from its
source location. In some cases this involves actual consumption, while others involve using
and then returning the water to its source. For example, when water is extracted from a river
or aquifer and used to irrigate a farm field, most of that water will evaporate to the atmo-
sphere. This represents a consumptive use of water. In contrast, hydroelectric power plants
divert large amounts of water from rivers and lakes to generate electricity (see Section 7.12),
but that water flows back to the same river or lake. This represents a nonconsumptive use
of water. The Apply Your Knowledge feature examines the environmental impact of noncon-
sumptive use.

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use?

You can probably imagine the environmental impacts of chemical pollution and water
consumption, but what about nonconsumptive water use?

To explore this question, consider the Brazilian Nuclear Power Plant (BNPP) in southeastern
Brazil. The facility withdraws water from Ilha Grande Bay to cool equipment. Afterward, that
water is returned to the bay. Aside from a small amount of water that is lost to evaporation,
no materials are added or removed during the process.


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Section 5.3 Global Water Use and Demand

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use? (continued)

In a 2012 study, researchers investigated the environmental impacts of BNPP on Ilha
Grande Bay (Teixeira, Neves, & Araújo, 2012). Researchers collected measurements of
fish biodiversity and abundance near the power plant (within 200 meters) and in similar
environments farther away (more than 1,500 meters). They then compared the two locations
to highlight any differences. Some of these results are shown in Figure 5.3.

Figure 5.3: Impact of BNPP on biodiversity and fish abundance

Species biodiversity (a) and fish abundance (b) in Ilha Grande Bay. “Close” locations are less
than 200 meters and “far” locations more than 1,500 meters from the BNPP facility.

Source: Data from “Thermal Impact of a Nuclear Power Plant in a Coastal Area in Southeastern Brazil: Effects of Heating and
Physical Structure on Benthic Cover and Fish Communities,” by T. P. Teixeira, L. M. Neves, and F. G. Araujo, 2012, Hydrobiologia,




































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Section 5.3 Global Water Use and Demand

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use? (continued)

The first chart suggests that there is significantly less biodiversity (fewer species of fish)
close to the power plant than there is farther away. In the second chart, the difference
between the two measurements is small compared with the uncertainties of the two
measurements. There appears to be a similar number of fish in both locations.

Take a moment to consider this data along with what you know about water use in this
location. Can you explain how the power plant might be impacting fish in the surrounding

The power plant is affecting ecosystems by altering environmental conditions. According
to the temperature data in the Ilha Grande Bay study, the water near BNPP is more than 4
degrees Celsius warmer than its surroundings (see Figure 5.4).

When the power plant cools off its equipment, the process warms the water that is extracted.
This raises the temperature of bay locations with close proximity to BNPP. While many fish
species can survive the cooler temperatures of the greater bay, relatively few have been able
to thrive close to the power plant. With less competition, the species that can tolerate the
warmer water are also able to achieve larger populations than they do elsewhere. The result
is an environment that still has life but that is severely diminished in terms of biodiversity.

Figure 5.4: Impact of BNPP on water temperature

Temperatures at Ilha Grande Bay study locations.

Source: Data from “Thermal Impact of a Nuclear Power Plant in a Coastal Area in Southeastern Brazil: Effects of Heating
and Physical Structure on Benthic Cover and Fish Communities,” by T. P. Teixeira, L. M. Neves, and F. G. Araujo, 2012,
Hydrobiologia, 684.













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Section 5.3 Global Water Use and Demand

Who Uses Water (and How Much)
Globally, agriculture is the largest user of water, accounting for about 70% of all extractive
water uses. However, this global average masks wide variations in water consumption by sec-
tor and in the overall amounts of water consumed. For example, in Africa and Asia agriculture
accounts for over 80% of all water use, whereas in more industrialized countries of Europe,
only 20% goes to agriculture while 60% goes to industry (Food and Agriculture Organiza-
tion of the United Nations, 2016). Figure 5.5 shows a breakdown of average water use in the
United States. But even within the United States, there can be significant variations in these
figures. Most water use in the more industrialized and populated regions of the Northeast is
for power plants, industry, and residential uses. In drier regions of the West and Southwest,
over 80% of water use is for agriculture (Dieter et al., 2018).

Per capita levels of water consumption also vary widely among different regions of the world
(see Table 5.1). This is partly a result of water supply and the infrastructure needed to deliver
that water to people when and where they need it. It’s also a function of factors like standard
of living, how efficiently water is used in that country, the kinds of economic activities under-
taken there, and the food choices people make. Water consumption generally increases with
standard of living, and countries that produce highly water-intensive products like cotton
and beef tend to have higher rates of per capita water use. This is one of the reasons why the
United States and Australia, both big producers and consumers of beef, have some of the high-
est rates of per capita water consumption in the world.

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use? (continued)

When industries like BNPP impact the environment by adding heat, we call it thermal
pollution. Thermal pollution affects both freshwater and marine ecosystems like the one in
Ilha Grande Bay. According to a recent study, the Mississippi River absorbs more heat from
nonconsumptive water use than any other river in the world. Meanwhile, the Rhine River in
Europe experiences the most significant temperature increases from thermal pollution of
any major river. Coal and nuclear power plants serve as the pollution sources in both cases
(Raptis, Van Vliet, & Pfister, 2016).

Thermal pollution is an example of a 21st-century environmental problem. Like many of
our most pressing issues, it is the result of complex human and environmental systems that
interact in sometimes unexpected ways. It demonstrates that we need to do more than just
reduce material flows if we want a sustainable future. We also need to understand systems
holistically and consider all the environmental factors that allow life to thrive.

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Section 5.3 Global Water Use and Demand

Figure 5.5: Water use in the United States

These pie charts show average water use across the United States, but the breakdown can vary
significantly by region.

Source: Adapted from “Summary of Estimated Water Use in the United States in 2015,” by US Geological Survey, 2018 (https://pubs.usgs
.gov/fs/2018/3035/fs20183035.pdf); adapted from “Residential End Uses of Water, Version 2,” by US Environmental Protection Agency
and Water Research Foundation, 2016 (https://www.waterrf.org/research/projects/residential-end-uses-water-version-2).

Water use in the United States,
by category (2015)

Household water use in the United States,
by activity (2016)




Industry and mining









Table 5.1: Annual per capita water use around the world (1996–2005)

Low (<1,000 m3) Medium (1,000–2,000 m3) High (>2,000 m3)

Bangladesh 769 South Africa 1,255 Israel 2,303

Rwanda 821 Japan 1,379 Australia 2,315

Nicaragua 912 Thailand 1,407 Canada 2,333

Malawi 936 Germany 1,426 Spain 2,461

Guatemala 983 France 1,786 United States 2,842

Note. 1 m3 = 264 gallons.

Source: Data from “The Water Footprint of Humanity, by A. Y. Hoekstra and M. M. Mekonnen, 2012, Proceedings of the National
Academy of Sciences, 109 (https://waterfootprint.org/en/resources/waterstat/national-water-footprint-statistics).

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Section 5.3 Global Water Use and Demand

The example of beef illustrates an important concept known as virtual water, or embodied
water. We may not think about it, but just about every item we use or consume required water
to produce. In terms of food items, for example, it takes roughly 15,415 liters (4,072 gallons)
of water to produce one kilogram of beef, and 1,608 liters (425 gallons) of water to produce
enough wheat for a kilogram of bread (see Figure 5.6). But water is also used to produce
nonfood items as well. For example, it takes roughly 5,400 liters (1,427 gallons) of water to
produce one pair of jeans. For comparison, we use about 75 to 100 liters (20 to 26 gallons) of
water for an average 10-minute shower.

Figure 5.6: Virtual water

This graph illustrates the liters of water needed to produce a kilogram of each of these food items. The
amount of water required to produce the food we eat is not always obvious.

Source: Data from “Product Gallery,” by Water Footprint Network, n.d. (https://waterfootprint.org/en/resources/interactive-tools/product































Liters of water

20,00010,000 15,0005,0000

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Section 5.3 Global Water Use and Demand

The virtual water concept helps illustrate how consumption decisions made in one location
can impact water supply and management issues in another. In recent years California has
been experiencing severe droughts and water shortages, and yet this state alone produces
over a third of America’s vegetables and two thirds of its fruits and nuts. It’s estimated that
the average American consumes over 1,100 liters (290 gallons) of California water every
week by eating food products grown there (Buchanan, Keller, & Park, 2015). The virtual water
concept also makes even clearer the problem of food loss and waste discussed in Chapter 4.
Every time we waste food, we are also wasting all the water (and energy; see Chapter 7) used
in the production of that food.

Challenges of Meeting Water Demand
Many regions of the world are already experiencing, or will soon experience, serious chal-
lenges in meeting their water needs. Water scarcity refers to a situation in which there is
a physical, volume-based lack of water. It’s estimated that close to 700 million people in 43
countries around the world currently experience water scarcity and that this number could
more than double in the next decade (United Nations Department of Economic and Social
Affairs [UNDESA], n.d.b). Water stress, in contrast, is a broader term that includes physi-
cal scarcity as well as issues of water quality and the accessibility or affordability of clean
water supplies. Over 1 billion people are currently experiencing water stress, and this figure
could grow as high as 4 billion in the decades ahead unless more effective and efficient water
management practices are implemented (UNDESA, n.d.b). Later sections in this chapter will
highlight ways we can address water scarcity and stress, as well as challenges related to water
quality. Before that, however, let’s have a look at some areas where meeting water demand is
proving difficult.

Water Rationing in South Africa
One of the most high-profile and recent examples of water scarcity is playing out in the city
of Cape Town, South Africa. Cape Town is a modern, bustling metropolis and a major tourist
destination located at the southern tip of the African continent. It has a population (4 million)
and climate similar to Los Angeles in Southern California.

After 3 years of severe drought and poor water management decisions, the city began to warn
residents and businesses in late 2017 of “Day Zero,” the day when municipal water would

Learn More: Your Water Footprint

There are a number of sources that allow you to explore and calculate your “water footprint”
in different ways.

• https://waterfootprint.org/en
• https://www.watercalculator.org
• https://water.usgs.gov/edu/activity-percapita.html

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Section 5.3 Global Water Use and Demand

be completely cut off and water would be
available only through centralized distribu-
tion points. Cape Town was set to become
the first modern major city in the world to
run dry.

Severe restrictions on residential and agri-
cultural water use and a return to more
normal rainfall patterns in the latter half of
2018 helped Cape Town postpone Day Zero,
but the water situation there is still precari-
ous. Residents are still limited to using 50
liters (13 gallons) of water per day, farms
outside the city have had their irrigation
supplies cut off, and long lines can still be
found at natural springs and grocery stores
when supplies of bottled water are deliv-

ered. Cape Town offers a cautionary tale of how even major cities can be at risk of water scar-
city, especially as global climate change alters precipitation patterns and weather.

Dams in China and the United States
One way to try to alleviate water scarcity and stress is through the construction of dams and
water diversion projects. Dams are built across rivers to capture and store surface runoff in
reservoirs. Dams can be utilized to control runoff to prevent floods, generate hydroelectric-
ity, and supply water for agricultural, industrial, and residential uses. There are over 800,000
dams around the world, including close to 50,000 “large dams” that are 15 meters (50 feet)
or higher. Combined, these dams capture and store close to 15% of global surface runoff for
human uses. In the United States that figure is closer to 50%.

While dams can provide many benefits in terms of water supply and management, energy
production, and recreation, they also have a number of problems associated with them. First,
when rivers are dammed, they create reservoirs behind the dam that can displace entire com-
munities. For example, China’s massive Three Gorges Dam (the largest in the world) displaced
1.2 million people and flooded 13 cities, 140 towns, and 1,350 villages. Second, dams can have
dramatic impacts on native fish and wildlife species as well as alter important ecosystem
functions and services that rivers provide. For example, a series of large dams on the Colorado
River have fundamentally altered that ecosystem and reduced the flow of water from that
river to the ocean to virtually a trickle.

Competing Water Use Along the Colorado
The Colorado River also offers an example of a regional water system threatened by misman-
agement, competing demands between users, and global climate change. The Colorado River
originates on the western slopes of the Rocky Mountains in Colorado. From there it flows
2,400 kilometers (1,500 miles) to the Gulf of California in Mexico. Along the way, the Colorado
River passes through mountain regions, deserts, and the Grand Canyon.

Bram Janssen/Associated Press
Residents of Cape Town, South Africa, waiting
in line for water. Water resources in Cape Town
are at a premium, and restrictions are in place
in response to severe water shortages.

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Section 5.3 Global Water Use and Demand

Almost 100 years ago, water managers in
western states began a systematic process
of building dams on the Colorado River
and using massive water diversion systems
to divide the river’s water between urban
areas and agriculture. Today nearly 40 mil-
lion people in cities such as Las Vegas, Phoe-
nix, Los Angeles, and San Diego depend on
water from the Colorado River, while over
70% of the water withdrawn is used to irri-
gate 1.4 million hectares (3.5 million acres)
of cropland that produces 15% of U.S. agri-
cultural products.

Since at least 2000, however, warning signs
have been flashing for Colorado River water
managers and others in the region. Water
levels in Lake Mead and Lake Powell (fed by the Colorado) have dropped dramatically, reveal-
ing water lines like “bathtub rings” that show where the water level used to be. Decreasing
winter snowfall totals in the Rocky Mountains, tied to global climate change, lead to reduced
runoff and water supply in the summer months. Water shortages in the region are projected
to get even worse with climate change, and water managers are already struggling to balance
competing demands for water from urban and residential users versus agricultural users.
Meanwhile, regional energy managers are making contingency plans for possible electricity
shortages caused by declining hydroelectric production from the region’s dams.

Water Diversion and the Aral Sea
An even more dramatic example of water misuse and mismanagement comes from central
Asia. The Aral Sea, located on the border between Kazakhstan and Uzbekistan, was once the
world’s fourth largest lake and roughly the size of the country of Ireland. Up until the 1960s
the Aral Sea supported hundreds of lakeside communities, provided an estimated 60,000 jobs
in the fishing industry, and provided important wildlife habitat and ecosystem services for
the region (Bennett, 2008).

At the time, the region was part of the Soviet Union, and Soviet engineers and planners made
the decision to divert water from two major rivers, the Syr Darya and the Amu Darya, that
fed freshwater to the Aral Sea. The water was to be used for irrigation for cotton and wheat
production. Dozens of large dams, almost 100 reservoirs, and over 30,000 kilometers (20,000
miles) of canals were constructed.

Gradually, the Aral Sea began to shrink in size, and by 2000 it split into a small northern por-
tion and a larger southern portion. A few years after that, the southern portion split again
into an eastern and western half. And in just the past few years, the southeastern portion has
dried up completely. Overall, the Aral Sea has lost over 90% of the water it once contained.
The former lakeside is littered with the rusted hulks of old fishing boats, and strong winds
whip up dust storms that blow over former lakeside communities and sicken whatever resi-
dents still remain.

Filippobnf/iStock /Getty Images Plus
Damming of the Colorado River has drastically
reduced the water level of Lake Mead. Here the
former water level is indicated by the bathtub-
like rings around the edges.

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Section 5.4 Water and Global Politics

Meeting the challenge of water demand is made all the more difficult because water is a
“transboundary” resource that moves across national borders and boundaries. This fact, com-
bined with rising populations and the threat of water shortages, has made water resources a
potential source of conflict between nations. This issue, and the idea of adequate water as a
fundamental human right, will be the focus of the next section.

5.4 Water and Global Politics

In 2010 the United Nations (UN) passed a resolution that explicitly recognized “safe and clean
drinking water and sanitation” (UN, n.d.c, p. 1) as fundamental human rights. The resolution
recognizes that drinking water supplies should be sufficient, safe, physically accessible, and
affordable (UNDESA, n.d.a). While the UN resolution does not specify what countries have to
do to meet this human right, it does call attention to the seriousness of the problem and estab-
lish a clear baseline of human water requirements at 50 to 100 liters (13 to 26 gallons) per
day. The UN cites research by WHO estimating that 24,000 children die every day from diar-
rhea and other preventable diseases caused by polluted water. This research also estimates
that millions of women and girls in developing countries walk an average of 6 kilometers
(almost 4 miles) every day to collect water for their families. This daily chore takes a physical
toll and prevents young girls from completing schooling that might improve their lives.

The UN resolution comes at a time when two global challenges could be exacerbating issues
of water availability and sanitation. As described in Chapter 3, global population is approach-
ing 8 billion and is projected to hit 10 billion later this century. Increased population means
increased water demand for direct and indirect (virtual water) uses, such as for agriculture.
In addition, global climate change (discussed in more detail in Chapter 8) is complicating

University of Maryland Global Land Cover Facility and NASA, Earth Observatory
The Aral Sea has lost over 90% of the water it once contained and has split into
several smaller seas. Before water diversion projects began in the 1960s, the Aral
Sea was the fourth-largest lake in the world. By 1989 (left), the northern and
southern part had begun to split. Between 2000 (middle) and 2009 (right), the
southern part dried up almost completely. Water levels have remained essentially
the same since 2009.

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Section 5.4 Water and Global Politics

the water supply picture. Climate change is lead-
ing to changing weather and precipitation patterns,
including more intense rains (and runoff) in short
periods and prolonged droughts in others. Cli-
mate change is shifting where and when precipita-
tion falls as well, making it difficult to predict and
manage water supplies for a growing population.
Finally, climate change and warming are leading
to increased evaporation from surface water sup-
plies and faster melting and retreat of major gla-
ciers around the world. At least 200 million people
depend almost exclusively on melting water from
glaciers for their water supply, and in some of these
places the glaciers are melting so fast that they are
at risk of disappearing.

This combination of population growth and global
climate change has led some experts to predict that
major wars of the 21st century are more likely to be
fought over water than any other resource, includ-
ing energy. While the link between water and con-
flict has a long history, current conditions appear to
be increasing the likelihood of future “water wars.”
There are 261 major river systems around the
world that cross national borders. When upstream
populations dam, divert, pollute, or somehow interfere with the quantity or quality of water
flowing downstream, there is the potential for conflict.

Currently, some of the most contentious regions where a water war is likely to break out
include the Nile River basin in Africa, the Euphrates–Tigris basin in the Middle East, and the
Mekong River basin in Southeast Asia. The Nile River flows through parts of 11 countries.
Dam construction in upstream countries like Ethiopia could result in tension and conflict
with downstream nations like Sudan and Egypt. In the Euphrates–Tigris basin, major water
diversion projects for irrigation in Turkey have affected river flow to Syria and Iraq. In the
Mekong River basin, upstream dam construction, particularly in China, has altered down-
stream water flows and ecosystems. China has used its political influence and power to ignore
complaints from other affected countries.

Even in the United States, there are numerous examples of legal conflict between states over
water rights and access. The most well known of these disputes involve management of and
access to Colorado River water in the arid Southwest. But even in the relatively wetter region
of the American Southeast, a 30-year conflict over water is playing out. The “tri-state water
wars” pit Alabama and Florida against Georgia over management of water from the Alabama-
Coosa-Tallapoosa (ACT) and Apalachicola-Chattahoochee-Flint (ACF) river basins. Upstream
Atlanta depends heavily on these river basins for meeting its municipal water needs, and
as the city’s population has grown, so has its use of these waters. In 1990 Alabama sued to
prevent Atlanta from taking additional water from lakes fed by the ACT and ACF river basins.
Eventually, Florida joined in the conflict, and in 2018 portions of the tri-state dispute reached
as high as the U.S. Supreme Court before being remanded to the lower courts.

The UN has deemed drinking water a
fundamental right. In many parts of
the world, women and girls must walk
miles each day to collect water for
basic needs.

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Section 5.5 Water Quality

Meeting the world’s demand for adequate water supplies needs to involve considerations of
supply, management, and the necessity of that demand. Further complicating the picture are
the issues of global climate change, discussed in Chapter 8, and water pollution, the focus of
the next section. One approach to better meeting regional water demand is through privatiza-
tion of water systems (see the Learn More feature box).

Learn More: Water Privatization

A somewhat controversial approach to managing municipal water systems is known as
water privatization. Typically, city and municipal water systems around the world have been
managed by government agencies or public utilities, whose primary goal was to deliver
adequate water to residents at the lowest cost possible. However, in some cities these
agencies and utilities were poorly managed and experienced high rates of water leaks and
wastage. As a result, water privatization was proposed as a solution. Privatization involves
selling water systems to private companies to manage on a for-profit basis.

Supporters of privatization argue that private sector companies are more efficient, are better
able to manage large-scale water supply systems, and have the financial capital to invest
in upgrades and other improvements to these systems. Critics argue that privatization is
a violation of the principle of water as a human right, since it makes water a commodity
that can be denied to individuals who lack the financial resources to pay for it. The reality
probably lies somewhere in between, with a lot depending on how privatization is handled
and what restrictions and requirements are placed on the company taking over a water

To learn more about water privatization and arguments for and against this approach, visit:

• https://blogs.ei.columbia.edu/2010/09/02/what-is-the-benefit-of-privatizing-

• https://pacinst.org/wp-content/uploads/2002/02/new_economy_of_water3.pdf
• https://www.foodandwaterwatch.org/insight/water-privatization-facts-and-

• https://www.citizen.org/wp-content/uploads/top10-reasonstoopposewaterpriva

• https://www.forbes.com/sites/adammillsap/2016/10/05/privatizing-water-


5.5 Water Quality

Up until this point most of our discussion has focused on issues of water supply and availabil-
ity, or water quantity. This section will take a closer look at the threats to water quality from
various forms of pollution and what’s being done to address it.

For as long as humans have lived in groups, they have diluted biological wastes by discarding
them in nearby streams, rivers, and other bodies of water. As human populations grew, and
as economic activity became increasingly industrialized and concentrated, the volume and
character of that waste also changed. However, the solution to pollution remained dilution,
and as a result, our waterways became more and more polluted over time.

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Section 5.5 Water Quality

In the United States this approach began to result in some dramatic and frightening examples
of water pollution by the 1950s and 1960s. For example, pollution of Lake Erie was so bad by
the 1960s that the lake was declared virtually dead and lifeless. In June 1969 the Cuyahoga
River in Cleveland, Ohio, caught fire due to buildup of oil and debris on the river’s surface.

News stories and headlines featuring these and other water pollution disasters helped result
in water-quality regulations that addressed some of the most glaring problems. However,
threats to water quality and new forms of water pollution continue to be a challenge. The EPA
(2016) recently completed a national assessment of rivers and streams. It reported that over
half of river and stream miles in the United States are severely polluted, impaired, or in poor
condition, meaning that those waterways did not meet federal water-quality standards.

Classifying Pollutants
The most basic breakdown of water pollution is between what are known as point sources
and nonpoint sources of pollutants (see Figure 5.7). Point sources are fixed and stationary
sources of water pollutants, such as a drainage pipe from a factory or discharge from a sew-
age treatment plant. Nonpoint sources are diffuse sources of pollution that are difficult to
pinpoint. For example, cow manure running off of a farm field, lawn chemicals washed off of
suburban lawns, and sediment washed into nearby streams and rivers from a construction
site are all cases of nonpoint source pollution.

Figure 5.7: Nonpoint vs. point sources of pollutants

Nonpoint sources of pollutants are diffuse and more difficult to manage, whereas point sources are fixed
and stationary.

Nonpoint sources Point sources

Car oil, trash, animal waste,
chemicals used on farms

and lawns can end up
in storm drains and

into bodies of water.

Factories, sewage treatment
plants, large-scale animal

feeding operations, and others
dispose of waste directly into

bodies of water.

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Section 5.5 Water Quality

Regardless of whether pollutants are from a point source or nonpoint source, they can be
further classified into different types. The most common are listed in Table 5.2. All of these
pollutants impair water quality in some fashion.

Table 5.2: Common types and sources of water pollutants

Type of pollutant Common sources

Pathogens Animal waste

Nutrients Fertilizers, CAFOs, sewage treatment plants

Sediment and soil Farms, construction sites

Oil Parking lots, tanker and pipeline spills

Plastics Litter, landfills

Heavy metals Industry

Toxic substances Pesticides, industry

Heat (thermal pollution) Power plants

Another type of water pollutant that is causing increased concern is chemical compounds in
items that we consume or use in our homes every day. For example, triclosan is an antibacte-
rial and antifungal agent used in soaps, toothpastes, deodorants, and lotions. This chemical is
washed down the drain and eventually enters rivers and streams, where it can be toxic to fish
and other aquatic life. Likewise, ecologists have measured detectable levels of birth control
hormones, antibiotics, caffeine, and other substances in hundreds of streams and rivers in
the United States. Because these chemicals are not removed from wastewater in most waste-
water treatment plants, they are excreted from our bodies and washed down drains before
entering rivers, streams, and other waterways. Once there they can have serious detrimental
impacts on fish and other forms of aquatic wildlife.

Managing Nonpoint Source Pollution
Managing nonpoint sources of water pollution is much more challenging than addressing
point source pollution because nonpoint pollution of a waterway can originate from hun-
dreds or even thousands of locations. After the high-profile water pollution disasters of the
1950s and 1960s, federal legislation was passed that targeted major point source polluters
like factories and sewage treatment plants. But water pollution from nonpoint sources like
agriculture (soil erosion, fertilizer runoff, manure runoff) and urban or suburban develop-
ment (lawn chemicals, parking lots and streets, sediment from construction projects) has
continued to worsen since then. In the example of New York City at the start of this chapter,
nonpoint sources were causing problems with the city’s drinking water supply.

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Section 5.5 Water Quality

One of the most serious types of nonpoint pollution from agriculture is runoff of animal
wastes and fertilizers, which can cause algal blooms, eutrophication, and aquatic dead zones.
To prevent runoff, water-quality experts encourage farmers to practice some of the sustain-
able agricultural techniques described in Chapter 4, including contour farming and low-till or
no-till agriculture. It also helps if farmers leave space for riparian buffers. A riparian buffer
is a vegetated strip of land alongside a stream or river. The trees, shrubs, grasses, and other
plants in a riparian buffer help trap soil, sediment, and other pollutants before they can enter
a waterway. In New York City part of the funding provided to upstate farmers was to help
establish and maintain riparian buffers in agricultural areas.

In urban and suburban areas, runoff of fertilizer from lawns, golf courses, and parks can also
contribute to eutrophication and dead zones. Large amounts of water and melting snow run-
ning off of roofs, streets, parking lots, and driveways can cause both water-quantity problems,
such as flooding, and water-quality problems as runoff picks up potential pollutants like road
salt and oil spilled from cars and trucks. Here too, establishing riparian buffers around urban
areas can help cut down on pollution entering waterways and slow the rate at which runoff
enters streams and rivers, reducing flood risks downstream. Protecting existing wetlands and
even establishing “constructed wetlands” that contain plants that can slow urban/suburban
runoff and absorb excess nutrients can also help minimize nonpoint source pollution. Other
approaches are outlined in Table 5.3. All of these approaches fall under the umbrella of water-
shed management, and they play an important part in the approach used to protect New York
City’s water supply. They also have in common the idea that it is better to try to prevent pollu-
tion from entering waterways in the first place than try to clean it up after it’s already there.

Table 5.3: Approaches for minimizing urban and suburban runoff

Approach Description

Riparian buffers Vegetated strips of land alongside streams and rivers

Green roofs A roof that is covered in plants and can absorb rainwater

Rain gardens A garden in a depressed area that collects rainwater

Permeable pavement A porous urban surface that allows rainwater to seep into the ground
instead of running off

Wetlands Swamps and marshes that contain plants that absorb nutrients and
improve water quality

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Section 5.5 Water Quality

One of the most challenging forms of water pollution involves contamination of groundwa-
ter supplies. Unlike surface water pollution, groundwater pollution is hidden from view and
potentially “out of sight and out of mind.” Groundwater pollution is also much more difficult
to clean up than surface water pollution. Whereas streams and rivers naturally flush them-
selves clear through running water, contaminants that enter groundwater get trapped there
and can take years or decades to break down or dissipate. Major sources of groundwater
pollution include leaks from industrial storage tanks, septic systems, and underground gaso-
line tanks, as well as seepage of agricultural chemicals like pesticides and fertilizers. In addi-
tion, hydraulic fracturing, or fracking, of oil and gas wells is increasingly being implicated in
the contamination of municipal and residential groundwater supplies in some regions of the
United States (see Learn More: Fracking and Water Quality).

Learn More: Fracking and Water Quality

Over the past couple of decades, there has been rapid development and growth in the use of
an oil- and gas-drilling technique known as hydraulic fracturing, or fracking. Fracking allows
oil and gas companies to remove these fuels from oil shale rock formations that previously
were not considered viable for exploitation (see Section 7.4). In fracking, liquids mixed
with sand (collectively known as fracking fluid) are pumped into oil shale deposits under
extremely high pressures. This fractures and cracks the shale formations while the sand
keeps the cracks open just enough to allow the oil and gas to begin to flow to the surface.

In theory, fracking should not have much of an impact on groundwater, since shale deposits
are located far below the surface and well below the water table and aquifers that homes
and municipalities draw drinking water from. However, the fracking process creates a
number of opportunities for groundwater contamination, and there is growing evidence that
this process has been impacting water quality in regions of the country where fracking is
widespread (including Pennsylvania, Wyoming, and Colorado). For example, leaks of fracking
fluid from the drill hole have been documented, as well as leaks of contaminated water that
“flows back” (known as flowback water) to the surface. Likewise, poor management and
handling of fracking fluid and flowback water at the well site can lead to spills and seepage of
these fluids into groundwater deposits.

The oil and gas industry has adamantly denied a link between fracking activities and changes
in water quality, while a major 2016 EPA report found that fracking could impact water
quality under “certain conditions” if the process is not managed properly. Nevertheless, as
fracking has grown in importance throughout the United States, and as well operations have
aged, the number of reports of water-quality impact from fracking activities has also grown.

More information on the links between fracking and water quality can be found at these

• https://www.epa.gov/hfstudy
• https://www.bbc.com/news/uk-37578189
• https://e360.yale.edu/features/as_fracking_booms_growing_concerns_about

• http://worldwater.org/wp-content/uploads/2013/07/ww8-ch4-fracking.pdf

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Section 5.5 Water Quality

There is also growing concern over groundwater contamination by a class of chemicals
known as per- and polyfluorinated alkyl substances, or PFAS. PFAS are used in a number of
products, including firefighting foam and waterproofing materials, and exposure to them has
been linked to various forms of cancer, pregnancy complications and low birth weights, liver
damage, thyroid disease, asthma, and reduced fertility. PFAS pollution is especially problem-
atic on dozens of military bases around the country due to heavy use there in firefighting
operations. The Union of Concerned Scientists (2018) reports that of 131 military sites tested
for PFAS in their groundwater used for drinking, only 1 was within the safe limit. Forty-three
sites had drinking water with PFAS levels that were 1 to 100 times over the safe limit, and 87
sites had PFAS levels more than 100 times greater than the safe limit.

Managing Point Source Pollution
Overall, serious water pollution problems
from point sources like factories have
become much less of a problem in countries
like the United States due to laws and regu-
lations. The U.S. Clean Water Act (CWA),
which was first passed in 1972, makes it ille-
gal for a factory or another point source to
dump any pollutant in a waterway without
a permit. The CWA also sets standards for
industrial wastewater management, places
restrictions on wetland destruction or con-
version, and provides funding mechanisms
for upgrading municipal wastewater treat-
ment plants. One interesting provision of
the CWA allows individual citizens and envi-
ronmental groups to monitor and report to
the federal government cases in which CWA
standards are not being met. This has led
to the formation of hundreds of volunteer
water-quality monitoring groups across the country that regularly test and report on water-
quality conditions in their area. Soon after the CWA was passed, the Safe Drinking Water
Act (SDWA) was enacted in 1974. The SDWA required that the EPA set specific standards for
allowable levels of chemicals in water and mandated that local water authorities monitor and
report on drinking water quality in their jurisdictions.

While the CWA and the SDWA have both resulted in dramatic improvements in water quality
in the United States since the 1970s, there remain significant challenges with water pollu-
tion, particularly from nonpoint sources. (If you’re interested in the quality of your own local
water supply, check out Close to Home: Assessing Local Drinking Water.) The remainder of this
chapter will focus on additional approaches both to conserve water and manage demand, as
well as on further ways in which water quality can be protected. This includes a discussion of
water conservation and management in Section 5.6 and the role that forests play in protecting
water supplies in Section 5.7.

Aaron Bacall/Cartoon Collections

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Section 5.5 Water Quality

Close to Home: Assessing Local Drinking Water

The Flint water crisis began in 2014 when the city of Flint, Michigan, changed its public
water sources from the Detroit River and Lake Huron to the Flint River. During the transition,
the city mismanaged how it was treating its water, and pipelines began releasing large
amounts of lead into the public water supply. More than 100,000 residents were exposed
to high levels of this heavy metal neurotoxin, including 6,000 to 12,000 children who may
suffer from lifelong health challenges as a result. A federal state of emergency was declared
in 2016, and ever since, officials have been scrambling to fix the problem.

The Flint water crisis demonstrates the high stakes involved with protecting public water
supplies. It also highlights the importance of regular water monitoring. In this feature box,
we will learn about some regulations that protect our water supplies. We will also take a
closer look at where our drinking water comes from and determine if it is safe to drink.

The SDWA of 1974 requires the mandatory monitoring of public water supplies throughout
the United States. Local water authorities must test drinking water for microorganisms,
disinfectants, and chemical pollutants like lead on an annual basis and publish their findings
in documents called Consumer Confidence Reports (CCRs). These reports provide background
information on local water systems as well as the detailed monitoring information of specific
pollutants. Table 5.4 is an excerpt from a 2017 CCR for Meadville, Pennsylvania.


Table 5.4: Excerpted 2017 water test results for Meadville, Pennsylvania


level MCLG

value Units


# of
AL of


Sources of con-

Lead 15 0 2 ppb 06/01/16 0 out
of 30

No Corrosion of
plumbing; ero-
sion of natural

Copper 1.3 1.3 0.5 ppm 06/01/16 0 out
of 30

No Corrosion of
plumbing; ero-
sion of natural
deposits; leach-
ing from wood

Source: From “2017 Annual Water Quality Report,” by Meadville Area Water Authority, 2017 (https://meadvillepa

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Section 5.6 Water Conservation and Management

5.6 Water Conservation and Management

Throughout the 20th century, the primary approach to meeting growing water needs and
demand was to build more dams, reservoirs, pipelines, and water treatment plants. The basic
idea was to deliver high-quality water to all end users and to eliminate wastewater. The result
was a highly centralized and industrial-scale approach to meeting water demand, one that
placed a large amount of political and economic power in the hands of water utilities.

Peter Gleick, a water scientist and cofounder of the Pacific Institute, has labeled this approach
the hard path for water because of its focus on physical infrastructure and water supply
projects. While Gleick acknowledges that hard path approaches have brought economic and
health benefits over the past 100-plus years, he argues that now is the time for a new approach
to water management. This new approach, a soft path for water, is meant to complement
and build on the success of established hard path infrastructure. But rather than building
new water supply and distribution systems, the soft path focuses on improving efficiency
and helping local communities take control of their own water needs (Gleick, 2010; Pacific
Institute Staff, 2013).

Close to Home: Assessing Local Drinking Water (continued)

This section of Meadville’s CCR presents the results of lead and copper monitoring. Three
columns, in particular, provide important information about the safety of this drinking water.
First, there is the maximum contaminant level goal (MCLG) for each pollutant. Depending on
the type of pollutant being measured, these values might also be called a maximum residual
disinfectant level goal (MRDLG). When pollutant levels are below these values, there is no
known risk to human health.

You may also notice the column providing an action level (AL) for each pollutant. This value
represents the enforceable standard for drinking water. In other words, the EPA requires
water authorities to take action when measurements exceed these levels. These levels may
also be listed on CCRs as maximum contaminant levels (MCLs) or a maximum residual
disinfectant levels (MRDLs). In general, these values are set as close to MCLGs and MRDLGs
as possible while taking technology and cost limitations into consideration.

Finally, the column labeled “# of sites above AL of total sites” tells us how many of the
locations sampled by the water authority exceeded the upper limits set by the government.
Luckily for the folks in Meadville, none of these sites appeared to have excessive amounts of
lead or copper.

Now that you have a better understanding of what drinking water information is available
and what it means, see if you can find a CCR for your location. You can often find them on the
Internet by using “Consumer Confidence Report” and the name of your hometown as search
terms. You can also obtain this information by reaching out to your local water authority. By
reading the CCR for your hometown, you will learn a little bit more about where your water
comes from and whether there are any contamination issues you should be concerned about.

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Section 5.6 Water Conservation and Management

Characteristics of the Soft Path
Gleick distinguishes the soft path for water from the hard path in a few different ways. First,
the soft path focuses on meeting the water-related needs of people, not just a certain level of
supply. People need water to clean clothes, irrigate crops, and shower, and if we can help them
find a way to do these things with less water, we should. For example, washing machines that
use half the water to wash clothes or irrigation systems that require one third of the water to
support crops are still allowing home owners and farmers to achieve the desired outcome at
a lower cost.

Second, the soft path pays more attention to matching water quality to specific end uses. For
example, water for irrigation or certain industrial uses does not have to be of the same quality
as water we use for drinking or bathing. As a result, soft path approaches often involve finding
ways to reuse water more than once before treating it, such as by diverting gray water—rela-
tively clean water from sinks and showers—to water plants or flush toilets.

Third, the soft path emphasizes smaller, decentralized solutions to water management issues.
Rather than invest massive amounts of scarce capital in new water supply systems, these
funds could be used to pay for hundreds of smaller scale initiatives at the local level that save
just as much or more water. For example, many water utilities promote and even make avail-
able, at low cost or no cost, water-conserving devices (such as low-flow showerheads and
rain barrels) and products to their customers.

Fourth, the soft path recognizes that water is as essential to the health of natural systems as it
is to human society. Therefore, soft path approaches seek to work with nature rather than try-
ing to engineer or work against it. This is precisely what New York City did when it invested
in the water purifying ecosystems in its water supply region.

Examples of the Soft Path
Soft path approaches to water management are becoming more common as opportunities
to develop new water supplies dwindle and as the cost of hard path approaches continues to
rise. In the 1970s Orange County, California, was one of the first locations in the United States
to experiment with treated wastewater reuse. At the time, the Orange County Water District
was pumping water out of its main aquifer faster than it could recharge, and as a result salt
water from the nearby Pacific Ocean was seeping into the aquifer. The water district also
imported water from the Colorado River and the Sierra Nevada mountain range, but that sup-
ply was limited and costly. A decision was made to take municipal wastewater—the water left
over after sewage is treated—and pump it into holding ponds directly above the municipal
aquifer. This wastewater slowly seeps into the aquifer below, which helps maintain water lev-
els and supply. Because soil can naturally filter any remaining contaminants from the water,
this approach also maintains the quality of Orange County’s main aquifer. Orange County’s
wastewater-to-drinking-water facility (known as the Groundwater Replenishment System) is
now the world’s largest, and with an upcoming expansion scheduled to begin in late 2019, it
will provide close to 500 million liters (130 million gallons) of drinking water a day and meet
40% of the district’s overall demand.

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Section 5.6 Water Conservation and Management

In addition to wastewater reuse, local water authorities are adopting other soft path
approaches. For example, Los Angeles and other cities in Southern California used to try to
prevent flooding by building concrete drainage channels to carry storm water straight to the
ocean. Today these cities are making changes to road surfaces, city parks, and other built-up
areas to slow storm water runoff and increase rates of recharge to underground aquifers.
These are examples of the soft path approach of working with nature.

Cities in the eastern United States that have older water distribution systems are increasing
efforts aimed at leak detection and repair. The WRI estimates that up to 50% of all the water
“captured” by water supply systems in the United States is lost to evaporation, leaks, and
inefficient use. Basic investments in leak detection and repair can cut these losses dramati-
cally and save water districts and their customers millions of dollars. Elsewhere, especially in
drought-prone regions of the Southwest, water districts are working with local residents to
help them cut water use for landscaping, bathing, toilets, and other purposes (see Figure 5.8).
It costs the water district less to help a customer cut water demand than it does for the water
district to increase water supply.

Given that agriculture is the single biggest user of water globally, improving water use effi-
ciency in this sector is an important part of the soft path approach. The most basic and inef-
ficient form of crop irrigation is known as flood irrigation. This involves pumping water from
a river or underground aquifer and allowing it to flow across a farm field. Likewise, spray
irrigation uses large-scale sprinklers to spray large amounts of water on a field. Both methods
lose as much as half the water they spread through evaporation and runoff. Far more efficient
methods for crop irrigation are available and have come into wider use in recent years as
farmers become more aware of water supply challenges. Low-energy, precision application
sprinklers, drip irrigation systems, and center-pivot, low-pressure sprinklers all deliver 80%
to 95% of the water used to the plants where they need it. Small-scale farmers in develop-
ing countries are also increasingly returning to water conservation practices and approaches
that were once more common. These include rainwater harvesting and the construction of
simple “check dams” built across water channels to slow runoff and increase water infiltra-
tion to aquifers. Even small improvements in the efficiency of water use in agriculture can go
a long way to help free up water supplies for thirsty cities like Cape Town, South Africa.

Learn More: Orange County’s Soft Path Approach

More information about the innovative groundwater replenishment system in Orange
County, California, can be found here.

• https://www.ocwd.com/what-we-do/water-reuse
• https://www.ocwd.com/gwrs

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Section 5.6 Water Conservation and Management

Figure 5.8: Water efficiency tips

Where else can you save water?

Source: Adapted from artisticco/iStock/Getty Images Plus

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Section 5.7 Forests and Water Management

Soft path approaches to meeting water demand represent a move toward integrated water
resources management (IWRM). IWRM looks at issues of water supply and water demand
holistically and in an integrated manner, rather than treating them as separate matters to be
addressed by different agencies and organizations. What soft path approaches and IWRM
have in common is that they tend to put more emphasis on local solutions to local challenges,
rather than relying, for example, on the construction of new dams hundreds of miles away to
meet water supply shortages. Given the increasing challenge of meeting world water needs in
a time of rising populations and global climate change, such local approaches may be the best
option for avoiding severe water shortages and conflict.

The final section of this chapter shifts to a focus on the role of forests and forest ecosystems in
maintaining both water quantity and water quality. As we saw with the example of New York
City’s water system, forested ecosystems help replenish water sources and purify water as it
enters reservoirs, rivers, and streams.

5.7 Forests and Water Management

It may seem odd to have a section on forests in a chapter on water, but effective forest man-
agement plays a critical role in good water management. Forests provide ecosystem functions
and services that affect both water quality and water quantity. In a sense, forests are a form of
natural infrastructure that can be just as important—or even more important—to water qual-
ity and quantity as the physical infrastructure of dams, pipelines, and water treatment plants.

Maintaining Water Quantity
As rains fall and snow melts, forests help slow the rate at which water runs off the surface.
Tree roots and dead branches and leaves on the ground intercept water and hold it, allowing it
to slowly seep into the ground. Some of this water recharges underground aquifers, while the
rest is slowly released into nearby streams and riv-
ers. Experiments at the Hubbard Brook Experimen-
tal Forest in New Hampshire and at other locations
have been designed to measure what happens to
stream flow when forests are cleared (Franz, 2016).
In one experiment after another, water runoff and
stream flow increased dramatically after trees
were removed, resulting in a stream flow pattern
that spikes immediately after rains or snow melt
(increasing the risk of floods) and then drops dra-
matically soon after. In contrast, when forests are
intact, water from rains and snow melt is released
slowly to underground aquifers and nearby streams,
and stream flow patterns are more steady and reli-
able. In fact, it’s typically the case that even after
weeks of no rain or precipitation, forest streams are
still flowing with significant volumes of water.

Cleared forest land—such as the
deforestation in the Amazon shown
here—can create sediment loading in
nearby streams and rivers, creating
water-quality issues for communities
farther downstream.

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Section 5.7 Forests and Water Management

Maintaining Water Quality
In addition to maintaining water quantity, forests also help maintain water quality. The Hub-
bard Brook experiments have shown that water running off cleared forest land is high in
nitrates and other pollutants and does not meet clean drinking water standards. Clearing for-
ests also increases soil erosion and “sediment-loading” of streams and rivers, increasing the
costs of water treatment for downstream communities. In contrast, intact forests help pre-
vent soil erosion and can also help trap and hold other pollutants and contaminants before
they can enter nearby waters. This is why riparian buffers—discussed in Section 5.5—are so
important to water quality.

The example of New York City’s water system at the start of this chapter helps illustrate the
importance of forests in good water management. Another example comes from Rio de Janeiro
in Brazil, site of the 2016 Summer Olympics. Rio operates the world’s largest water treatment
plant to provide clean water to its 6.3 million residents. However, this treatment facility is
facing operating challenges due to deforestation that is occurring upstream from the city.
The deforestation is increasing rates of soil erosion and leading to increased sediment in the
water as it reaches Rio’s reservoirs. Like New York, Rio is approaching this challenge not by
constructing more or better water treatment plants but by going to the source of the problem
in upstream watersheds. The strategy is to restore and maintain upstream forested areas, an
approach that will save the city an estimated $79 million in water treatment costs annually
while also improving water quality (Ozment & Feltran-Barbieri, 2018).

Maintaining the Global Water Cycle
In addition to their direct and immediate impact on water quality and quantity in nearby eco-
systems, we are also becoming more aware of the critical role that forests play in maintaining
the global water cycle. Trees and other plants perform the ecosystem service of drawing water
from the soil and releasing it to the atmosphere as water vapor through transpiration. This
process has been summed up beautifully by environmental journalist Fred Pearce (2018a):

Every tree in the forest is a fountain, sucking water out of the ground through its
roots and releasing water vapor into the atmosphere through pores in its foli-
age. In their billions, they create giant rivers of water in the air—rivers that form
clouds and create rainfall hundreds or even thousands of miles away. (para. 1)

Those “giant rivers of water in the air” are disrupted through deforestation, especially large-
scale tropical deforestation. Deforestation in the Amazon basin could disrupt precipitation
patterns and agriculture in China and central Asia thousands of miles away.

As a result, any discussion of effective and sustainable water management should also include
ideas for sustainable forest management. In forested, tropical regions of South America,
Africa, and Southeast Asia, this often involves efforts at community-based forest manage-
ment. Rather than fencing off forests as a means of protecting them, these programs work
with local communities to help them derive a livelihood from the forests while also managing
them sustainably. Rain forest–certified coffee, chocolate, and other products are examples of
items that can be produced in a way that maintains the ecological integrity and ecosystem
services of forested regions.

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Bringing It All Together

Bringing It All Together

It’s somewhat remarkable that water is so essential to human life yet many of us barely even
think of it. We turn on the tap or shower, flush the toilet, and consume water-intensive fruits
and vegetables with barely a thought to where that water came from or where it goes after
we use it. This is partly a function of where and how we live. For example, where this book’s
authors live in northwestern Pennsylvania, it seems like sometimes there is too much water.
As a result, it can be hard to appreciate notions of water as “scarce” or “precious.” In con-
trast, residents of places like California and Cape Town, South Africa, who have lived through
years of crippling drought and water shortages, are more likely to pay closer attention to
their own water use patterns. Even more so, a woman or young girl in a water-scarce or
water-stressed region of the developing world will be acutely aware of the value of water if
she has to walk long distances every day to acquire it.

Despite an evolving awareness and growing evidence of the challenges of meeting water
demands in a time of population growth and global climate change, we are still largely
approaching water and forest management in ways that are problematic. Hard path
approaches that dominated water management throughout the 20th century are bumping
up against physical, financial, and ecological limits. Soft path approaches are becoming more
widely adopted but perhaps not as quickly as needed. A more rapid move toward soft path
and integrated water resource management approaches is called for, one that looks at issues
of water supply, demand, access and human rights, ecosystem management, and trans-
boundary political cooperation as interconnected rather than separate.

While this chapter dealt with that small portion of the planet’s water that is fresh, the next
chapter will examine the challenges of sustaining the oceans that cover over 70% of the
Earth’s surface. We will see, perhaps not surprisingly, that some of the same issues that
make management of freshwater resources a challenge also apply to the oceans. We’ll also
see that a growing awareness of the importance of oceans to all life is driving innovative
approaches to sustaining this remarkable and vast resource.

Additional Resources

Global Water Use and Demand

The Yale Environment 360 website features an excellent five-part series, “Crisis on the
Colorado,” that examines the threats to the Colorado River system and the communities that
depend on its water.

• https://e360.yale.edu/series/crisis-on-the-colorado

National Public Radio featured a series of stories called “Stories From the Water Front” that
focused on communities struggling with water supply and water-quality issues.

• https://www.npr.org/series/646816049/stories-from-the-water-front

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Bringing It All Together

There are a number of interesting TED Talks on water shortages. Here are some good

• Balsher Singh Sindhu: Are We Running Out of Clean Water?:

• Anu Sridharan: When Will I Get My Water Next?:

• Kala Fleming: Easing Water Scarcity by Understanding When and Where It Flows:

The World Resources Institute is an excellent source for information on global water issues.

• https://www.wri.org/our-work/topics/water

The New York Times has a stunning video essay on how global warming is causing glaciers to
retreat in central Asia and what that will mean for local water supply.

• https://www.nytimes.com/interactive/2019/04/17/climate/melting-glaciers

Water and Global Politics

The issue of water shortages and the possibility of conflict between nations over water sup-
plies is growing in importance. These sources take a look at potential cases of water conflict
and what might be done to avoid them.

• https://e360.yale.edu/features/mideast_water_wars_in_iraq_a_battle_for

• http://worldwater.org/wp-content/uploads/2013/07/www8-water-conflict

• http://worldwater.org/wp-content/uploads/2013/07/ww8-ch1-us-water

• https://www.wri.org/blog/2018/11/un-security-council-examines-connection

Water Quality

In a humorous TED Talk, Rose George talks about the issue of a basic, sanitary toilet and the
implications for water quality.

• https://www.youtube.com/watch?v=ZmSF9gVz9pg

Water Conservation and Management

In this TED Talk, Lana Mazahreh talks about water conservation lessons learned while grow-
ing up in Jordan.

• https://www.youtube.com/watch?v=nLB8A—QdHc

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Bringing It All Together

As water shortages become more widespread and severe, there is increasing interest in the
idea of developing “toilet-to-tap” schemes that would purify and reuse water from toilets
and other water washed down the drain. This water is variously known as “gray water” if
it’s from sinks or showers and “brown water” or “black water” if it’s from toilets. As much
as people are taken aback by the idea of “toilet-to-tap,” plans are underway to do just that in
cities around the world, including San Diego, California.

• https://www.mnn.com/lifestyle/recycling/blogs/taste-recycled-waste-water
• https://sites.sandiego.edu/sdpollutiontrackers/2018/05/09/toilet-to-tap-not-as

• https://www.kusi.com/toilet-tap-moving-ahead-san-diego?
• http://www.bbc.com/future/story/20160105-why-we-will-all-one-day-drink

• https://www.sciencedaily.com/releases/2018/03/180313084219.htm
• https://www.pureblue.org/post/toilet-to-tap

Forests and Water Management

The connection between forests and water is the focus of these sites.

• https://www.americanforests.org/blog/the-important-relationship-between

• http://www.fao.org/3/a1598e/a1598e02.htm
• https://www.srs.fs.usda.gov/cifs/research/forests-and-water

Key Terms
aquifer An area of permeable rock and
sediment from which water can be extracted.

Clean Water Act (CWA) U.S. legislation
passed in 1972 that makes it illegal for a
factory or another point source to dump any
pollutant in a waterway without a permit.

community-based forest
management Programs that work
with local communities to help them
derive a livelihood from forests while
managing them sustainably.

consumptive use An extractive use
of water that involves withdrawing
the water and using it without
returning it to its source.

ecosystem management In the case
of water, an approach that focuses on
maintaining water quality at the source
rather than cleaning it at its destination.

evapotranspiration The process of
evaporation and transpiration together.

extractive uses The ways water
is used in which it is physically
removed from its source.

hard path for water A term coined
by water scientist Peter Gleick for the
traditional, centralized, and industrial-scale
water management approach. It typically
involves building distant dams, reservoirs,
pipelines, and water treatment plants.

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Toilet to Tap – Not as Horrendous as You’d Think!

Toilet to Tap – Not as Horrendous as You’d Think!

‘Toilet to Tap’ is moving ahead in San Diego










Bringing It All Together

hydrologic cycle The movement of
water between the planet’s surface,
atmosphere, soil, oceans, and living
organisms. Also known as the water cycle.

infiltration The process by which water
sinks slowly down through the soil.

instream uses The ways water is used in
which it is not removed from its source.

nonconsumptive use An extractive use
of water that involves withdrawing the
water and returning it to its source.

nonpoint sources Indirect and
diffuse sources of water pollutants.

point sources Stationary and fixed
sources of water pollutants.

reliable surface runoff Freshwater
runoff that is readily accessible for
human use and consumption.

riparian buffer A vegetated strip of
land alongside a stream or river.

Safe Drinking Water Act (SDWA) U.S.
legislation passed in 1974 that requires
that the EPA set specific standards for
allowable levels of chemicals in water
and mandates that local water authorities
monitor and report on drinking water
quality in their jurisdictions.

saltwater intrusion The movement of
saltwater into freshwater aquifers.

soft path for water A term coined
by water scientist Peter Gleick for an
alternative approach to water management.
It emphasizes improving efficiency and
local solutions over building new water
supply and distribution systems.

surface water Water on the
surface of the Earth, found in rivers,
wetlands, lakes, or reservoirs.

virtual water The water required
to produce a product or item before
it reaches the consumer. Also
known as embodied water.

water scarcity A physical lack of water.

watershed An area of land where
sources of water (streams, creeks) flow
together to a single destination.

water stress A lack of accessible
or affordable clean water.

water table A depth below
ground where soil and rock are
completely saturated with water.

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6 Sustaining Our Oceans

vladoskan/iStock /Getty Images Plus

Learning Outcomes

After reading this chapter, you should be able to

• Describe the different types and the importance of ocean currents.
• Describe the different types of coastal and marine ecosystems and the role they play in

providing ecosystem functions and services.
• Describe the different types of ocean pollution.
• Identify and analyze other major threats to our oceans.
• Describe different approaches to sustainable management of oceans.

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We already know that all living organisms need nutrients to survive. In particular, the nutri-
ents nitrogen and phosphorous are often a limiting factor in plant growth and productivity.
For remote, forested regions of the Pacific Northwest of the United States, a major source of
these nutrients is the Pacific Ocean, located hundreds of miles away. How does nitrogen and
phosphorous from the ocean reach these forested ecosystems? And how have scientists been
able to determine that these nutrients originated from the ocean in the first place?

The health of forests in the Pacific Northwest
is in fact closely connected with the salmon
that spawn and lay their eggs in the streams
and rivers of those forests. Salmon are a
type of anadromous fish, meaning that they
are born in freshwater ecosystems; migrate
to the ocean, where they spend most of
their lives (typically 3 to 8 years); and then
return to the same freshwater ecosystems
to lay their eggs. These return migrations or
“salmon runs” involve millions of fish swim-
ming hundreds of miles upstream. Some
salmon are caught and eaten by bears and
other animals along the journey, while oth-
ers reach their destination, lay their eggs,
and die. The salmon carcasses are eaten by
birds, bears, and other mammals and even-
tually even by salmon fry (baby salmon) when they emerge from their eggs. These salmon fry
then make their way to the ocean to begin the cycle all over again.

Because salmon gain 90% or more of their body weight while living in the ocean, they essen-
tially bring nutrients from the ocean to their spawning grounds. Birds, bears, and other
animals that eat these salmon carry those nutrients deeper into the forest and make them
available to plants when they defecate or die. Scientists use a technique known as stable iso-
tope analysis to determine the origins of nitrogen, phosphorous, carbon and other nutrients
found in trees, bear bones, and other organic material found in the forests of the Pacific North-
west. In some cases as much as 60% of critical nutrients like nitrogen found in these forests
are of a marine origin, suggesting that salmon are acting as huge “pumps” or “recyclers” of
nutrients to forests in these regions (Cederholm, Kunze, Murota, & Sibatani, 1999). How-
ever, overharvesting of salmon and the construction of dams and other barriers that obstruct
salmon runs have resulted in far fewer salmon reaching inland forests than ever before. As a
result, some of these forests are being starved of nutrients as the numbers of salmon, a key-
stone species in these ecosystems, decline.

The connection between salmon and inland forest ecosystems is just one example of the
many links between life on land and life in the oceans. Oceans are a critical form of natural
capital, and they provide numerous ecosystem functions and services that create or improve
conditions for life on land. For example, ocean currents carry warm water and air from tropi-
cal regions to higher latitudes and create favorable climate conditions for human settlement.

sekarb/iStock/Getty Images Plus
Salmon swim upstream to their spawning
grounds. Although the fish pictured are in
Alaska, their journey is not unlike those in the
Pacific Northwest.

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Section 6.1 Ocean Currents

Oceans also play a critical role in the carbon cycle and impact global climate. Evaporation
from ocean waters contributes up to 40% of freshwater rainfall over land surfaces each year.
And oceans are a major source of food for humans, a place of recreation and enjoyment, and
a habitat for over half of all life found on Earth.

Despite their importance, we know relatively little about ocean ecosystems compared with
life on land. Because the oceans are so vast and in some cases inaccessible, they represent
something of a final frontier for exploration and scientific research on this planet. And
because ocean ecosystems are mostly out of sight, we don’t always understand or appreciate
how our actions influence the health and productivity of this critical form of natural capital.
This chapter will provide an overview of ocean currents and major ocean and marine ecosys-
tems before shifting to major threats to the health of our oceans and the various approaches
to protecting and sustaining them.

6.1 Ocean Currents

The world’s oceans cover over 70% of the Earth’s surface and contain over 97% of all water
on the planet. All the major oceans are connected and essentially form one giant mass of
water. However, scientists divide the world’s oceans into five areas: the Atlantic, the Pacific,
the Indian, the Arctic, and the Southern (or Antarctic) Oceans. The Pacific Ocean is the largest
of these, covering almost one third of the Earth’s surface and containing over half of all the
water on the planet.

Because the oceans cover so much of the Earth’s surface, they absorb a significant amount of
incoming solar radiation. This radiation heats the oceans and helps drive a number of pro-
cesses (like wind and waves) that result in ocean currents. Ocean currents, in turn, move vast
amounts of water—and the heat that water contains—around the planet.

Types of Currents
Surface currents move water horizontally along the surface of the ocean, while vertical cur-
rents move water between the surface and the deep depths of the oceans.

Surface Currents
Surface currents are driven by a combination of the Earth’s rotation, winds, and differences in
water temperature. In the tropical regions of the Atlantic Ocean, near the equator, the prevail-
ing winds blow from east to west, pushing surface water west. Farther north, in the midlati-
tudes, the prevailing winds blow from west to east, pushing surface ocean water east. These
two wind-driven movements of water in opposite directions set up what is known as a gyre,
or a large-scale circular ocean current.

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Section 6.1 Ocean Currents

In the North Atlantic the gyre moves in a clockwise fashion as tropical currents move water
from Africa toward Central America and the Caribbean, and midlatitude currents move water
from the eastern coast of the United States toward Europe (see Figure 6.1). Further enhanc-
ing and contributing to this clockwise movement of ocean water in the North Atlantic is the
Coriolis effect. As the Earth rotates from west to east, winds are deflected to the right in
the Northern Hemisphere and to the left in the Southern Hemisphere. This sets up clock-
wise gyres in the North Atlantic and North Pacific Oceans and sets up counterclockwise gyres
in the South Atlantic, South Pacific, and Indian Oceans. The clockwise North Atlantic gyre is
what drives the Gulf Stream, the major ocean current that brings warm water from the tropi-
cal regions around Florida and the Gulf of Mexico to the northeastern United States, north-
eastern Canada, and northern Europe.

Figure 6.1: Major ocean gyres

Prevailing winds combined with the Earth’s rotation (Coriolis effect) create large-scale circular ocean
currents known as gyres. In the Northern Hemisphere ocean gyres move in a clockwise fashion. In the
Southern Hemisphere they move in a counterclockwise fashion.

Source: Adapted from “What Is a Gyre?” by National Oceanic and Atmospheric Administration, 2018 (https://oceanservice.noaa.gov/facts










Antarctic circumpolar current

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Section 6.1 Ocean Currents

Vertical Currents
Vertical currents are caused by differences in the temperature and salinity of ocean water. As
ocean water becomes colder, it also becomes saltier, and saltier water is denser and heavier
than less salty water. In the North Atlantic, as warm water moves from tropical regions near
the Gulf of Mexico northward toward Canada and Europe, it becomes colder and denser. This
increased density causes that water to sink and flow south again in a deep ocean current,
allowing more warm water to flow into its place from behind before that water also cools and
sinks. This vertical movement of water caused by differences in temperature and salinity is
referred to as the thermohaline circulation.

The combination of surface currents and vertical currents results in a massive global circula-
tion of ocean water known as “the ocean conveyor belt” or “the great ocean current” (see Fig-
ure 6.2). Whereas surface currents can move a molecule of water many miles in one day, the
thermohaline circulation in deep ocean currents is a much slower process, sometimes taking
hundreds of years to move a water molecule through a full global circuit.

Figure 6.2: The ocean conveyor belt

The combination of surface currents and vertical currents results in a great ocean current that plays a
key role in moderating weather conditions around the globe.

Source: Adapted from “Physics Division Annual Report,” by Argonne National Laboratory, 2001, p. 1 (https://publications.anl.gov
/anlpubs/2002/09/44218.pdf ).



w wat

Cold, salty, de
ep w


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Section 6.1 Ocean Currents

Impact on Weather
Another example of how ocean currents can affect our lives on land involves the El Niño–
Southern Oscillation (ENSO). Under normal conditions in the tropical Pacific Ocean, the
prevailing winds blow from east to west. These winds push warm surface water from the
western coast of South America toward Southeast Asia and the western Pacific region. This
warm water builds up in the western Pacific and results in higher rates of evaporation and
rainfall in places like the Philippines, Indonesia, and Vietnam. As surface water is pushed
from east to west, it also allows colder water from the deep ocean to be pulled up to the
surface along the western coast of South America—again, much like a conveyor belt. This
upwelling of relatively nutrient-rich deep water results in ideal conditions for fisheries along
the western coast of South America.

However, every 3 to 7 years this “normal” setup breaks down. ENSO refers to a situation in
which those east-to-west winds weaken and warm surface waters collect in the central and
eastern Pacific rather than the western Pacific. As a result, for 1 to 2 years, regions in the
western Pacific that normally get a lot of rain instead experience drought, whereas typically
dry regions along the western coast of North and South America experience heavy rains. Also,
because the east-to-west surface current comes to a halt, the upwelling of nutrient-rich cold
water along the coast of South America slows or ceases, and fishery productivity drops with
it. Furthermore, altered cloud formations and atmospheric conditions in the tropical Pacific
trigger a series of changes that shift weather patterns thousands of miles away. For example,
in the United States, ENSO years typically result in heavier rainfall and snowfall along the

Learn More: Melting Ice and Disruption of Ocean Currents

In the North Atlantic, thermohaline circulation is what creates the Gulf Stream, and the
Gulf Stream plays a critical role in carrying warmth and creating more moderate weather
conditions in the northern regions of Europe.

However, climate scientists are now worried that the Gulf Stream conveyor belt could be
slowing down and that this could plunge northern Europe into frigid conditions. The reason
for this, ironically, is global warming. Global warming has resulted in a dramatic increase
in the melting of Greenland’s ice sheets. As more and more freshwater from these melting
ice sheets enters the North Atlantic, it mixes with the salt water and makes it less salty
and thus less dense. This could be slowing the rate at which this water sinks, thereby also
slowing the rate at which warm water is pulled up from behind to replace it. The result could
be a slowing of the Gulf Stream and a reduction in the amount of heat energy it carries to
northern Europe.

This article from Yale Environment 360 helps explain the research and scientific debate
behind this phenomenon.

• https://e360.yale.edu/features/will_climate_change_jam_the_global_ocean

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Section 6.2 Coastal and Marine Ecosystems

West Coast, warmer and drier conditions in the North, and cooler and wetter conditions in
the South.

The movement of water through the Gulf Stream and the disruption of weather patterns
caused by ENSO demonstrate just how closely linked life on land is with what’s happening in
the oceans. We’ll see in Chapter 8 that there is growing concern among scientists that human-
induced climate change could be impacting oceans in ways that could actually modify ocean
currents. Such a shift in ocean currents could have profound effects on climate and weather
conditions in highly populated and developed regions of the world and could lead to major
disruptions in agriculture, transport, and other critical economic activities.

6.2 Coastal and Marine Ecosystems

Long before there was any life on land, living organisms evolved and flourished in the world’s
oceans. Today the oceans are home to hundreds of thousands if not millions of species, with
as many as 90% of them yet to be named and classified. The largest animal in the world, the
blue whale, calls the ocean home, and these creatures can grow to 30 meters (100 feet) in
length and weigh up to 181 metric tons. Yet it is the smallest of marine creatures, phyto-
plankton, that directly or indirectly sustains almost all life in the oceans. The surface waters
of the world’s oceans are teeming with billions and billions of phytoplankton, microscopic
algae that can photosynthesize just like trees and other land-based plants. Phytoplankton
form the base of the marine food web and are responsible for producing 50% to 85% of the
oxygen on the planet. (Recall that one by-product of photosynthesis is oxygen.) Phytoplank-
ton are eaten by larger microorganisms known as zooplankton, and zooplankton are eaten by
even larger organisms, including fish and marine mammals. Just as land-based plants form
the base of nearly all terrestrial food webs, these tiny “plants of the sea” are what support
nearly all life in the oceans.

Waste products, including dead carcasses of plankton, fish, and other marine organisms, are
constantly sinking toward the ocean floor. This slowly sinking shower of organic material
is known as marine snow, and it plays an important role in maintaining life in marine eco-
systems. Marine snow helps carry energy, captured by phytoplankton through photosynthe-
sis, from light-rich surface waters to the increasingly dark depths below. Marine snow is an
important food source for bottom-dwelling species of fish, crabs, and other organisms. And
in much the same way that nutrients cycle on land, the nutrients contained in marine snow
get cycled back to the surface through upwelling currents that carry cold water from the
deep back to the surface. This is why fisheries off the western coast of South America tend to
decline during ENSO events when upwelling currents slow down. Fewer nutrients being car-
ried to the surface means fewer phytoplankton (remember, these ocean plants need nutrients
just like other plants), and fewer phytoplankton means fewer fish.

Given the vastness and variety of conditions found across the world’s oceans, scientists divide
them into different zones and habitats. The most basic distinction is between three different
zones: intertidal, benthic, and pelagic (see Figure 6.3).

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Section 6.2 Coastal and Marine Ecosystems

Intertidal Zone
The intertidal zone occurs where oceans meet the land, specifically between the highest lev-
els of high tide and the lowest levels of low tide. Abundant light, nutrients, and oxygen tend to
make intertidal areas both highly productive and characterized by a high diversity of species,
but constantly shifting conditions and wave action also make life here challenging. Organisms
that live in intertidal zones—such as barnacles, mussels, oysters, seaweed, crabs, and sea
stars—must be able to tolerate a constant cycle of being either underwater or exposed to the
air, sun, and waves. Some organisms do this by anchoring themselves to rocks, while others
constantly move about and burrow under sand and rocks for protection.

Examples of critical ecosystems that are found in the intertidal zone area include estuaries,
salt marshes, and mangrove forests.

Estuaries and Salt Marshes
Estuaries are bodies of water in which freshwater from rivers mixes with salt water from
the sea. Most estuaries at temperate latitudes are salt marshes, shallow wetlands that are
flooded with salt water during high tides. Estuaries and salt marshes are highly productive

Figure 6.3: Oceanic zones

The ocean can be divided into three basic zones: intertidal, benthic, and pelagic. The pelagic zone can be
further subdivided into the photic and aphotic zones, based on where light penetrates.

Low tide

High tide

Intertidal zone



Benthic zone

Photic zone



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Section 6.2 Coastal and Marine Ecosystems

ecosystems that play an important role in the life cycle of many fish and marine organisms.
The rivers that flow into estuaries carry nutrients and sediment from upstream, and these
create perfect conditions for salt-tolerant plant growth. The dense plant growth found in salt
marshes provides important habitat for birds, crabs, shrimp, clams, and oysters, and it also
serves as spawning grounds for many species of open ocean fish. In addition, salt marshes
(like freshwater wetlands) help filter pollution from the water, and they play an important
role in stabilizing coastal shorelines against storm surges. Unfortunately, estuaries and salt
marshes have been heavily affected by coastal property development, the construction of
shipping channels, and oil and gas operations, leaving some coastal areas more vulnerable
than before to flooding.

Mangrove Forests
In tropical and subtropical regions, mangrove forests are a more common feature in estuar-
ies than salt marshes. Mangroves are a variety of tree that can grow in brackish, or slightly
salty, water found in estuaries. Mangrove roots grow both upward out of the water to absorb
oxygen and downward to support the tree in the sediment below the surface of the water. Like
salt marshes, mangrove forests are highly productive ecosystems that support a vast array of
birds, fish, shellfish, and other organisms. The dense and tangled root systems of mangrove
forests provide safe spaces for juvenile fish to spawn and grow before moving to the open

Mangrove forests are also important for stabilizing coastal shorelines and absorbing heavy
waves and floodwaters. After a massive tsunami struck southern Asia and killed over 200,000
people in 2004, research showed that coastal areas with healthy and intact mangrove for-
ests experienced less severe destruction than those areas where mangrove forests did not
exist or had been cleared (Kinver, 2005). Unfortunately, over half of the world’s mangrove
forests have already been destroyed to make way for fish farming and aquaculture, coastal
development, or firewood and timber. In areas where mangrove forests have been cleared,
coastal areas are at increased risk of flooding, and nearby fisheries have seen declines in

Photodisc/DigitalVision/Getty Images aiisha5/iStock /Getty Images Plus

Estuaries (left) and mangrove forests (right) are two critical ecosystems in the intertidal zone.

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Section 6.2 Coastal and Marine Ecosystems

Benthic Zone
The benthic zone refers to the region at the bottom or lowest level of a body of water. The
ocean benthic zone extends all the way from the shallow sands of the intertidal zone, less than
a meter below the surface, to the deepest ocean trenches of the Pacific Ocean, 11,000 meters
(36,200 feet, or almost 7 miles) deep. The most productive regions of the benthic zone are
found in relatively shallow waters where light is available. And among the most important
ecosystems found in this shallow portion of the benthic zone are seagrass beds, kelp forests,
and coral reefs.

Seagrass Beds
Seagrasses are underwater plants adapted to submersion in salt water. Large areas of sea-
grass, or seagrass beds, grow up to 10 meters (32 feet) below the surface, where there is
still enough light for them to photosynthesize. Common seagrass varieties include eelgrass,
manatee grass, turtle grass, and shoal grass. Seagrass beds help stabilize coastal ecosystems,
absorb wave energy, and reduce erosion. They are also an important habitat and food source
for shorebirds, sea turtles, manatees, and a variety of fish that “graze” on the seagrass in the
same way that a land-based animal might graze on prairie grasses.

Kelp Forests
Kelp is a type of brown algae or seaweed that can grow in dense stands known as kelp forests.
Kelp is more commonly found in cooler, shallow waters and along rocky coastal areas. Kelp
grows from the floor of the ocean in long strands toward the surface, with some kelp reaching
up to 60 meters (200 feet) in length. The dense vegetation found in kelp forests helps absorb
wave energy and reduce coastal erosion. This vegetation also provides a perfect habitat and
food source for many varieties of fish, shellfish, crustaceans, and other organisms.

richcarey/iStock/Getty Images Plus Windzepher/iStock/Getty Images Plus

Seagrass beds and kelp forests are two productive ecosystems where sunlight reaches the
benthic zone.

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Section 6.2 Coastal and Marine Ecosystems

Coral Reefs
Corals are small invertebrates (animals lacking a backbone) that are related to jellyfish and
sea anemones. Corals attach themselves to rocks or other underwater surfaces and build a
limestone shell around themselves for protection, using minerals available in the water.

Corals feed in one of two ways. First, they live in a symbiotic relationship with algae known
as zooxanthellae that inhabit their tissues and produce food through photosynthesis. It is the
different varieties of zooxanthellae algae that give corals their brilliant colors. Second, corals
use tiny stinging tentacles to paralyze plankton and other small organisms that drift by and
feed on the plankton. As corals die, the tiny shells they built for themselves remain, and a
new generation of corals builds on top of these. Over time, these accumulated layers of lime-
stone shells form entire reefs that are home to coral colonies containing millions of individual

Like kelp forests, seagrass beds, and mangrove forests, the physical structures of coral reefs
absorb wave energy and help reduce coastal erosion and flooding. Coral reefs are also the
most biodiverse of all marine ecosystems, equivalent in some ways to the tropical rain forests
on land. Coral reefs are home to hundreds of fish species and other organisms, and they are a
critical habitat and place of protection for juvenile fish. In addition, coral reef ecosystems are
an important contributor to local tourism in many regions.

Despite providing all these ecosystem functions and services, coral reefs are under threat
worldwide from a number of human-induced factors. Destructive fishing practices, including
the use of cyanide and dynamite to stun or blast fish out of the water, are destroying coral
reefs in some regions of Southeast Asia. Ocean pollution smothers coral reefs. And perhaps
of most concern, warmer ocean waters caused by global climate change are leading to coral
bleaching and the large-scale die-off of corals around the world. These and other causes of
coral reef decline will be discussed further later in the chapter.

Learn More: Kelp Forests

This short video allows you to take a virtual dive through a kelp forest off of the California

• https://www.calacademy.org/educators/take-a-virtual-dive-in-a-kelp-forest

In recent years marine scientists have uncovered interesting connections between the health
of kelp forests and populations of sea urchins and sea otters. Warmer ocean waters have led
to rapid growth in the populations of sea urchins, and these creatures love to graze on kelp. In
some areas kelp forests have been grazed to almost nothing by rising numbers of sea urchins,
a type of underwater deforestation. However, recall from Chapter 2 that sea otters prey on
sea urchins, and in places where healthy populations of sea otters exist, the kelp forests are
in better condition. This relationship between the health of the kelp forests and the status of
the sea otter population is one reason why otters are considered a keystone species in these

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Section 6.2 Coastal and Marine Ecosystems

Pelagic Zone
The pelagic zone refers to everything else in the ocean that is not a part of the intertidal or
benthic zones; namely, all the oceans’ open waters. The vast expanse of the pelagic zone is
usually further subdivided into horizontal zones by depth and degree of light penetration,
because light and nutrient availability are the key determinants of biological productivity
in these waters. Generally, the upper 200 meters (650 feet) of the ocean is classified as the
photic zone because light from the sun can reach that level. Everything below 200 meters
in depth, fully 94% of all ocean water, is classified as the aphotic zone because it is usually
beyond the reach of light from the surface.

Phytoplankton found in the pelagic zone of the world’s oceans are the most important pro-
ducers of the sea, and most primary production in the oceans occurs in regions favorable to
the growth of phytoplankton. Because producers like phytoplankton need sunlight to photo-
synthesize, virtually all primary production occurs in the photic zone. In addition, because
phytoplankton, like other plants and algae, need nutrients, primary production is even higher
in the photic zone near upwelling currents and estuaries that receive a steady input of nutri-
ents. Overall, this means that biological productivity and diversity in the pelagic zone is highly
variable across oceans, depending on location and light and nutrient levels. And because phy-
toplankton form the base of the marine food web, their abundance in surface waters near
upwelling currents and estuaries means that most marine life will be located there as well.

Below the photic zone, in the vast depths of the ocean aphotic zone known as the oceanic
province or the deep sea, living conditions become more extreme, and life forms can become
bizarre. Environmental conditions in these waters include extremely high pressures, a com-
plete absence of light, low oxygen levels, and very cold water temperatures. Despite these
extremes, an array of life has evolved and adapted to survive in these conditions. Most aquatic
life in the deep sea relies on marine snow for food and energy. Other organisms have adapted
to living around hydrothermal vents on the ocean floor that pump out mineral-rich heated
water from below the surface.

Some of the strangest and most remarkable creatures in the ocean make the deep sea their
home. This includes spider crabs that can span over 5 meters (16 feet) from claw to claw
and weigh up to 19 kilograms (42 pounds), deep sea dragonfish and anglerfish that produce
their own light to lure prey toward them, and sea creatures with names that fit their bizarre
appearance: the Pacific viperfish, the fangtooth fish, the Atlantic wolffish, the terrible-claw
lobster, the goblin shark, the vampire squid, and the colossal squid.

Reviewing Marine Ecosystem Functions and Services
Oceans are essential to human survival. As discussed earlier in this chapter, from 50% to
85% of the oxygen in the atmosphere is produced by marine phytoplankton. Oceans provide
up to 40% of the precipitation to land surfaces. Without ocean currents, the global climate
would be one of extremes. Most midlatitude and upper latitude regions, including much of the
United States, would be frigid and uninhabitable, and most places near the equator would be
too hot for human settlement. Marine ecosystems like coral reefs, kelp forests, salt marshes,
seagrass beds, and mangrove forests reduce wave energy, slow erosion and flooding, remove
pollutants from the water, and cycle nutrients.

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Section 6.3 Ocean Pollution

One ecosystem service we have yet to discuss has to do with the role of phytoplankton in
the carbon cycle. When phytoplankton photosynthesize, they absorb carbon dioxide from the
atmosphere. As phytoplankton die or get eaten by other organisms, that carbon gets trans-
ported to the deep sea as part of marine snow, and some of that carbon ends up becoming
part of deep sea marine sediments, where it is stored for centuries. In this way oceans act as a
biological pump that transfers some carbon dioxide (a greenhouse gas that can contribute to
global warming) from the atmosphere to the bottom of the ocean.

Beyond these environmental functions and services, ocean and marine ecosystems generate
a range of direct economic benefits. For starters, commercial fisheries employ tens of millions
of people worldwide and generate hundreds of billions of dollars in revenue each year. Like-
wise, coastal and marine tourism is a major industry in many countries, employing a similar
number of people and generating even more revenue than commercial fisheries. The world’s
oceans provide convenient shipping lanes for global commerce and transportation. And the
oceans are also an increasingly important source of pharmaceutical products and compounds
that can treat illness and disease. Interest in marine sources of medicinal products has led to
the establishment of an entire field known as marine pharmacology.

While it’s challenging to find the precise economic value of the oceans’ products and services,
in 2015 the World Wide Fund for Nature attempted to do just that. The group’s research sug-
gests that a conservative estimate of the “asset value” of the world’s oceans is $24 trillion and
that these assets yield goods and services to humans with a value of at least $2.5 trillion every
year (World Wide Fund for Nature, 2015). Much of these goods and services take the form
of seafood harvests, tourism revenue, the value of shipping lanes, and erosion prevention
provided by coastal ecosystems. In other words, this $2.5 trillion estimate does not include
environmental services: oxygen production, water cycling, and climate regulation.

The remainder of this chapter will review some of the major ways we are threatening or
destroying these ecosystems that are so critical to our economy and well-being—and some of
the steps being taken to mitigate that destruction.

6.3 Ocean Pollution

Perhaps because oceans seem far away and out of sight, we engage in many activities that
harm the health of the oceans and destroy critical marine ecosystems. This section will review
the most basic threat: pollution. Given that there are so many different ways we pollute the
ocean, the discussion is broken down into issues of nutrient pollution, plastic pollution, oil
spill pollution, and other forms of ocean pollution.

Nutrient Pollution
Nutrient pollution refers to the impact of excess nutrients on marine ecosystems, which we
have discussed to some extent in previous chapters. When fertilizers run off of farm fields, golf
courses, and suburban lawns, or when nutrient-rich animal waste flows into nearby streams
and rivers from animal feeding operations, large quantities of nitrogen and phosphorous are

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Section 6.3 Ocean Pollution

introduced to these ecosystems. This eutro-
phication leads to rapid growth of phyto-
plankton and potentially sudden drops in
dissolved oxygen levels, a condition known
as hypoxia. Hypoxia or hypoxic conditions
can lead to the death and displacement of
a wide variety of marine life and result in
what is known as an aquatic dead zone, as
discussed in the case study in Chapter 2.

A specific type of algal bloom that can be
very destructive and dangerous to marine
life and even humans is commonly known
as a “red tide.” Red tides are caused by an
explosion of growth in a specific type of
algae known as dinoflagellates, and when
millions of these algae grow in a specific
location, they can change the color of the
water to red, pink, orange, or yellow. Dinoflagellates contain a toxin that can affect the ner-
vous systems of marine animals, which is why marine scientists prefer to call these outbreaks
harmful algal blooms, or HABs. In 2018 massive HABs broke out along Florida’s Gulf coast,
resulting in the death of hundreds of sea turtles, manatees, and dolphins, as well as tens of
thousands of fish. As dead fish and marine mammals washed up onshore, the neurotoxin that
caused their deaths had the potential to become airborne and sicken people. As a result, long
stretches of beach were closed, and the state lost billions of dollars in tourism revenue. While
HABs do occur naturally, they become more frequent and large scale because of nutrient pol-
lution from human activities.

The frequency and intensity of eutrophication, dead zones, and harmful algal blooms can be
reduced in a number of ways. The key is to reduce the rate of nutrient pollution that reaches
the ocean. More careful application of fertilizers to farm fields, golf courses, and suburban
lawns will reduce nitrogen and phosphorus runoff. Farmers could also make greater use of
riparian buffers that absorb nutrients before they can enter streams and rivers. Likewise,
better management of waste products from animal feeding operations can reduce nutrient
runoff from this source. Farther downstream, restoration and protection of coastal wetlands
and salt marshes can go a long way toward reducing nutrient pollution of the oceans, since
these ecosystems soak up excess nutrients from the waters that pass through them. Lastly,
some areas are turning to shellfish like oysters and mussels to reduce nutrient pollution of
nearby waters. For example, an effort known as the Billion Oyster Project is restoring oyster
populations to the polluted waters of New York Harbor. Oysters filter up to 190 liters (50
gallons) of water a day, and this project aims to establish enough oyster beds to filter all the
water in New York Harbor every few days.

Plastic Pollution
Plastic pollution is a relatively new problem. Plastics did not come into widespread produc-
tion and use until after World War II, but today they are seemingly everywhere and a part of
almost every product we use in our everyday lives. Plastics are light, inexpensive and easy

Justin Smith/iStock/Getty Images Plus
Algae bloom in a wetland area, which has
caused the water to look red and murky. These
sorts of harmful algal blooms (HABs) are
harmful to both marine and human life.

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Section 6.3 Ocean Pollution

to produce, and convenient for manufacturers and consumers alike. However, some of those
same benefits are now contributing to making plastics a major pollution problem on land, in
the sea, and in just about every region of the world.

Researchers estimate that in the past 60 to 70 years, 8.3 billion metric tons of plastics have
been produced globally (see Figure 6.4). Of that total, roughly 5 billion metric tons has either
been sent to landfills or is still located somewhere else in the environment (Geyer, Jambeck,
& Law, 2017). From this plastic waste, it’s estimated that roughly 8 million metric tons enters
the oceans from land surfaces each year (Jambeck et al., 2015).

Figure 6.4: Global plastic production

Global plastic production and use exploded after World War II.

Source: Adapted from “FAQs on Plastics,” by H. Ritchie, 2018 (https://ourworldindata.org/faq-on-plastics). CC BY.


















1960 1970 1980 20151990 2000 2010

And the problem of plastic pollution is not going to go away anytime soon. We are still pro-
ducing an estimated 310 million metric tons of plastic every year, with roughly 82 million
metric tons going to plastic packaging alone. Most plastic packaging is designed specifically
for a single use and then disposal, with limited or no options for recycling or reuse, so much
of this plastic will continue to enter landfills or the environment. The most common single-
use items made of plastic that are found during ocean and beach cleanups are cigarette butts
(which contain a small plastic filter), food wrappers, beverage bottles, bottle caps, grocery
bags, straws, lids, and take-out boxes. We produce over 6 trillion cigarettes and 5 trillion plas-
tic grocery bags every year.

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Section 6.3 Ocean Pollution

Impact on Marine and Human Life
Plastic pollution is such a serious problem because plastic wastes do not biodegrade in the
same way that organic wastes do. Instead, they undergo a process known as photodegrada-
tion, in which materials are broken down into smaller pieces by sunlight. Because plastic that
is in the water is not as directly exposed to sunlight, plastic waste in the oceans and other
bodies of water photodegrades more slowly than on land, taking as long as 500 to 1,000 years
to fully break down. To make matters worse, since plastics do break down into smaller pieces,
they are mistaken as food by fish and marine mammals. And because most plastic is made
using toxic materials, these toxins also become part of what is ingested.

The National Oceanic and Atmospheric Administration has identified three main ways in
which ocean plastic pollution is impacting marine life. First, ocean plastic pollution often con-
sists of plastic fishing nets, ropes, and other debris from fishing fleets. Marine life, especially
mammals like sea turtles, whales, and dolphins, can become entangled in this debris and
either suffocate or drown.

Second, marine animals often mistake plastic pollution for food and ingest it. This plastic
waste can accumulate in their stomachs and create intestinal blockages and other problems.
A recent study by Australian scientists found that over half of all sea turtles around the world
have ingested plastic debris and that just a small amount of ingested plastic can significantly
increase the risk of death for these creatures (Weintraub, 2018). To make matters worse, the
toxins used to make most plastic thereby enter the food chain and can amass in the tissues
of marine life higher up on the food chain. For example, Styrofoam products contain carcino-
genic chemicals like styrene and benzene. Scientists are now referring to the trillions of tiny
pieces of plastic building up in oceans, rivers, lakes, and streams as microplastics, and they
are worried that these microplastics are so pervasive that they might now threaten human
health. This is because we could be ingesting this material when we eat fish and even when
we drink water drawn from surface waters. (The Close to Home feature box explores one type
of microplastic found in clothing.)

Third, some species can use plastic debris and ocean currents to move from one place to the
other, and this can introduce nonnative invasive species to new ecosystems. Overall, the UN
estimates that plastic pollution of the world’s oceans imposes economic costs of at least $13
billion every year, including cleanup costs and lost tourism revenue (United Nations Environ-
ment Programme, 2014).

Ian Dyball/iStock/Getty Images Plus Erlantz Pérez Rodríguez/iStock/Getty Images Plus

Pollution is devastating to marine life. They can become entangled, as this seal (left), or they
might ingest some of the trillions of microplastics (right).

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Section 6.3 Ocean Pollution

Close to Home: Examining Choices Around Clothing

You might be surprised to learn that some forms of microplastic pollution come from the
clothing we wear on a daily basis. These plastic microfibers represent a new frontier in
environmental research, and recent findings suggest that they make up a significant fraction
of ocean plastic pollution.

Clothing materials come in a variety of forms.
Natural fibers like wool, linen, and cotton
come from plants and animals, and unless they
are treated with harsh chemicals, they do not
usually pose a major environmental concern
when released into the environment. Over
the past several decades, however, human-
made fabrics have become far more common.
Petroleum-based synthetic fibers like polyester,
spandex, and nylon now make up about 60% of
clothing worldwide (Resnick, 2019).

Like most clothing materials, synthetic fabrics
wear out over time. As they age, fibers begin
to fray and break off into smaller pieces called
microfibers. When people wash their clothing,
these plastic particles are shed in large quantities into the washing machine’s wastewater,
and the particles are too small to be captured by most sewage treatment facilities. Many
microfibers find their way into rivers and oceans that transport them all over the world.
Researchers have found microfibers throughout rivers, lakes, and oceans; in the sand on
remote islands; in the air; and even inside the fish and shellfish that we eat. Because salt
water is sometimes used to make salt, microfibers can be found there too, and because
treated sewage is sometimes used as fertilizer, microfibers can be found in our soil. Plastic
microfibers are pretty much everywhere!

Unlike natural fibers, plastic microfibers do not break down very easily in the environment,
and some animals mistake them for food. Consuming microfibers can result in nutritional
deficiencies, digestive problems, and even death for smaller creatures like zooplankton,
shellfish, and earthworms. Microfibers can also transmit toxins into the soft tissue of larger
organisms like fish, seabirds, and filter-feeding whales. Many of the risks associated with
microfiber pollution are still unknown, but the more we learn, the more cause we have to be

Take a look at a few of your clothing tags and see if your wardrobe is a source of microfiber
pollution. If you find materials like nylon, polyester, spandex, acrylic, and acetate, take a
moment to develop some strategies for reducing your individual microfiber emissions. Are
there lifestyle choices you could make to reduce microfiber pollution and still live a happy
and healthy life? Are there more environmentally friendly choices that you can make as a
consumer? Are there more technological or systemic solutions that might be outside of your
immediate control? What kinds of actions do you think will be most effective when tackling
this environmental challenge?

If you don’t have all the answers, you are not alone. The plastic microfiber problem is new to
most researchers, engineers, and city planners. We are only just beginning to understand the
possible impacts of this form of plastic pollution, and we need creative minds to develop new

Nylon microfiber viewed under a

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Section 6.3 Ocean Pollution

Plastic pollution in the oceans tends to get concentrated in certain areas because of the circu-
lar flow of water caused by gyres. This whirlpool effect has concentrated volumes of plastic
debris and waste into what are known as “garbage patches.” The most well known of these
garbage patches has come to be called the Great Pacific Garbage Patch (GPGP).

In reality, the GPGP refers to two separate garbage patches in the North Pacific Ocean, one
near Japan in the western Pacific and the other between Hawaii and California in the eastern
Pacific. The eastern portion of the GPGP was recently the subject of a scientific expedition that
set out to determine the volume, scope, and composition of the plastic pollution found there.
This research found that the eastern part of the GPGP extended across an area of ocean 1.6
million square kilometers (617,763 square miles) in size, an area twice the size of Texas. It
also estimated that there were over 1.8 trillion pieces of plastic in the garbage patch, with a
total weight of 80,000 metric tons. In terms of the number of pieces, most of this plastic waste
was in the form of microplastics smaller than 5 millimeters in size (roughly the size of a letter
on a keyboard). However, when measured by weight, 46% of the garbage patch consisted of
discarded fishing nets and other gear (Ocean Cleanup, n.d.).

Learn More: An Island of Plastic Waste

In May 2019 a group of Australian marine scientists led by research scientist Jennifer Lavers
published the results of a study they conducted on plastic pollution in the Cocos Islands of
Australia. The Cocos Islands are located in the remote Indian Ocean, far off the northwestern
coast of Australia and far from any commercial or population centers. The islands are billed
as Australia’s “last unspoilt paradise” (Cocos Keeling Islands, 2019, para. 1), and so it came
as a surprise when the researchers discovered hundreds of millions of pieces of plastic waste
on the beaches of Cocos. The final tally of plastic waste from their survey was staggering:
373,000 plastic toothbrushes, 975,000 plastic flip-flops, and an estimated 414 million pieces
of plastic waste weighing a total of 238 metric tons. Equally amazing was that the plastic
waste was not just on the surface of the beach but got thicker as the scientists dug deeper.
You can learn more about this research and what it tells us about plastic pollution, ocean
currents, and its impact on marine biodiversity and wildlife by visiting these links:

• https://www.nature.com/articles/s41598-019-43375-4
• https://natureecoevocommunity.nature.com/users/262039-jennifer-lavers


• https://www.youtube.com/watch?v=f TGmpVUXwF4

Efforts to Reduce Plastic Pollution
Given that plastic pollution of the world’s oceans is now being measured in billions of pounds
and trillions of pieces, it would seem like an impossible task to try to clean it up. However,
that did not stop a young inventor named Boyan Slat, who in 2012 first proposed the idea of a
floating device to collect plastic waste from the oceans. Slat went on to form an organization
known as Ocean Cleanup, which raised millions of dollars to develop and test a 600-meter-
long (2,000-foot-long) buoy device to “sweep the sea” of plastic debris. Unfortunately, early

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Section 6.3 Ocean Pollution

tests of this device that occurred in areas of the GPGP in late 2018 resulted in a complete
failure. Rough seas and mechanical problems prevented the sea sweeper from collecting any
measurable plastic waste, and the device is currently undergoing modifications for further

Even before the initial failure of the sea sweeper project, most marine scientists agreed that
ocean plastic pollution could realistically only be addressed through prevention. This includes
managing plastic waste on land to prevent it from ever reaching the oceans in the first place,
as well as improving plastic recycling, designing more plastic products to be reused, using
more biodegradable plastics, and substituting nonplastic packaging material. Even outright
bans on some types of plastic material—especially single-use packaging, bags, and straws—
are becoming more common.

Oil Spill Pollution
On April 20, 2010, there was a massive
explosion on the Deepwater Horizon oil
platform in the Gulf of Mexico, 68 kilome-
ters (42 miles) off the coast of Louisiana.
The explosion killed 11 workers and ripped
open underwater piping, which began pour-
ing thousands of gallons of oil into the Gulf.
It took almost 3 months to cap the pipe and
control the flow of oil, and by that time an
estimated 3.2 million barrels (134 million
gallons) of oil had leaked into the Gulf. As
a result, hundreds of thousands of seabirds
died, the Gulf shrimp fishery closed, over
1,600 kilometers (almost 1,000 miles) of
beach from Texas to Florida were fouled
with oil slicks, and fish and marine mammal
deaths increased. The longer term impacts
of the oil spill are more difficult to determine. Recent studies have shown that oil residues
from the spill are still altering deep sea life in the area around the site of the disaster (Girard
& Fisher, 2018; Biedron & Evans, 2016). Other research is ongoing to determine both the fate
and effects of the spilled oil and to see if any of the chemical dispersants used to clean up the
spill are having harmful impacts on wildlife and ecosystems in the Gulf.

Twenty-one years before the Deepwater Horizon oil spill in the Gulf of Mexico, the Exxon Val-
dez oil tanker ran aground in Prince William Sound in Alaska. At the time, the Exxon Valdez oil
spill was the worst of its kind in the United States, and it had devastating impacts on wildlife,
commercial fisheries, and native Alaskan communities in the area. Other large oil spills from
oil platform disasters or tanker accidents have also had devastating impacts on marine life,
commercial fisheries, and coastal tourism. Fortunately, the number of major oil spills from oil
tankers has been going down over the years, due to improved safety features and designs. The
biggest impact has come from the shift to double-hull tankers that have an outer and inner
plate separating oil from the water.

Coast Guard Public/SuperStock
The Deepwater Horizon oil platform explosion
resulted in an estimated 3.2 million barrels of
oil spilling into the Gulf of Mexico.

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Section 6.3 Ocean Pollution

While oil spill pollution from oil tanker disasters is on the decline, it turns out that these
disasters are not even the largest source of oil pollution in the world’s oceans. Instead, the
greatest amount of oil pollution comes from routine, and often intentional, dumping of
smaller amounts of oil into the water. Thousands of commercial ships and even larger num-
bers of small recreational craft constantly leak oil into the ocean. Likewise, millions of cars
and trucks on land are constantly leaking oil that can run off of road and parking lot surfaces
and make its way to the sea. In addition, some individuals dump motor oil from oil changes
into storm drains, and this oil is washed into nearby bodies of water and to the sea. All these
small inputs of oil add up and can have more subtle but still significant impacts on wildlife
relative to the major oil spills that receive most of our attention.

A final area of concern regarding oil spills involves pipelines that run under or near bodies of
water. For example, the Trans Mountain oil pipeline in Canada carries crude oil from tar sand
deposits in Alberta to a port area in British Columbia, 1,150 kilometers (715 miles) away.
There the crude oil is refined and shipped to China and other oil-importing nations in Asia.
A proposed expansion of this pipeline has resulted in fierce opposition from environmental
groups, commercial fishing organizations, and First Nation tribes. The waters and shorelines
around the Trans Mountain marine terminal are critical areas of habitat for a variety of whale
species, chinook salmon, and Pacific herring, as well as nesting and breeding grounds for mil-
lions of seabirds. A pipeline rupture or oil tanker accident and spill in or near these habitats
could have devastating effects. For now, however, the Canadian government is promising to
move ahead with the proposed expansion of the pipeline while ensuring that safeguards will
be put in place to minimize the impact of any oil spill disaster.

Other Forms of Marine Pollution
There are other forms of ocean and marine pollution that get less attention but are important
to consider.

Noise Pollution
While being underwater may seem quiet to our ears, the issue of ocean noise pollution has
gained increasing attention from marine scientists in recent years. Because whales, dolphins,
fish, and other marine life use sound to communicate, find food, and navigate, human activi-
ties that create underwater noise can be highly disruptive to these creatures.

Among the major causes of ocean noise pollution are commercial ship traffic, high-intensity
sonar, and high-powered underwater air guns used for offshore oil and gas exploration. There
are roughly 60,000 commercial oil tankers and container ships that ply the world’s oceans
and waterways every day, creating underwater noise with their propellers—another reason
opponents are concerned about the Trans Mountain oil pipeline expansion. Likewise, the U.S.
Navy and other major power navies use high-intensity sonar to navigate and to detect under-
water objects such as submarines. The sound waves created by high-intensity sonar have
been shown to drive whales and other marine mammals away from an area (Parsons, 2017;
Bernaldo de Quirós et al., 2019). In some cases the noise pollution created by high-intensity
sonar has been so bad that large numbers of whales and dolphins have beached themselves
and ended up dying to get away from the sounds.

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Section 6.3 Ocean Pollution

However, it is the growing use of high-powered underwater air guns or seismic air guns that
has been getting the most attention in recent years. Air guns are used on giant ships that criss-
cross ocean waters in a grid pattern for oil and gas exploration. A single ship might be mounted
with up to 48 air guns, with each gun blasting pressurized air into the water beneath it every
10 to 12 seconds for weeks or months at a time. The sound waves from the air blasts bounce off
the ocean floor and back to the surface, where other equipment on the ship records them and
uses this information to create maps of where oil and gas might be located. The sound from
air guns can reach up to 260 decibels underwater, equivalent to 200 decibels aboveground. By
comparison, the launch of the Space Shuttle created a sound of about 160 decibels for people
nearby. The sound from air gun blasts can also travel long distances, as much as 4,000 kilome-
ters (2,500 miles) in some cases. Overall, marine scientists have described the sheer intensity,
frequency, and range of noise pollution from seismic air guns as creating a “living hell” for
underwater marine life (Robbins, 2019). Recent research has even revealed that blasts from
seismic air guns can kill large numbers of tiny zooplankton near the base of many marine food
webs (McCauley et al., 2017; Tibbetts, 2018). In addition, research conducted in Norway found
that commercial fish catches decline by up to 80% in areas where seismic air guns are being
used for oil and gas exploration (Huelsenbeck & Wood, 2013).

Atmospheric Deposition
Another invisible form of ocean pollution actually starts out as air pollution. Industrial activi-
ties and energy consumption (such as burning coal) can put heavy metals and toxins like
mercury and lead into the atmosphere. These air pollutants are carried by winds over oceans
and other bodies of water, where they can wash out and fall to the surface when it rains. Such
atmospheric deposition of heavy metals and other pollutants can have slow-moving and
almost imperceptible impacts on marine food webs and eventually even affect human health.

Toxins like mercury and lead can be absorbed by phytoplankton and zooplankton, which form
the base of many marine food webs. When larger marine animals consume large quantities of
these plankton, they ingest more of the toxins, and when even larger marine animals consume
those marine animals, the concentrations of toxins can increase even further. Recall that this
increasing concentration of toxins at higher levels of the food chain is known as biomagnifica-
tion (see Chapter 4). Bioaccumulation refers to the buildup of toxins in an individual organ-
ism over time. Because of biomagnification and bioaccumulation, levels of mercury and other
toxins in some species of fish near the top of the food chain are so high that they pose a health
risk to humans.

Finally, a somewhat novel form of ocean pollution is sunscreen. In early February 2019 the
City Commission of Key West, Florida, voted 6–1 to ban sales of sunscreen that contain chemi-
cals (mainly oxybenzone and octinoxate) believed to be harmful to coral reefs. Key West joins
the state of Hawaii and the small country of Palau in banning sales of certain types of sun-
screen, which can wash off of swimmers and snorkelers and come in contact with coral reefs.
The chemicals lead to bleaching and other damage to the corals. Marine scientists and envi-
ronmental groups concerned about this issue point to “coral safe sunscreens,” which do not
contain these harmful chemicals, and encourage people to use these instead.

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Section 6.4 Other Major Threats to Ocean and Marine Ecosystems

6.4 Other Major Threats to Ocean and Marine Ecosystems

Besides the direct impact on marine ecosystems of various forms of pollution, there are a
number of indirect threats to our oceans that we need to consider. We’ll start with the physi-
cal and chemical changes to oceans and marine ecosystems due to climate change. This is fol-
lowed by an examination of the problem of overfishing and the ripple effects this has through-
out marine food webs. Lastly, we’ll consider issues of marine and coastal habitat destruction
and invasive species.

Climate Change
Over the past 200 years, as human use of fossil fuels like oil, coal, and natural gas has increased,
so too have atmospheric concentrations of carbon dioxide. The combustion of fossil fuels
releases CO2 to the atmosphere, and as a result atmospheric concentrations of this gas have
risen from 280 ppm around the year 1800 to over 400 ppm today.

Because CO2 is a greenhouse gas, increased atmospheric concentrations have resulted in
warming of the planet, something we will explore in much more detail in Chapter 8. This
global warming has also resulted in warming of the oceans, which is negatively affecting
marine life and biodiversity. In addition, higher atmospheric concentrations of CO2 are actu-
ally changing the chemistry of ocean waters, with equally serious impacts. This twin threat to
oceans from rising CO2 levels is the subject of this section.

Ocean Warming
Greenhouse gases like carbon dioxide and methane trap and hold heat in the Earth’s atmo-
sphere. The increase in atmospheric concentrations of CO2 and other greenhouse gases since
the start of the Industrial Revolution has already resulted in warming of the planet’s surface
by roughly 1 degree Celsius (about 1.8 degrees Fahrenheit). But it turns out that this surface
warming would be much worse were it not for the fact that the oceans have been absorbing

Learn More: Are Coral Safe Sunscreens for Real?

Recent efforts to ban the sale of sunscreens that contain oxybenzone and octinoxate have led
to the development and marketing of what are being labeled as “coral safe” and “ocean safe”
versions. While this is a move in the right direction, a 2019 analysis by Consumer Reports
magazine found that even these supposedly eco-friendly sunscreens might still be harmful
to coral and other marine life. Consumer Reports recommends wearing UPF (ultraviolet
protection factor) clothing as a way to cut down on the amount of exposed skin that needs
to be treated with sunscreen. You can learn more about this issue and the findings of the
Consumer Reports research here:

• https://www.consumerreports.org/sunscreens/the-truth-about-reef-safe

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Section 6.4 Other Major Threats to Ocean and Marine Ecosystems

over 90% of the additional heat caused by human greenhouse gas emissions. While this
absorption has helped slow the rate of global warming, it is having profound and destructive
effects on the world’s oceans. Each year the oceans become warmer than the year before: As
of this writing, 2018 was the warmest year on record for the world’s oceans; 2019 data was
not yet available. Warmer oceans mean increased sea level rise and coastal flooding, as well
as more powerful hurricanes and coastal storms.

Warmer ocean waters can also be very destructive to coral reef ecosystems. Recall that cor-
als are actually tiny invertebrate animals that attach themselves to underwater surfaces and
build a calcium carbonate shell for protection. Also recall that these coral animals live in a
symbiotic relationship with colorful algae known as zooxanthellae. The zooxanthellae can
produce food through photosynthesis and share some of that food with the coral animals
that give them a home. Marine scientists now know that warmer ocean waters cause coral
animals to expel the zooxanthellae algae, resulting in coral bleaching. Coral bleaching is so
named because of the whitening that occurs due to the loss of the vibrant zooxanthellae, but
it’s not just about color. The photosynthetic actions of the zooxanthellae algae provide cor-
als with as much as 90% of their energy needs, and when they are expelled the corals can
weaken and die.

Recent assessments of Australia’s Great Barrier Reef—the largest coral reef ecosystem in the
world—have determined that 90% of corals there show evidence of bleaching (Kahn, 2016).
Marine scientists who study the Great Barrier Reef are now predicting a massive coral die-
off and planetary catastrophe. In other parts of the world, there is evidence that even if coral
bleaching doesn’t kill coral organisms outright, it weakens them and lowers their ability to
fight off disease. As much as 80% of corals in the Caribbean, weakened by coral bleaching,
have been wiped out from “white band disease,” and a number of important coral species are
nearing extinction.

Moodboard/Thinkstock Gerald Nowak/Westend61/SuperStock

Warming ocean temperatures are detrimental to coral reefs across the globe. Here two photos
show different coral reefs in Indonesia. One reef is thriving (left), while the other is now dead

Ocean Acidification
Corals and a variety of other marine organisms are also being negatively affected by a prob-
lem known as ocean acidification, whereby the ocean becomes overly acidic because of too
much CO2.

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Section 6.4 Other Major Threats to Ocean and Marine Ecosystems

Recall that an important ecosystem service provided by oceans is that they act like a biologi-
cal pump, taking excess carbon dioxide from the atmosphere and transferring it to sediments
at the bottom of the ocean. Scientists now estimate that the oceans are absorbing as much as
one third of excess CO2 emissions from fossil fuel combustion. While this seems like it would
be a good thing and would slow global warming, the absorption of too much CO2 actually
alters the basic chemistry of ocean waters.

When CO2 combines with ocean water, it produces carbonic acid (H2CO3), increasing the acid-
ity of the water. This process also reduces the level of carbonate ions in the water, and car-
bonate ions are used by marine organisms like corals, oysters, and even some types of phy-
toplankton to produce calcium carbonate for their shells. Lower levels of carbonate ions can
slow the rate of coral growth and weaken shells of marine organisms like oysters, mussels,
crabs, and sea snails.

Worldwide measurements of ocean chemistry show that oceans are warmer and more acidic
now than at any time in the past 400,000 years. While many marine organisms might be able
to adapt to slow-moving and slight changes in ocean temperature and chemistry, the rate of
change is currently too much for some to adjust to. The average acidity of the world’s oceans
has increased 30% since 1800, and this fundamental change in ocean chemistry is adding
to the stress caused by warming and pollution. There is even growing evidence that both
ocean warming and acidification are reducing populations of phytoplankton, which will in
turn affect the higher echelons of the marine food web (Smithsonian Ocean Portal, n.d.).

While the most obvious answer to ocean warming and acidification is to reduce combustion
of fossil fuels and CO2 emissions, scientists are also looking at other ways to deal with these
challenges. Marine scientists in the Pacific Northwest are looking at whether marine plants
like kelp and seagrass can keep the water from getting too acidic for oysters and other marine
organisms. Because these marine plants use CO2 when they photosynthesize, the hope is that
more of them will prevent CO2 from being converted to carbonic acid.

Likewise, marine scientists in Australia and Hawaii are scrambling to collect coral sperm from
coral reef organisms. Worried that coral bleaching and acidification will wipe out coral reef
ecosystems, these scientists are collecting the sperm and freezing it in coral sperm banks. The
frozen sperm could be used to repopulate coral reefs in the future if conditions improve, and
it is also being used to help breed “super corals” that can withstand warmer and more acidic
ocean waters.

Learn More: Coral Reefs

Coral reefs are truly amazing ecosystems. You can learn more about them and the threats to
them at these sites.

• https://ocean.si.edu/ecosystems/coral-reefs
• https://www.virtualreef.org.au
• https://oceanservice.noaa.gov/ocean/corals

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Section 6.4 Other Major Threats to Ocean and Marine Ecosystems

The Food and Agriculture Organization (FAO) of the United Nations (2018b) estimates that
fish accounts for about 17% of worldwide animal protein consumption. The FAO also esti-
mates that over 50 million people are employed in commercial fisheries around the world
and that the value of the commercial fish catch comes to over $360 billion annually.

Historically, most of the global fish catch came from what are known as “capture fisheries,”
which catch wild fish in the open water. However, beginning around the 1980s, global fish
catch from capture fisheries began to level off even as population growth and demand for fish
were increasing. Massive investments in aquaculture, or fish farming, began around that time,
and today aquaculture production comes close to the same levels as that of capture fisheries.
The latest statistics on production from the FAO are for 2016, when the total fish catch from
capture fisheries came to 90.9 million metric tons. In that same year, fish production from
aquaculture or commercial fish farming came to 80 million metric tons.

The leveling off of global fish catch from capture fisheries is not for lack of trying. It is sim-
ply because many commercial fisheries have been overfished for decades and are just not as
productive as they once were. An estimated 4.6 million commercial fishing boats work the
world’s oceans and inland waterways (FAO, 2018b). Many are equipped with high-tech GPS,
sonar, and other equipment to help them locate and catch wild fish. Some commercial fishing
fleets use spotter planes and drones to help them find wild fish stocks, as well as massive fac-
tory ships that process and freeze fish for months at a time out on the high seas.

The FAO defines individual fisheries as being underfished, fully fished, or overfished. Under-
fished means that fish catch from that fishery can increase and still be sustainable. Fully fished
(or maximally sustainably fished) means that current catches are biologically sustainable but
cannot be increased. And overfished means that current catches are biologically unsustain-
able and that fishery is in decline. In 1974 the FAO reported that 90% of global fisheries were
either underfished or fully fished—that is, within biologically sustainable levels—and only
10% were overfished. By 2018 the percentage of global fisheries that were overfished had
increased to over 33%, with another 58% being fully fished. Global production from capture
fisheries has remained steady only because commercial fishing fleets are exploiting more

remote fishing grounds, capturing smaller
fish, and targeting less desirable fish species
than before.

Commercial fishing boats use a variety of
techniques and equipment to catch fish, and
some of these can have negative and lasting
impacts on marine ecosystems. Some of the
most common approaches to commercial
fishing include bottom trawling, purse sein-
ing, and drift netting.

Bottom trawling involves dragging large,
weighted fishing nets across the ocean floor.
Bottom trawling is considered one of the
most destructive forms of fishing and has

taylanibrahim/iStock/Getty Images Plus
Bottom trawling, as shown in this photo, is one
of the worst forms of fishing due to the damage
done to the ocean floor.

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Section 6.4 Other Major Threats to Ocean and Marine Ecosystems

been compared to bulldozing the ocean floor. As the weighted nets are dragged along, they
destroy deepwater reefs and other structures that are important habitat to marine life.

Purse seining involves the deployment of large circular nets that are drawn tighter and tighter
to capture fish, while drift nets are long stretches of net that are laid out for miles. Both purse
seining and drift netting result in the problem of bycatch, the accidental capture and death
of nontarget species, including dolphins, sea turtles, and even seabirds. Researchers estimate
that global fishing operations result in as much as 38.5 million metric tons of bycatch each
year (Davies, Cripps, Nickson, & Porter, 2009).

Overfishing not only reduces commercial fishing output but also influences the composition
of marine food webs. It’s estimated that wild populations of large fish like tuna, marlin, and
swordfish have declined by as much as 90% since the 1950s (Myers & Worm, 2003). The
absence of these fish near the top of marine food chains has resulted in problems further
down the chain, including large-scale jellyfish population explosions. Overfishing can affect
food webs in the opposite direction as well when the capture of prey fish impacts larger fish
that feed on them. Although efforts are being made to better regulate commercial fishing
operations and reduce overfishing, these efforts are complicated by the fact that most of the
world’s ocean waters are considered “high seas” and beyond the jurisdiction of any single

Habitat Destruction
We have already discussed some forms of marine and coastal habitat destruction, such as
clearing of mangrove forests for fish farms, bottom trawling (bulldozing) of deepwater reefs,
and demolition of shallow coral reefs through dynamite and cyanide. But there are other
forms of habitat destruction as well. For example, over 60% of the world’s 7.7 billion peo-
ple live within 160 kilometers (100 miles) of the ocean, resulting in the heavy development
of many areas along and near the coast. This has led to the destruction of many important
coastal ecosystems like salt marshes, as well as increased runoff into critical coastal waters.
Likewise, sediment from coastal developments, agriculture, or deforestation can wash out to
sea and smother coral reef ecosystems.

Coastal and marine tourism can also cause damage. Tour boats in areas with coral reefs can
damage ecosystems through dropping anchors or leaking oil. And snorkelers and divers can
step on and damage fragile coral reefs, while others break pieces off for souvenirs.

Invasive Species
Marine invasive species are organisms that have been moved from their original ocean habi-
tat to a new one and have begun reproducing successfully. One common method by which
marine invasive species are carried from one location to another is through ship ballast water.
Ships store ballast water in the bottom of their hulls to make them more stable. If a ship takes
in ballast water in one location and empties it in another, it can pick up invasive species and
drop them somewhere else. For example, the European green crab is believed to have been
introduced to North America through ballast water. This crab is a voracious feeder and in

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Section 6.5 Sustainable Management of Ocean and Marine Ecosystems

some places has decimated local shellfish
populations. European green crabs are now
established on five continents and are out-
competing many local species.

Another way that marine invasive species
are introduced is through accidental or
deliberate release into the wild. For exam-
ple, lionfish are native to tropical waters
in the western Pacific, but they are now a
common resident off the East Coast of the
United States and in the Gulf of Mexico. It’s
believed that lionfish got into these waters
after escaping from outdoor aquariums in
Florida that were damaged or destroyed by
Hurricane Andrew in 1992.

Lionfish have been called the “vacuums of the sea” because they can consume thousands of
other fish every year. Lionfish are also prolific breeders, with a single female able to spawn
over 2 million eggs in one year. Because lionfish have no natural predators, and because they
are protected by poisonous spines, controlling their numbers poses a challenge. Lionfish
control efforts in Florida now include campaigns to get more people to capture and eat this
reportedly tasty fish.

6.5 Sustainable Management of Ocean and Marine

From pollution to climate change to overfishing to habitat destruction, there are many rea-
sons to be concerned about the future of our oceans. While these threats and challenges can
seem overwhelming, there are efforts being made to slow or even reverse some of the damage
we’ve done to ocean and marine ecosystems.

The word aquaculture sounds a lot like agriculture for a reason. Aquaculture is the cultiva-
tion of fish, shrimp, and other marine life in ponds, pens, cages, and other confined settings.
When done right, it can help meet global demand for fish and other seafood in ways that avoid
or minimize damage to marine ecosystems. However, aquaculture is not always done right,
and as a result there is some controversy over just how beneficial this approach actually is.

Global aquaculture production has increased dramatically over the past 30 years, from
roughly 16 million metric tons a year in 1990 to over 80 million metric tons a year today.
This growth in aquaculture production occurred as capture fisheries’ production was leveling
off, making up the difference needed to feed a growing human population. Most aquaculture

atese/iStock /Getty Images Plus
Lionfish are prolific breeders, consume
thousands of other fish every year, and have no
natural predators.

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Section 6.5 Sustainable Management of Ocean and Marine Ecosystems

production takes place in Asia, accounting for over 70 million of the 80 million metric tons
in total world production. China alone produces 50 million metric tons of global aquaculture
output (FAO, 2018b).

Because aquaculture does not require bottom trawling, purse seining, or drift netting, it
avoids the kinds of problems associated with marine habitat destruction and bycatch. Raising
fish in aquaculture systems also takes pressure off wild fish stocks, potentially allowing ocean
fisheries to replenish.

However, a number of environmental problems have raised concerns about aquaculture’s
sustainability. First, farm-raised fish can escape from their ponds, pens, or cages into nearby
waterways, where they pose a risk of becoming invasive species. For example, Asian carp have
escaped from aquaculture facilities and are now an invasive species in the Mississippi River
and threatening the Great Lakes.

Second, many of the shrimp farms in places
like Thailand, the Philippines, and Vietnam
have been built in coastal areas that were
once covered in mangrove forests. These
locations are ideal for shrimp farms because
of the brackish water and flat terrain suit-
able for pond building, but replacing man-
grove forests with shrimp farms leads to the
loss of some of the critical ecosystem func-
tions that mangroves provide, as described
earlier in the chapter.

Third, just as land-based CAFOs have serious waste problems, so too do aquaculture systems.
Wastewater from fish ponds is loaded with nitrogen and phosphorous that can contribute to
harmful algal blooms, eutrophication, and dead zones if it is released from ponds into nearby

Fourth, because farm-raised fish tend to be packed together in small spaces, they are sus-
ceptible to disease and parasites. If not managed properly, these diseases and parasites can
spread to nearby populations of wild fish.

Finally, some types of farm-raised fish (for example, Atlantic salmon) are actually fed fish
meal produced from wild-caught fish species. It’s estimated that as much as one fourth of all
wild-caught fish is converted to fish meal for aquaculture production.

The WRI has published a number of reports that include recommendations for how to make
aquaculture more sustainable (Waite, Beveridge, et al., 2014; Waite, Phillips, & Brummett,
2014). Among the most important of these recommendations are to invest in technology
and innovation in the aquaculture sector and to take a landscape-level approach to locat-
ing and operating aquaculture farms. For example, the WRI recommends that fish farms be
spread out to minimize the concentration of waste products and that aquaculture production
adopt some of the high-tech precision approaches (satellite mapping, GPS) being increasingly
adopted by land-based farmers (see Section 4.10).

Alexpunker/iStock/Getty Images Plus
An aquaculture shrimp farm in Indonesia.

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Section 6.5 Sustainable Management of Ocean and Marine Ecosystems

In addition, the WRI recommends that more aquaculture be focused on producing varieties
of fish that do not require feed made from wild fish—in other words, fish that eat low on the
food chain. For example, fish like tilapia, catfish, and carp can be raised almost entirely on a
vegetarian diet and therefore do not cut into wild fish stocks as carnivorous species do.

Another idea being advocated by the aquaculture industry and some environmental groups
is deepwater aquaculture. Deepwater aquaculture involves locating large underwater cages
filled with farmed fish far offshore. Deepwater aquaculture reduces the water pollution and
habitat destruction problems associated with onshore fish farms because the fish are more
spread out, but it still has the same risks associated with escape and disease transfer.

Regardless of the debate, large-scale aquaculture production is here to stay. The key to its
ability to contribute to the sustainable management of ocean and marine ecosystems will be
determined by the actual practices used in aquaculture facilities around the world.

Ocean and Marine Policy
One of the biggest challenges with achieving sustainable management of the world’s ocean
and marine ecosystems is that most of the ocean is outside the jurisdiction of any one coun-
try. International law allows countries to set an exclusive economic zone (EEZ) 320 kilome-
ters (200 miles) out from their coast and to regulate fishing and other commercial activities
within their EEZ. Ocean water beyond that 320-kilometer EEZ is considered the high seas,
and these areas account for 64% of the ocean’s surface area and 95% of its volume. Manage-
ment and regulation of fishing and other activities on the high seas is virtually nonexistent,
although the United Nations Convention on the Law of the Sea (UNCLOS) is an attempt to
address this. UNCLOS was adopted and signed in 1982, went into effect in 1994, and includes
some provisions focused on overfishing. However, most of these provisions are limited to
what each country should be doing within its own EEZ. While the United States recognizes
UNCLOS as established international law, it is still not technically a part of the agreement,
which was never ratified by Congress.

Within the EEZ of the United States, the Magnuson–Stevens Fishery Conservation and Man-
agement Act, often referred to as the Magnuson–Stevens Act (MSA), is the primary policy tool
for regulating fisheries. The MSA sets up regional fishery management councils that develop
fishery management plans for their region. Fishery management councils consider the degree
to which a specific fishery is overfished and develop plans for restoration if that is the case.
The management councils also set catch limits and quotas, regulate the kinds of equipment
fishing fleets can use, designate certain areas as off limits to fishing, and limit trade or trans-
port of certain types of fish.

In many poorer countries around the world, the problem of pirate fishing—or illegal, unre-
ported, and unregulated fishing—is a serious challenge, even within their own EEZ. Pirate
fishing boats are much more likely to use destructive fishing practices like bottom trawling
and drift netting, and they pay no attention to catch limits, seasonal restrictions, or other
regulations and policies meant to protect fish stocks and ecosystems. The World Wide Fund
for Nature (n.d.) estimates that pirate fishing generates as much as $23.5 billion in revenues
each year and that an inability to enforce fishing regulations and corruption in poorer coun-
tries results in little effort to crack down on this problem.

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Section 6.5 Sustainable Management of Ocean and Marine Ecosystems

Marine Sanctuaries and Community Management of Fisheries
One of the primary means by which we protect wildlife and sustain ecosystems on land is
through establishment of protected areas. National parks, state parks, and other forms of pro-
tected lands are a common feature in countries like the United States and make up a signifi-
cant portion of the land area in many western states. However, the concept of protected areas
has not transferred as easily to ocean and marine ecosystems. (The Apply Your Knowledge
feature box explores how we might prioritize conservation efforts.)

There are two main categories of marine sanctuaries. First, marine protected areas (MPAs)
are designed to regulate some human activities in marine areas for a specific conservation
purpose. For example, an MPA may restrict oil and gas drilling while still allowing some forms
of commercial fishing. Globally, there are over 5,000 MPAs, but these areas only make up
about 3% of the world’s oceans. Furthermore, MPAs still often allow some commercial and
extractive activities, so they are not considered fully protected.

A second category of marine sanctuary is known as a marine reserve. Marine reserves are
much more restrictive of human activities than MPAs, and generally they operate as “no-take
zones” that completely prohibit fishing. Marine reserves are far fewer in number than MPAs,
and they only account for less than 1% of the world’s ocean area. In contrast, marine scien-
tists recommend setting aside somewhere from 10% to 30% of the world’s ocean area as
marine reserves.

Assessments of marine biodiversity and ecosystem health in marine reserves suggest that
marine reserves can be quite effective in sustaining our oceans. Once protections and restric-
tions on fishing are put in place, fish populations, fish size, fish reproduction, and overall biodi-
versity can increase dramatically in just a few years. Because fish move in and out of reserves
constantly, protected areas can help increase fish populations in surrounding waters as well.
The main challenge with establishing and maintaining marine reserves involves patrolling
and regulating access to and use of the area. This is especially the case in some poorer coun-
tries that might lack the resources needed for effective enforcement of marine reserve rules.
In some cases marine reserves, and especially MPAs, can be considered merely “paper parks,”
since they lack the resources needed for effective protection of local marine ecosystems.

One way to enhance protection of marine reserves and MPAs is for governments to partner
with local fishing communities. When these communities are involved in the process of plan-
ning and establishing marine reserves and can see how setting aside some fishing grounds
can improve production in other nearby areas, they are often willing to get on board. Local
fishers know the area and can help provide the eyes and ears needed for effective patrolling
and enforcement of regulations.

Likewise, outside of marine reserves and MPAs, there is evidence that community-based man-
agement of local fishing stocks can be an effective way to sustain them. Community-based
fisheries management, or comanagement of fisheries, is an approach that involves partner-
ship between government agencies, scientists, and local fishing communities. Here too, the
basic idea is that local fishers tend to have extensive knowledge of nearby fisheries, and when
appropriate structures are in place to govern sharing and access, they can work together quite
effectively to achieve sustainable management. A worldwide study of 130 fisheries where

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Section 6.5 Sustainable Management of Ocean and Marine Ecosystems

community-based fisheries management was being practiced found that many of them were
proving effective in moving toward sustainable management of local marine resources (Guti-
errez, Hilborn, & Defeo, 2011).

Apply Your Knowledge: Where Is Ocean Life Most Vulnerable?

The ocean is home to a variety of ecosystems and environments. There are coral reefs,
kelp forests, ocean trenches, mangroves, intertidal zones, and many other ocean habitats
distributed over two thirds of the Earth’s surface. With so many different environments, you
might wonder which ones support the most life, which ones are most threatened by human
activities, and how we should prioritize future conservation efforts.

In Figure 6.5, the world’s oceans are colored to reflect the amount of photosynthesis that
is occurring. To be more specific, this “primary productivity map” shows the amount of
chlorophyll that is contained in organisms like kelp, algae, and plankton. These creatures
are important primary producers in marine ecosystems, and wherever they are located, life
is able to thrive. Using this data, see if you can determine where the most life is located and
whether these locations are vulnerable to human disruptions. Most importantly, see if you can
use what you have learned so far in this chapter to provide explanations for your conclusions.

In Figure 6.5, purple and blue regions represent locations with relatively little life, green
represents areas with some life, and yellow and red locations represent areas that are
densely packed with plants, animals, and microorganisms. As you might have noticed, some
of the ocean’s most biologically dense communities are in shallower coastal regions. Sunlight
is able to reach the seafloor in these environments, where all kinds of photosynthesizing
organisms like coral, kelp, and seagrass reside. These organisms are then able to support
entire ecosystems by providing food and habitat.


Figure 6.5: Primary productivity maps

Where is chlorophyll most concentrated?

Source: SeaWiFs Project, n.d. (https://earthobservatory.nasa.gov/images/4097/global-chlorophyll).

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Section 6.5 Sustainable Management of Ocean and Marine Ecosystems

The Consumer Role
A final way to achieve the sustainable management of ocean and marine ecosystems is to
involve individual consumers. Decisions we make about what types of seafood to purchase
and eat send signals to those who catch, process, and market these products. But given all the
choices out there, how are we to know whether the seafood we are purchasing was produced
in a sustainable fashion?

There are at least three seafood labeling programs that are designed to take some of the mys-
tery out of seafood purchases. By purchasing seafood products that show these labels, you are
supporting fishing operations that have demonstrated that they are operating in a sustain-
able manner.

The first labeling program is known as the Marine Stewardship Council (MSC). The MSC is
what is known as a third-party certification body in that it sets sustainability standards and
assesses whether those standards are being met independent of the company or individual
being assessed. MSC standards focus on three core principles:

Apply Your Knowledge: Where Is Ocean Life Most Vulnerable?

The availability of important nutrients is another reason why coastal areas are full of life.
Freshwater sources carry nutrients from landmasses and deposit them along coastlines.
Ocean currents bump up against continents like North America, South America, and Africa
to create coastal upwelling, and this process brings nutrient-rich water from the deep ocean
up to the surface. When you combine these nutrients with sunlight, you end up with coastal
areas that are teeming with life.

You may have also guessed that many of these coasts are easily impacted by human
activities. Because coastal waters are where many fish and shellfish reside, overfishing and
aquaculture operations tend to disproportionately impact coastal ecosystems. Pollution is
another important risk factor. The sediment, nutrient pollution, and plastics that you read
about earlier in the chapter often enter oceans along coastlines, where they can have major
environmental consequences. Finally, we have human development. Almost half of the
world’s population lives near a coastline, and construction, shipping, nonconsumptive water
use, and even recreation can all harm sea life and destroy habitat. To make matters worse,
limited freshwater resources are now leading some population centers to build desalination
plants. These facilities produce freshwater by removing salts from ocean water. In the
process, many facilities produce thermal pollution and salty waste materials that can damage
coastal habitats.

Primary productivity maps tell an important story about the world’s oceans. Sea life is
concentrated along coastlines due to the availability of light and nutrients. Unfortunately,
these locations are also vulnerable to harmful human activities. With this understanding, we
can begin to appreciate the importance of coastal conservation and other efforts that reduce
human impacts on ocean life.

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Bringing It All Together

1. maintaining sustainable fish stocks
2. minimizing environmental impact
3. promoting an effective fishery management system that respects local, national, and

international laws and regulations

Fishing operations that wish to receive the MSC “certified sustainable seafood” ecolabel must
undergo an audit and certification assessment to see if they meet MSC performance indica-
tors. The MSC has been in operation since 1996, and in that time it has certified thousands of
fishery operations. Despite this success, there have been complaints that the MSC does not
always apply its standards consistently and that some fishery operations that are not really
sustainable have still been able to achieve MSC certification (Zwerdling & Williams, 2013).

A second program, the Aquaculture Stewardship Council (ASC), uses an approach similar to
that of the MSC but applied to aquaculture operations specifically. The ASC core principles
focus on making sure that aquaculture operations minimize their impact on the surrounding
natural environment and that they treat their workers fairly and respect local community
laws and regulations. Specific ASC standards address some of the issues discussed above,
like waste management, accidental escape, disease management, habitat destruction, and
fish feed sourcing. Like the MSC, the ASC is an independent, third-party certifier, and as with
the MSC, it awards a “farmed responsibly” ecolabel to aquaculture operations that meet its

Lastly, the world-famous (thanks to the movie Finding Dory) Monterey Bay Aquarium has
developed a Seafood Watch program to help individual consumers and businesses find sea-
food produced in a way that supports healthy oceans. The Seafood Watch program includes
a downloadable app as well as an extensive website, each with a wealth of information on
how people can make choices that support ocean and marine sustainability. While consumer-
focused programs like the MSC, the ASC, and Seafood Watch cannot always have the same
reach and impact as effective laws and regulations, they can contribute to improving ocean
sustainability through market signals.

Bringing It All Together

We began this chapter with the story of how salmon in the Pacific Northwest are acting
as natural nutrient recyclers, carrying nitrogen and phosphorous from the deep ocean
upstream to fertilize forests and ecosystems hundreds of miles from the coast. Our lives on
land are connected in many ways with what happens in the oceans, no matter how far away
they are or how little we know about them.

This chapter illustrates not only how the oceans affect us but also all the ways in which we
affect the oceans—often with destructive impacts. We are learning more every day about
the dangers our actions pose for the future of the oceans and our own well-being. To avoid
the worst outcomes and to slow or even halt the degradation and destruction of ocean and
marine ecosystems, we need to change the way we do a lot of things on land. For example,
better farming practices and management of waste products from animal feeding operations
can reduce nutrient pollution. Likewise, better solid waste management can help reduce
plastic pollution in the world’s oceans. But of all these possible actions, perhaps none is

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Bringing It All Together

more important than reducing rates of ocean warming and acidification. To do that we need
to make fundamental changes in the way we produce and use energy, and that issue is the
focus of the next chapter.

Additional Resources

Our Oceans

The National Oceanic and Atmospheric Administration and the Woods Hole Oceanographic
Institution are two excellent sources for all kinds of information on the oceans and ocean life.

• https://www.noaa.gov
• https://www.whoi.edu

These three TED video lectures are a good way to begin to understand just how vast and
magnificent the oceans are, as well as what some of the major threats to those oceans are.

• Sylvia Earle: TED Prize Wish: Protect Our Oceans:

• Paul Snelgrove: A Census of the Ocean:

• Graham Hawkes: Fly the Seas on a Submarine With Wings:

Ocean Currents

These two short videos provide a great explanation of ocean currents and the Coriolis effect.

• TED-Ed: How Do Ocean Currents Work?:

• https://ocean.si.edu/planet-ocean/tides-currents/ocean-currents-motion-ocean

Plastic Pollution

There is growing evidence that plastic pollution of the oceans and waterways is reaching cri-
sis proportions and that as plastic breaks down, it turns into microplastics that are entering
the food chain and even human bodies. These links detail the extent of the problem.

• https://www.npr.org/sections/thesalt/2019/06/06/729419975/microplastics

• https://www.npr.org/sections/thesalt/2018/08/20/636845604/beer-drinking

• https://marinedebris.noaa.gov

Researchers are still learning about the implications microplastics have for human and envi-
ronmental health, but these links describe some of the known and suspected risks.

• https://blog.response.restoration.noaa.gov/plastic-pollution-and-human-health

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Bringing It All Together

• https://www.scientificamerican.com/article/from-fish-to-humans-a-microplastic

• https://www.ciel.org/reports/plastic-health-the-hidden-costs-of-a-plastic-planet

Scientists aren’t the only ones trying to address the plastic pollution problem. Read about
one man’s efforts, and consider how you might impact your own community.

• https://www.npr.org/sections/goatsandsoda/2019/01/15/683734379/an-island

The connection between ocean currents, gyres, and ocean garbage patches can be a little dif-
ficult to understand. These sources help explain the concept and provide examples.

• https://marinedebris.noaa.gov/info/patch.html
• https://oceanservice.noaa.gov/podcast/mar18/nop14-ocean-garbage-patches.html

Noise Pollution

These links provide additional information on the problem of ocean noise pollution.

• Kate Stafford: How Human Noise Affects Ocean Habitats:

• https://e360.yale.edu/features/how_ocean_noise_pollution_wreaks_havoc

Ocean Acidification

Ocean acidification has been called “climate change’s equally evil twin” because of the
potential damage it can do to marine life and the planet. There are many resources available
to better understand this somewhat complicated issue, including these.

• https://blogs.ei.columbia.edu/2015/12/09/what-is-ocean-acidification-why

• https://ocean.si.edu/conservation/acidification
• https://www.noaa.gov/education/resource-collections/ocean-coasts-education

• https://www.iucn.org/resources/issues-briefs/ocean-acidification

Marine Sanctuaries

This global, interactive map of marine protected areas and TED Talk arguing for a substan-
tial expansion of those areas are very interesting.

• http://www.mpatlas.org/map/mpas
• Enric Sala: Let’s Turn the High Seas Into the World’s Largest Nature Reserve:

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Plastic & Health: The Hidden Costs of a Plastic Planet (February 2019)

Plastic & Health: The Hidden Costs of a Plastic Planet (February 2019)















Bringing It All Together

Key Terms
aphotic zone The region of a
body of water that is beyond the
reach of light from the surface.

aquaculture The cultivation of fish,
shrimp, and other marine life in ponds,
pens, cages, and other confined settings.

atmospheric deposition The
process by which air pollutants
fall to the Earth’s surface.

benthic zone The region at the bottom
or lowest level of a body of water.

bioaccumulation The buildup of toxins
in an individual organism over time.

bycatch The accidental capture and death
of nontarget species in fishing, including
dolphins, sea turtles, and seabirds.

coral bleaching The whitening
of corals that occurs due to the
loss of zooxanthellae algae.

Coriolis effect The tendency for currents
to move to the right in the Northern
Hemisphere and to the left in the Southern
Hemisphere because of the Earth’s rotation.

El Niño–Southern Oscillation
(ENSO) A recurring climate pattern
that changes ocean currents and
disrupts typical weather patterns.

estuaries Bodies of water in
which freshwater from rivers mixes
with salt water from the sea.

Great Pacific Garbage Patch
(GPGP) The collective name for two
garbage patches in the North Pacific
Ocean that have formed as a result of
plastic pollution and ocean currents.

Gulf Stream The major ocean current
that brings warm water from the
tropical regions around Florida to the
northeastern United States, northeastern
Canada, and northern Europe.

gyre A large-scale circular ocean current.

intertidal zone The region where
a body of water meets the land.

mangrove forests Groupings of
mangrove trees and other vegetation
that grow in coastal intertidal zones.

marine protected area (MPA) A type
of marine sanctuary designed to regulate
some human activities in marine areas
for a specific conservation purpose.

marine reserve A type of marine
sanctuary that generally prohibits fishing
and other commercial activities.

marine snow The slowly sinking shower
of organic material in the ocean.

microplastics Very small pieces of plastic
formed as larger pieces of plastic pollution
undergo photodegradation and break apart.

ocean acidification The process by
which the ocean becomes more acidic
as a result of carbon dioxide combining
with seawater to produce acid.

ocean noise pollution Excessive
underwater environmental noise
that can harm marine health.

pelagic zone The region of a body
of water that is not associated with
the shore or with the bottom. In the
ocean, this is the open ocean zone.

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Bringing It All Together

photic zone The region of a body of
water where light can penetrate.

photodegradation The process in
which materials are broken down
into smaller pieces by sunlight.

phytoplankton Microscopic marine algae.

salt marshes Shallow wetlands that are
flooded with salt water during high tides.

surface currents Ocean currents that
move water horizontally along the surface.

thermohaline circulation Vertical
movement of water caused by differences
in temperature and salinity.

upwelling An oceanic phenomenon
that involves the rising of cold,
nutrient-rich water.

vertical currents Ocean currents that move
water between the surface and the depths.

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Sustaining Biodiversity and Ecosystems 
Institutional Affiliation
Student’s name

Food Resilience Plan for Ashfordton
An idea that I have to promote food resilience is to create avenues whereby young people with farming skills and experience can acquire farmland through zero-interest mortgages. If new farming businesses and communities are supported by investors until they are established they would in turn focus on promoting their long term economic and environmental benefits which is the production of healthy food without impacting the ecosystem.
Secondly, to improve nutrition we need to make food supplies more diverse, nutritious and sustainable. This refers to rebalancing agricultural production from mono crops and cereals, towards more diverse production of fruits, vegetables and semi-arid nutritious crops.

6 different pro’s

Response for Terry Brandt
I like this idea of composting as it will reduce the need for commercial fertilizers which degrade the soil.
Response to Lisa Edridge
By ensuring that surface runoff is not contaminated with trash and debris, the water can be recycled or stored to farming activities.
Response to Sharon Lane
Planting of these crops will not require a lot of farm input since these products do not deplete the soil in comparison to cash crops.
Response for Lisa Eldridge
Supporting local farmers motivates them to increase output
Response to Lisa Eldridge
Encouraging fresh food vendors to purchase locally reduces the food mileage by making the community self-sufficient in regards to nutrition.
Response to Erica Tucker
A community garden through land restoration allows use of existing natural based solutions for safeguarding biodiversity and successful agro-ecological practices.

6 different con’s

Response for DeEdmund Nettles
Abandoned areas could be contaminated by chemical and inorganic particles which can lead to the production of contaminated produce.
Response for Remon Berry
Creating and using the available ingredients to cook could lead to malnourishment since some supplement are only available in specific crops.
Response to DeEdmund Nettles
Birds are carriers of numerous pests and diseases; they can introduce a harmful organism to the crops reducing the yield or necessitating farmers to plant a different crop.
Response for Remon Berry
Storing of vegetables for a long period in freezer requires space for setting up the facility and the process utilizes a lot of power to maintain temperature of produce.
Response to Keshena Mobley
Solar infrastructure requires technical expertise during installation and maintenance to ensure they have high efficiency of output.
Response to Keshena Mobley
Locally purchasing food could lead to the elimination of the supply chain infrastructure supplying that particular community which could affect the supply of produce which is not locally available.

Locally purchasing food could lead to the elimination of the supply chain infrastructure supplying that particular community which could affect the supply of produce which is not locally available.

Running head: DISCUSSION 1 1
Discussion 1
Institutional Affiliation
Student’s name

Water Management Plan for Ashfordton
Original ideas.
One idea I have is that I would recommend to the community of Ashford to construct a water catchment reservoir away from the populated areas which would be used to store flood and rain water from the mountains.
I would also recommend to the community that they should reclaim water to alleviate the stress on primary water resources. Reclamation process can involve pumping water from underground reserves and taken to a recycling facility whereby it is treated and distributed to the community.


Terry Brandts
A rainfall-runoff reserve allows the community to have a waterbody providing sufficient water to be utilized during the dry season.
Remon Berry
Rooftop water harvesting is cheap and convenient for the residents
Remon Berry
Rooftop water harvesting allows each member of the community participates in sustainable water management measures by doing their part.
Remon Berry
Potable water is a storm management measure that can be easily adopted by Ashfodton residents since its simple and cheap.
Remon Berry
Potable water is convenient since residents can store as much water as each one’s need requires. Therefore, it is adaptable to each resident’s water demands.


Erica Tucker
A dam requires expensive equipment to construct.
Erica Tucker
A dam requires a lot of available space to construct.
Terry Brandts
A retention pond can be contaminated by algae and microorganisms compromising the quality of the water
Erika Tucker
A rain garden requires human and equipment resources to construct.
Erika Tucker
A rain garden has the potential of drying out due to the high temperature and low humidity experienced in Ashfordton.
Remon Berry
Rooftop rain water harvesting may lead to the collection of water contaminated by atmospheric gases and fumes since the city of Ashfordton is highly populated and produces fumes from production of energy by using coal.
Terry Brandt
There may not be enough open spaces to plant trees. Also, trees are not a measure that will alleviate the water management measures in Ashfordton since trees take too long to grow and their impact may be minimal.

Bensel, T., & Carbone, I. (2020). Sustaining our planet
. Retrieved from https://content.ashford.edu

Carolina Distance Learning. (n.d.). Ground and surface water interactions [Investigation manual ]. Retrieved from https://ashford.instructure.com

Chemistry & Sustainability – American Chemical Society. American Chemical Society. (2020). Retrieved 25 June 2020, from https://www.acs.org/content/acs/en/sustainability/understandingsustainability/sustainable-water.html

Earle, S. (2013, December 6). Ocean 2050: How to sustain our biggest ecosystem (Links to an external site.). Retrieved from http://www.bbc.com/future/story/20131206-sos-save-our-seas

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