In addition to our usual Congressional Research Service (CRS)
Reports and Issue Briefs, we are featuring an introductory essay by Gale
Mead Hey on the link between human populations and the world's oceans.
Available in in-depth and abbreviated
versions, the essay addresses the primary ways in which human population
impacts the world's oceans. A glossary is appended to the longer version.
The first CRS report, Social Aspects of
Federal Fishery Management (April 21, 1995) explores historical
and current concerns of the federal government's fishery management
effort. The social effects of fish catch downsizing as well the conflicts
between resource management and the fishing industry is explored.
The second report is Overcapitalization
in the U.S. Commercial Fishing Industry. This report deals
more explicitly with the core issue of over-fishing of ocean fish
stocks. The possibility of a change in federal policy to
discourage investment in the overcapitalized industry is
examined. The nature of access restriction, and its
implementation, is addressed.
The transnational nature of the problem of fishery stocks,
acknowledged in the last report, is directly addressed in the
next report. Agreements to Promote Fishery
Conservation and Management in International Waters notes the
absence of regulation and enforcement of fish catch quotas in
international waters and their subsequent depletion. Agreements
serving as a corollary to the Law of the Sea Convention seek to
rectify this. By implementing a framework to develop
technological and scientific cooperation, the subscribing
governments hope to address the conservation and management of
fish stocks. A non-binding Code of Conduct for Responsible
Fisheries, developed by the United Nations Food and Agriculture
Organization (FAO), represents the culmination of these efforts.
The movement toward reflagging of fishing vessels to increase
international accountability is a further, tangible effort to
address this problem.
The Congressional Research Service is a part
of the Library of Congress and is not affiliated with the CNIE or
The primary legislation governing Federal fishery management, the Magnuson Fishery Conservation and Management Act, contains references to the social aspects of Federal fishery policy. Many of the references have an historical basis resulting from the inherent social conditions and values associated with the fishing community. Other applicable laws, as well as Federal emergency and financial aid programs, contribute to an understanding of the overall Federal policy toward social issues as they relate to fishery management.
At issue is whether the Federal Government should examine its approach to the social aspects of fishery management. Because crucial decisions concerning the future of fishery management are on the horizon, a window of opportunity may exist for evaluation of the Federal role. Overfishing and/or overcapitalization may force fishery managers to adopt strategies (e.g., downsizing) that will have inevitable social repercussions. How social concerns are reflected in fishery legislation will influence how fishery management plans respond to overriding issues, such as resource conservation. A basic conflict may exist between the objectives of resource conservation and a manager's obligation to consider the social consequences of his/her actions.
This report examines historic and current references to the social aspects of fishery management as they appear in legislation, and discusses the importance of considering these issues. A discussion of possible alternative approaches, with regard to the role of the Federal Government, follows.
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Living marine resources -- fish and shellfish -- are among the economically dominant features of the world's oceans as well as vital sources of protein for the world's people. However, the sustainability of these essential resources is at risk. As a result of increased demands for fish products and expansion of fishing fleets, many traditional fisheries around the world are now depleted.
As with many nations, U.S. marine fisheries managers have struggled to maximize harvests while maintaining productive stocks. Early attempts at management were compromised by largely unregulated foreign and domestic fleets. By 1976, the overexploitation of several stocks in offshore U.S. waters led to the passage of the Magnuson Fishery Conservation and Management Act (MFCMA), with the prevention of overfishing acknowledged as the first of the Act's seven national standards for new fishery management plans.
Since 1976, increases of 40 percent in the number of fishing vessels and 60 percent in the number of fishermen employed in commercial fisheries have yielded an increase of 50 percent in catches. Such growth, largely attributable to higher levels of consumer demand, government encouragement and assistance, and technological advances, has given U.S. fishermen continued incentive to further expand their capacity to fish. Capital invested in this expansion, however, has not yielded the anticipated returns. By 1993, 65 of a total 231 U.S. marine fish stocks were classified as overfished with the livelihood of the Nation's fishermen becoming as threatened as the fish they seek. With too many fishermen vying for too few fish, the U.S. commercial fishing industry is becoming as overcapitalized as the resource is overfished.
Scientists, managers, and industry experts have begun re-evaluating traditional models and techniques for managing fishery resources. Under closest scrutiny is the traditional open access approach to fishery resource use. Some critics insist that, in the absence of some effective form of property rights, marine fish stocks will continue to diminish. A management regime that addresses open access concerns appears warranted, as does an overall reduction in fishing capacity. Nevertheless, significant questions remain. In particular, how and in what form should access be addressed? In what sector(s) and by what means ought reductions in capital invested in the commercial fishing industry occur? And, what is the role of the Federal Government in such proceedings? These questions and several others await careful evaluation by scientists, conservationists, industry experts, and lawmakers alike, while the fates of fishermen and the fish they depend upon hang in the balance.
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Declining fish populations threaten an important food source. Natural catastrophes, pollution, habitat destruction, and overfishing contribute to the depletion of fish stocks. Overexploitation of fishery resources often occurs when management allows expanding and increasingly efficient fishing fleets to continue harvesting dwindling supplies.
International law acknowledges the right of states to exploit fishery resources in international waters. However, the 1958 Geneva Convention on the High Seas requires that such practices be conducted in consideration of other states' interests, including a basic obligation to cooperate in the conservation and management of living marine resources. However, the absence of formal regulations for fishing in international waters has encouraged states to exploit living marine resources without considering the sustainability of their catch quotas. Cooperative efforts to conserve fishery resources often were circumvented or not enforced.
As fish stocks have diminished, the international community has recognized that several issues needed to be addressed. These included the practice of reflagging fishing vessels and the management of straddling and highly migratory fish stocks. The Agreement to Promote Compliance with International Conservation and Management Measures by Fishing Vessels on the High Seas promotes sustainable international fisheries by addressing fishing vessel reflagging. The accountability principles outlined in this Reflagging Agreement are the cornerstones of a further Agreement for the Implementation of the Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 Relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks. This second Agreement creates a framework within which regional arrangements are to be developed to cope with conservation and management concerns, relying on international technological and scientific cooperation. A non-binding Code of Conduct for Responsible Fisheries, developed by the United Nations Food and Agriculture Organization (FAO), represents the culmination of these efforts.
All of these recently negotiated agreements extend provisions of the 1982 United Nations Convention on the Law of the Sea (UNCLOS) to promote better international fishery conservation and management. Through these agreements, the United States has an opportunity to ratify and implement several less-controversial provisions of UNCLOS. The United States has already implemented the Reflagging Agreement through Title I of P.L. 104-43. The Agreement Relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks was signed by the United States on December 4, 1995, and will soon be transmitted to the Senate for advice and consent.
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|Population & Environment Linkages: Oceans
Short Introduction by Gale Mead Hey
The effects of human activity on marine ecosystems and life have become increasingly apparent in recent decades. The ways in which humans have affected the world's oceans include:
1) Direct physical alteration of ocean environments
2) Extraction of living and non-living resources
3) Pollution of ocean environments
4) Introduction of alien species
5) Global climate change
Each of these are described in detail in Troubled Waters, a statement signed by over 1,600 marine scientists and conservation biologists from 65 countries. For the purposes of this discussion, the question to be addressed is how human population contributes to these sources of ecological harm.
Population plays a role in direct physical alteration of ocean environments in terms of global population growth, but more importantly because 66% of the world's 5.8 billion humans live within 100 km of the ocean, and populations in coastal zones are increasing at a much faster rate than overall population growth. As more coastal areas are developed for human habitation, critical habitat and breeding grounds for marine species is degraded or destroyed. Dams, sea walls, golf courses, shrimp farms, homes, and shopping malls alter the ecology of coastal zones. Another form of physical alteration is bottom trawling, a fishing method with effects comparable to clear-cutting of forests. As discussed below, population growth fuels demand for seafood, including those species which are obtained by bottom trawling.
Overexploitation of marine resources includes commercial fishing, extraction of mineral resources, and exploitation of marine mammals. Demand for these resources is driven in part by cultural, economic, and political forces, but also by increased population. At the most basic level, it takes more resources to meet the needs of six billion people than to meet the needs of one billion. Humans currently consume 13 kg of fish per capita each year. Fish protein currently constitutes 19% of humans' animal protein intake, and the FAO predicts that as population increases, demand for seafood will increase accordingly. The FAO has stated that virtually all of the world's commercial fisheries are either overexploited or fully exploited.
Pollution of ocean environments is both direct and indirect. It is estimated that the runoff from 90% of the Earth's land mass ultimately makes its way into the ocean, including fertilizers, pesticides, herbicides, heavy metals, and sewage. Air pollution is eventually carried into the ocean with rain and snow, and marine waters are polluted directly via oil spills, ocean dumping, and release of sewage. While the contributing factors are diverse and complex, population growth plays a significant role. It would be too simplistic to state "more people equals more pollution," but the extent of the damage caused by marine pollution is largely a problem of scale brought about by the fact that there are 5.8 billion of us.
Introduction of alien species occurs when species from one part of the world are transported into a new environment, where their natural competitors, parasites, and predators do not exist. Most marine alien species are introduced by being sucked up into ships' ballast tanks, then expelled when the tanks are emptied, in distant waters. The relationship to population is that population growth has contributed to a global increase in shipping. Depletion of local resources (including grain, wood, fuels, materials for consumer goods, etc.) in many areas of the world has outstripped global population growth rates. Places that were formerly self-reliant now depend on imports to meet their requirements. Driven in some cases by local depletion and in others by affluence, the needs of Earth's current human population are largely met by moving products and resources around the globe.
Global climate change is now acknowledged to be a significant problem, caused at least in part by human activities. As the world's human population has increased, so has use of fossil fuels and other pollutants which contribute to global climate change. While significant climate changes have occurred naturally throughout the Earth's history, humans' activities are accelerating the rate at which climate change is now occurring. Species and ecosystems which may be capable of adapting to slow climate change may be unable to adapt quickly enough to survive.
The relationship between human population and the negative effects of human activities on the oceans is largely a matter of scale. Marine ecosystems are capable of surviving a limited amount of fishing, pollution, and habitat destruction, but there is increasing documentation that they cannot sustain the amount of pressure currently being placed on them. Human activities are continuing to cause changes so quickly that scientists are hard-pressed even to study them, let alone ameliorate their effects.
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|Population & Environment Linkages: Oceans
Long Introduction by Gale Mead Hey
Seen from afar, Earth is a water planet. The world's oceans cover
77% of the Earth's surface, comprise 99% of the planet's biosphere,
and contain far greater diversity of life than is found on land
(3). Even the most biologically rich tropical rain forests cannot
match the biodiversity found in a coral reef community (based
on the number of major categories of life represented). The oceans
are so vast, and so full of life, that it has always seemed impossible
that humans could have any appreciable impact on their functioning,
or on the species that live in the deep. Many people assume that
if land-based resources are ever depleted, the oceans will remain
a virtually limitless resource which can feed humanity and meet
the needs of a growing population.
But especially within the last 30 years, increases in human population,
combined with improved technology, increased demand for seafood,
use of products that directly or indirectly contribute to pollution,
and a host of other factors, have led to impacts on marine ecosystems
that could not have been imagined 100 years ago. As the Earth's
human population approaches six billion, scientists, economists,
policy makers, and the general public have begun to observe increasing
evidence of the pressure humanity is placing on the ocean's natural
systems and resources (23).
Human activity has influenced the nature of ocean resources and
the functioning of the sea for centuries, but only in recent decades
has an understanding of the complicated relationship between human
population and oceans begun to come into focus. While much more
needs to be done to assess the long-term impact of human activity
on the ocean --- globally, regionally, and locally --- marine
scientists have identified the following five areas of concern
Each of these topics is considered here with special reference
to the role of human population levels. However, the effects of
human population are inextricably linked with the impact of political,
cultural, economic, and other factors, and effects of population
must be considered in the context of these other factors.
- Direct physical alteration of ocean environments
- Extraction of living and non-living resources
- Pollution of ocean environments
- Introduction of alien species
- Global climate change
Human activities physically alter the seabed directly in a variety
of ways, including dredging, trawling, and boat groundings, and
indirectly by deforestation, damming, erection of sea walls, and
other activities that increase sedimentation and/or cut off the
natural exchanges between land and sea. Alteration of the coastal
landscape can be profound, as major urban centers, resorts, hotels,
golf courses, ports, and factories replace natural coastal ecosystems.
Approximately 60% of the world's population currently lives within
60 km (37 miles) of coastal waters, and the coastal population
is expected to double within the next 30 years (1). Cultural trends
and economic pressures are driving many people from rural areas
towards the major urban centers, most of which are located in
coastal areas. Fully 2/3 of the world's urban centers (cities
with populations over 2.5 million) are near tidal estuaries, and
six of the world's eight megacities (cities with a population
over 10 million) are coastal (11). Paradoxically, the shift to
coastal regions is driven both by poverty and affluence, as poor
people move to urban centers seeking a livelihood, and wealthier
people spur new development along the shoreline, such as coastal
resort hotels, and homes with a view of the sea.
Coastal zones are acknowledged to be among the most biologically
productive habitats on earth, and with the increased rate of human
population growth in coastal areas greatly outpacing overall population
expansion, they are also among the most impacted. The World Resources
Institute estimates that roughly half of the world's coastal ecosystems
are threatened by development, with most of those threatened located
in northern temperate and northern equatorial regions, including
most of the coastal zones of Europe, Asia, the United States,
and Central America (24).
As coastal areas are developed for human use, critical habitat
for seabirds, marine mammals, and other marine species is reduced
or eliminated. Shallow harbors are dredged to make them navigable.
Sea walls cut off the natural exchange between land and sea. Rivers
are dammed, cutting off critical migration routes for species
such as salmon and blue crab, which need both fresh and salt water
habitats to survive.
Physical changes along the coastline can also impact species
and systems in the open ocean, particularly among species that
spend part of their life cycle nearshore, onshore, or inland.
Definition of the nature and extent of these effects has only
just begun, and much more study will be necessary to develop a
better understanding of these issues.
A less visible, but more widespread source of physical alteration
of the marine environment is caused by the fishing method of bottom
trawling. Bottom trawling involves dragging weighted nets across
the sea floor, disturbing whatever rocks, coral, and organisms
are in their path. Fish that rely upon hiding places among rocks
and coral reefs find themselves homeless; coral which requires
clear, clean water to survive becomes choked with silt; and ecosystems
that support the very fishery behind the trawling are substantially
The ecological effect of bottom trawling is often compared to
clear-cutting of forests, but while a forest is clear-cut once,
a given area of sea floor may be bottom-trawled 100 times in a
single year. It is estimated that an area equivalent to the world's
continental shelf is trawled every two years. Scientists estimate
that 60 to 95% of the organisms scooped up by bottom trawlers
are bycatch: Non-target species taken incidentally and usually
Other sources of physical disturbance of the seabed include:
undersea mining operations, offshore oil exploration, and other
types of resource extraction activity, ship groundings, and anchorage.
The impact of these sources of disturbance on marine life has
received very little study.
Physical damage to coral reefs and other ecosystems from boat
anchorage and groundings may appear to be small and localized,
but there is evidence that the cumulative effects, particularly
in light of substantially increased frequency in recent decades,
can be significant. For example, the Florida Keys National Marine
Sanctuary receives reports of over 40 boat groundings per month
within the sanctuary's boundaries. Based on observation of damaged
reefs and seagrass beds, there are numerous additional groundings
which go unreported. The damage to highly sensitive coral reef
ecosystems from such frequent groundings can be profound (a).
Dynamite fishing is another form of physical alteration that
devastates coral reefs and reef communities. Fishers explode dynamite
on coral reefs to kill and stun fish, which can then be scooped
from the water with nets. The explosions kill everything near
the blast, including corals. Another technique, called muro ami,
involves pounding reefs with heavy weights to scare fish out of
their hiding places, destroying the coral heads in the process.
To capture fish for the aquarium trade, and for the growing seafood
market for live fish, reefs are deliberately poisoned with sodium
cyanide, rotenone, or sodium hypochlorite bleach killing or injuring
corals, fish, and other reef inhabitants (12).
These techniques are especially common in developing countries
where regulations are often weak and poorly enforced, and the
acute need to put food on the table often outweighs concerns about
the effects those methods will have on the reef's ability to continue
to provide sustenance in the future, let alone concerns about
biodiversity and the health of the oceans (17).
Extraction of Living and Non-Living Resources
Overexploitation of marine resources includes overfishing, extraction
of mineral resources, and exploitation of marine mammals. Potential
effects of these activities are not limited to the removal of
quantities of that resource, but also to possible side-consequences,
such as accidental release of crude oil during the extraction
process, and physical alteration of the sea floor with deep sea
mining operations and bottom trawling. As with most issues involving
the interactions among the human population and the marine environment,
there are multiple causes and effects that are interrelated. Each
issue therefore requires investigation in the context of the larger
Few would question the importance of living marine resources
to humans. Fish and shellfish provide a valuable source of food
protein to our diets, and a livelihood to fishermen and others
in the seafood industry. Other marine resources similarly meet
the needs of the general population, and provide jobs. The issue
at hand is the extent to which we can realistically expect the
oceans to continue to meet those needs, and it is that issue which
drives a pressing need for scientific study, and implementation
of management principles based upon the results of such research.
Fish protein constitutes 19% of humans' animal protein intake
(1), and per capita, humans consume an average of 13 kg of fish
per year (21). The amount is higher in impoverished coastal populations
which rely heavily on local catches, and in affluent societies
with the means to import fish to meet local demand. In Hong Kong,
per capita fish consumption is 100 pounds per year, mostly imported
from elsewhere in Asia and beyond (17). The Food and Agriculture
Organization of the United Nations (FAO) predicts that the global
demand for fish will continue to increase with population growth.
Modern approaches to fishing and transportation make it possible
to catch fish anywhere in the world, and transport them fresh
to wherever there is demand. It can be confusing for consumers
to hear that swordfish or grouper are in trouble when those species
still appear on restaurant menus and in grocery stores. The globalization
of the fish market tends to insulate residents of industrialized
countries from the effects of overfishing, and helps to perpetuate
the myth of the "bountiful, endless potential of the sea
to feed us all." Substantial evidence in recent years has
demonstrated that we can no longer continue making such assumptions
about the world's oceans (2).
Global fishery landings increased fivefold from 1950 to 1989,
peaked at 86 million tons in 1989, and subsequently declined,
in spite of increased demand, an expanding fishing fleet, and
more powerful technology (3). Increases in total fish landings
since 1995 are largely a result of increased aquaculture, which
now accounts for 15.5% of all fishery landings (21), and continuing
increases in the exploitation of species which were previously
regarded to be of little or no commercial value. While landings
of 91 million tons in 1995 suggest the world's fisheries are doing
well, there have been substantial qualitative changes. Populations
of many of the larger species, larger specimens within a given
species, and those higher on the food chain have continued to
decline, and in many cases have ceased to be commercially viable
Many commercial fisheries have collapsed; in 1993 the FAO estimated
that more than 2/3 of the world's commercially valuable fish populations
are overexploited or "fully exploited (21)." The 1991
National Fisherman Yearbook noted: "At present, 45 of the
190 fish stocks that provide 90% of the world's fish production
are overexploited." Technological advances, management issues,
economic forces, and cultural factors contribute to overfishing.
All of these factors interact with one another, and with what
is possibly the most influential factor: The increasing demand
for living resources driven by a growing population.
Atlantic swordfish are old enough to reproduce only after they
have grown to approximately 100 pounds in size. Yet they can be
taken legally at only 33 pounds. Humans are eating the juveniles,
while landings of adult swordfish have become increasingly rare
(b). Landings of Atlantic cod declined from their 1970 high of
3.1 million tons to only 1.1 million tons in 1993, despite increased
effort and improved technology (14). In 1991, an assessment of
western Atlantic bluefin tuna showed that the adult breeding population
had been reduced by 90% in the 20 years since their take had begun
to be regulated. The regulations had been intended to ensure healthy
populations of bluefin tuna, but gave every appearance of having
had the opposite effect, as quotas had been set too high, and
there was evidence of poaching which further depleted the population
of bluefin (3).
In some cases, the decline in fishery catches for a particular
population may be attributable to causes other than overfishing,
such as natural cyclic variations in population, ocean currents,
algal blooms, oil spills, or decline in that species' food supply.
For example, the Black Sea anchovy population, already weakened
by overfishing, was decimated by the introduction of a non-native
species of comb jelly which competes with anchovies and feeds
on their young. However, for the vast majority of those commercial
species which have substantially declined in recent years, overfishing
can be clearly demonstrated to be the main causal factor (21).
Hunting of marine mammal populations provides a clear illustration
of the effects of overexploitation by humans. European whalers
in the 12th through the 16th centuries depleted the northern right
whale populations which could be found in Atlantic coastal zones.
Subsequent advances in boat and harpoon design during the 1700's
and 1800's enabled whalers to exploit the most remote reaches
of the whales' ranges, and by the time right whales were given
protection from hunting, in 1932, scientists estimated that only
100 right whales remained in all of the North Atlantic Ocean,
a population reduction of over 99% (4).
After 65 years of protection, the northern right whale population
is now estimated at approximately 350, reflecting a much slower
recovery than was anticipated. Moreover, DNA studies of over 100
northern right whales revealed evidence that all of the individuals
tested were descended from only three females. Such extreme loss
of genetic diversity can substantially weaken a species' adaptability
and long-term viability (4).
The white abalone provides another example of similar rates of
population depletion due to overexploitation in much more recent
times. In southern California, as supplies of popular pink and
red abalones were depleted in the early 1970s, divers explored
deeper reefs for the even more valuable white abalone. The commercial
white abalone fishery reported landings of 60 metric tons in 1972
alone. Over the next seven years, landings swiftly declined to
near zero. In the early 1970's, surveys documented more than 4,000
white abalone per acre on reefs at depths of 80 to130 feet around
the Channel Islands. Surveys in 1996 revealed only an average
of 0.4 per acre. Thus, white abalone populations have decreased
99.99% in the last 25 years, with an estimated remaining population
of less than 600 individuals. A captive breeding program currently
being developed may be the species only chance for survival (1).
Aquaculture would appear to present a promising means of meeting
the global demand for seafood, as well as cultivating organisms
to restore depleted natural populations. However, the industry
comes with its own set of problems, including destruction of mangrove
forests for shrimp farms, introduction of alien species, disease,
and contaminants, and other forms of damage to local ecosystems.
In addition, some farm-raised species, such as salmon, are carnivorous,
requiring a fish-protein-based diet which is almost always supplied
by wild-caught fish (21).
Fisheries in many regions of the world's oceans remain unregulated
and inadequately studied, and even where research has been done,
political and economic pressures have been known to override scientists'
recommendations. For example, the New Zealand orange roughy fishery,
which started in the 1970's, began to show signs of significant
decline less than 10 years after fishers started pursuing that
species. In 1986, scientists in New Zealand warned that the without
an 84% reduction in the take of orange roughy, the fishery was
at risk of crashing within five years. Policy makers instead chose
not to cut quotas at all for two years, and implemented only a
20% reduction for 1989. Eventually, the New Zealand orange roughy
fishery did collapse, and because orange roughy take 25 to 30
years to reach maturity, populations will be very slow to recover.
To meet the demand for orange roughy, other populations, in unregulated
waters, are now being exploited at rates that are similarly unsustainable
Incidental taking and killing of non-target species, including
fish, marine mammals, and sea birds, has impacted ocean ecosystems.
FAO estimates for 1988 through 1990 indicate an average of 27
million metric tons of fish per year was discarded as bycatch
by commercial fishermen, an amount equal to 1/3 of the total global
landings for each of those years. This figure does not include
the incidental killing of several hundred thousand sea turtles,
marine mammals, and seabirds each year (12). Fishing methods such
as bottom trawling, gill netting, and longlining are especially
prone to bycatch. Shrimp trawlers catch and discard an estimated
nine pounds of non-target species for every pound of shrimp caught
Modern fishery management sometimes succeeds in preventing overexploitation
of the magnitude seen with the right whale, bluefin tuna, and
white abalone. Scientific study can assist policy makers in determining
levels of taking which can be sustained on a long-term basis.
However, much more research is needed in order to ensure the accuracy
of those estimates, and to direct management efforts.
As the human population has increased, so have the following:
The amount of sewage produced; the amount of fertilizers, herbicides,
and pesticides used to raise crops and groom yards, golf courses,
and parks; the amount of fossil fuels extracted and burned; the
amount of land deforested and developed; and the various by-products
of manufacturing and shipping generated. Cultural, political,
and socioeconomic forces influence the kind and amount of waste
and toxics produced, and affect how they are dealt with. Thus,
increased population is clearly just one factor that contributes
to pollution. As with other ways in which humans impact the environment,
the causes and effects are complex.
Pollution of marine ecosystems includes runoff from land, rivers,
and streams, direct sewage discharge, air pollution, and discharge
from manufacturing, oil operations, shipping, and mining (5).
As discussed earlier, the human coastal population already comprises
60% of the world's population. The number of people living within
50 miles of the sea is expected to double within 3 decades (11).
Many cities and towns have found their infrastructure inadequate
to the increased demands placed on them. Sewage treatment facilities
that were adequate a decade ago may literally overflow, discharging
untreated sewage into rivers and oceans.
Although coastal populations have the greatest per capita impact
on ocean ecosystems, pollution from runoff is not limited to coastal
cities. Runoff from over 90% of the Earth's land surface, inland
as well as coastal, eventually drains into the sea, carrying with
it sewage, fertilizers, and toxic chemicals. Similarly, air pollution
from inland as well as coastal cities, including by-products of
fossil fuel consumption, PCBs, metals, pesticides, and dioxins,
eventually finds its way into the oceans after rain or snow. Effects
include water quality degradation, sediment contamination, and
human health risks from contaminated fish and shellfish (c).
Increased demand for oil has resulted in increased offshore oil
extraction operations, and transport of oil, which in turn has
led to more frequent oil spills. The frequency of oil spills in
and near US waters increased from 371,000 spills in 1970 to 921,000
incidents in 1986, with a total of 321.5 million gallons of oil
spilled in and near US waters during that period. However, spills
account for only 10% of marine oil pollution. At least 50% of
the oil pollution in marine waters comes from low-level chronic
sources such as leaks at marine terminals, disposal of drilling
muds from offshore oil operations, runoff from land, and atmospheric
pollution from incompletely burned fuels (15).
The cumulative effects of pollution on ocean ecosystems can be
profound. For example, in the Gulf of Mexico, the occurrence of
what scientists call "dead zones" in once highly productive
waters can be traced to the introduction of excessive nutrients
from farms, lawns, and inadequately treated sewage, which stimulates
brisk growth of plankton that ultimately leads to depletion of
oxygen in the water. Similarly, dumping of 9 million metric tons
of sewage sludge annually off the New York/New Jersey shore has
resulted in deoxygenation of 4,700 square miles of formerly productive
offshore bottom communities (12).
Blooms of toxic phytoplanktons and red tides have increased in
frequency over the last two decades, and may be linked to coastal
pollution. For example, a recent study traced stormwater runoff
from the drainage into Santa Monica Bay, California which carried
with it suspended particulates, nutrients, heavy metals, and toxics.
The researchers concluded that effects of the stormwater runoff
often resulted in dinoflagellate (red tide) blooms following storms.
Such events not only cause mass mortality among some fish species,
but can result in marine mammal deaths and pose a threat to human
Water treatment technology has advanced in recent years, leading
to substantial improvements in those areas where the new technology
is applied. However, many developing countries cannot afford to
implement these new technologies, and population growth in coastal
cities has continued to overwhelm existing waste treatment systems.
Worldwide, substantially more study is needed on the effects
of pollution on the marine environment, which will facilitate
understanding of the complex problems, their myriad potential
causes, and ways in which damaged ecosystems can be restored.
Introduction of Alien Species
Alien species are plants and animals that naturally occur in one
part of the world, where their natural predators, diseases, and
interactions within the ecosystem keep their populations in balance,
but that are artificially introduced into a new ecosystem where
those controls may not exist. In many instances, the new environment
is not hospitable to the introduced species, and it fails to thrive
there. However, in many cases, the new species has thrived, outcompeting
the naturally occurring species, upsetting, and in some instances
devastating, the local ecosystem.
On land, some of the most devastating alien species introductions
have occurred by accidental air transport of the non-native species.
In the ocean, the primary mechanism of alien species introduction
has been in the ballast water of shipping vessels. Ships fill
and empty their ballast tanks in order to maintain stability in
the water. Anything living in that water can easily get sucked
in, and discharged elsewhere when the ship's ballast tanks are
emptied. Scientists estimate that as many as 3,000 alien species
per day are transported in ships around the world (23).
Alien species are more of a concern in coastal waters than in
the open ocean, as coastal zones are more likely to be biologically
and ecologically distinctive and disconnected. Alien species are
also more likely to be problematic where bodies of water are not
naturally connected to one another. For example, transport of
a species from the Indian Ocean to the Pacific is unlikely to
have significant impact, as the two oceans are already connected.
Transport of a species from tropical regions of the Atlantic to
the Pacific would be more likely to have a disruptive influence,
because there is little naturally occurring exchange between them
The impact of alien species has increased dramatically in recent
decades because of a global increase in shipping. Depletion of
local resources (including grain, wood, fuels, materials for consumer
goods, etc.) in many areas of the world has outstripped global
population growth rates. Places that were formerly self-reliant
now depend on imports to meet their requirements. Driven in some
cases by local depletion and in others by affluence, the needs
of Earth's current human population are largely met by moving
products and resources around the globe (23).
This increase in shipping has resulted in a corresponding increase
in development of port facilities and risk of oil spills, as discussed
in previous sections. But it has also brought with it a huge increase
in the introduction of marine alien species into ecosystems incapable
of coping with them, as ships pick up species from one part of
the world in their ballast water, and release them in new areas,
where those species had never previously occurred.
For example, Mnemiopsis leidyi, a comb jellyfish native to temperate
and tropical western Atlantic bays and coastal waters, was first
observed in the Black Sea in 1982, and is believed to have been
introduced in ships' ballast water. Since it feeds on zooplankton
including eggs and larvae of commercial fishes, it has been linked
to a decline of Black Sea sprat and anchovy. Some have proposed
introduction of another alien species, butterfish, into the Black
Sea to control the mnemiopsis population. However, many scientists
fear that such a plan would create new and potentially more severe
The Green crab, Carcinus maenas, is a European native which was
introduced and became established on the Atlantic Coast of North
America more than a century ago, and now ranges from Nova Scotia
to New Jersey. In recent years, the green crab has been introduced
to the waters off South Africa, southern Australia and (starting
in 1989 or '90) the US Pacific Coast.
Green crabs are voracious predators of invertebrates such as
clams, mussels, oysters and smaller crabs. They threaten the large
and important fisheries for mollusks and Dungeness crabs, as well
as large numbers of noncommercial invertebrate species, but are
too small to be themselves of commercial interest as seafood for
humans. There is active discussion of releasing biocontrols, ranging
from parasitic barnacles to microorganisms, to slow or stop the
advance and proliferation of the green crab. However, there is
concern regarding the possible hazards of introducing yet another
alien species into those waters (c).
San Francisco Bay offers one example of an ecosystem that has
been overwhelmed by numerous alien species introductions. Today,
there are more that 200 different alien species living in San
Francisco Bay, severely impacting on native species, and the overall
functioning of the ecosystem. Although the alien species have
not completely eliminated native species, the character and natural
processes of the Bay have been substantially altered (d).
In addition to changing the functioning of marine ecosystems,
alien species can also affect human health. Zebra mussels, an
introduced species which has thrived in the Great Lakes, have
caused problems ranging from disrupting native species to clogging
pipes, but have also had the positive effect of filtering toxins
and various pollutants from the water. More recently, another
alien species, the round goby, has arrived, and has proved a voracious
consumer of zebra mussels. The problem is that popular game fish
eat the gobies, thereby ingesting highly concentrated amounts
of the toxic substances that the gobies accumulated from the zebra
mussels, and passing them on to the humans that eat them (d).
Failure to understand the complex relationships between species
can have serious consequences not just for natural systems, but
human health as well.
Global Climate Change
As the world's human population has increased, so has use of fossil
fuels and other pollutants that are known to contribute to global
climate change. Between 1950 and 1987, annual global carbon dioxide
emissions from anthropogenic sources increased from 1,638 million
metric tons to 5,650 million metric tons (12). Although significant
climate changes have occurred naturally throughout the Earth's
history, most climate scientists agree humans' activities have
accelerated the rate at which climate change is now occurring.
The concern expressed by some ecological scientists is that species
and ecosystems that may be capable of adapting to slow climate
change may be unable to adapt quickly enough to survive. The implications
for humankind are profound.
Effects of climate change on marine ecosystems have already been
observed, and these effects appear to be accelerating. Melting
of glaciers and polar ice caps, and increased water temperature,
is causing the sea level to rise, threatening coral reefs, coastal
mangroves, salt marshes, and other coastal and marine ecosystems.
Estimates of projected sea level rise by the year 2100 range from
four inches to eleven feet. The Intergovernmental Panel on Climate
Change predicts a 26 inch rise in sea level by 2100, which suggests
rates three to six times higher than those seen over the past
century. Some experts believe these projections may be too conservative.
Rising sea levels threaten humans as well as wildlife. Based on
the above projections, Bangladesh would lose 12 to 28% of its
total land area within the next century, and the island nation
of Maldives would be entirely submerged (12).
While climate change affects water temperature and warm-water
currents, melting of polar ice and changes in rain patterns which
accompany climate change also affect the levels and patterns of
salinity in marine waters. Many scientists believe that rather
than a slow gradual shift in ocean systems and associated atmospheric
patterns, a sudden, global reorganization of ocean-atmospheric
patterns is likely to occur once some threshold point has been
crossed. It is difficult to predict what the effects on marine
ecosystems and species will be. Some could benefit, others perish.
Changes in growth, migratory behavior, competition, and other
interactions between species would likely be profound (12).
Global climate change can have profound effects on the oceans.
But the reverse is also true. The ocean plays a vital role in
regulating weather patterns, generating oxygen, and removing carbon
dioxide from the atmosphere. Thus, the health of the oceans can
have a profound impact on the nature and extent of climate change.
Microscopic life in the oceans helps reduce greenhouse gasses
responsible for climate change by controlling the amount of carbon
dioxide in the atmosphere. Phytoplankton living in the upper 100
meters of the water column take carbon out of solution, and when
they die, they sink to the bottom, carrying the carbon with them.
Photosynthesis and decay essentially pump carbon from the surface
into the deep ocean. Without this biological process, the carbon
dioxide in the deep sea would begin to rise to the surface and
enter the atmosphere, potentially doubling or tripling the level
of carbon dioxide in the atmosphere within only a few centuries.
Human activities that reduce the effectiveness of this process
could therefore contribute further to global climate change (12).
Population growth affects the health of the world's oceans via
complex pathways. A multitude of factors which interact with one
another appear to be contributing to degradation of marine ecosystems
and loss of biodiversity. There is much scientists still need
to learn about the causes and effects at work, and what can be
done to reverse damage which has already occurred. Human population
contributes to the amount and frequency of activities which may
have long-term negative effects on the marine environment, and
drives ever-increasing pressure on the Earth's finite resources.
Many scientists worry that changes in ocean ecosystems brought
about by overexploitation, physical alteration, pollution, introduction
of alien species, and global climate change, are outpacing efforts
even to study them, let alone ameliorate their effects. The concern
within the scientific community that the oceans are in trouble
has led more than 1000 marine scientists and conservation biologists
to sign the Troubled Waters Statement (9). The statement, a project
of the Marine Conservation Biology Institute, was developed to
demonstrate to policy makers and the general public that there
is a strong scientific basis for concerns about the health of
the oceans, and that those who are in the best position to know
objectively what the facts are believe the oceans are in trouble.
Although population plays a role in the problems discussed here,
it may be the factor least amenable to change in the short term.
While efforts to slow or reverse population growth through political
and social change are essential, the impact humans are currently
having on the oceans can be addressed in other ways. Steps that
can be taken to slow the effects of human activities on marine
- Policies to support sustainable taking of living resources and
to discourage unsustainable practices.
- Policies and new methods to limit pollution.
- Creation and management of marine protected areas.
- Communication to facilitate understanding of how preserving
the health of the oceans is in humankind's best interests.
- Development of an ocean ethic which emphasizes long-term health
and benefit to humankind over short-term profits.
Even if all of these are effectively implemented, however, the
problem of overpopulation will remain, and will continue to be
reflected in human effects on marine life and systems.
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1. American Association for the Advancement of Science, 1997:
Science Magazine, Vol 277 (magazine issue devoted to human dominated
2. American Oceans Campaign, 1997: Fisheries in Decline. Internet:
3. Earle, S. A., 1995: Sea Change: A Message of the Oceans. New
York: G.P. Putnam's Sons.
4. Gray's Reef and Stellwagen Bank National Marine Sanctuaries,
1996: The Northern Right Whale: From Whaling to Watching. Savannah,
GA: National Oceanic and Atmospheric Administration.
5. Hinrichson, D., 1996. Coasts in Crisis. Issues in Science
and Technology, Summer, 1996, pp. 39-47.
6. Jackson, D. Z., 1997. A fish story that's dead serious. August
15, 1997, The Boston Globe.
7. Linden, Eugene, 1993: Megacities. January 11, 1993, Time,
8. Marine Conservation Biology Institute, 1996. Bottom Trawling:
The Unseen Worldwide Plowing of the Seabed. Internet: http:www.mcbi.org/emerg.html
9. Marine Conservation Biology Institute, 1997. Troubled Waters:
A Call for Action. Internet: http:www.mcbi.org/trouble1.html
10. Mooney-Seus, M. L. & Stone, G. S., 1996: The Forgotten
Giants. Joint publication of the New England Aquarium and the
Ocean Wildlife Campaign.
11. Miller, M.C. & Cogan, J. Eds., 1996: Coastal Zone 97:
The Next 25 Years. Washington D.C.: Coastal Zone 97.
12. Norse, E. A., Ed., 1993: Global Marine Biological Diversity:
A Strategy for Building Conservation into Decision Making. Washington
D.C.: Island Press.
13. The Oceanography Society, 1996: Oceanography: Serving Ocean
Science and its Applications Vol 9, No 1(magazine issue devoted
to marine biodiveristy).
14. Population & Environment Program: Population Action International,
1995: Catching the Limit: Population and the Decline of Fisheries
(informational poster). Washington D.C.: Population Action International.
15. President's Council on Environmental Quality, 1990: Environmental
Quality 1970-1995: Twenty-Fifth Annual Report. Washington D.C.:
President's Council on Environmental Quality.
16. President's Council on Sustainable Development, 1996: Sustainable
America: A new Consensus. Washington D.C.: The President's Council
on Sustainable Development.
17. Safina, C., 1998: Song for the Blue Ocean. New York: Henry
Holt & Company.
18. Starr, C., 1997: Fish dying out, expert warns. August 28,
1997, The Cincinnati Post.
19. Stevens, W. K., 1994: Feeding a Booming Population Without
Destroying the Planet. April 5, 1994, New York Times.
20. World Resources Institute, 1993: World Resources: A guide
to the Global Environment. New York: Oxford University Press.
21. World Resources Institute, 1997: Marine Fishing Trends: Troubled
Waters Ahead. Internet: http://www.wri.org/wri/wr-96-97/wa_txt2.html
22. World Resources Institute, 1997: Marine Biodiversity. Internet:
23. World Resources Institute, 1997: Pressures on Marine Biodiversity.
24. World Resources Institute, 1997: Threats to Coastal Ecosystems.
a) Personal Communication, Alyson Simmons, Educational Program
Director, Florida Keys National Marine Sanctuary
b) Personal Communication, Dr. Sylvia A. Earle, CEO, Deep Ocean
Exploration & Research
c) Personal Communication, Dr. Elliott Norse, President, Marine
Conservation Biology Institute
d) The Ocean Report, a SeaWeb project of the Pew Charitable Trusts.
National Public Radio broadcasts of 4/16/97 and 7/8/97.
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of Selected Terms
Anthropogenic: Caused by humans, whether intentionally
Aquaculture: The farming of marine organisms for human
Biocontrols: Use of a living organism, whether plant,
animal, or microorganism to control the population of an undesired
Biodiversity: The variety of different species in an
ecosystem, genetic variation within a population of a species,
and variety of kinds of ecosystems. Greater biodiversity makes
species and systems more resilient, while loss of biodiversity
weakens them, making them more vulnerable to extinction.
Biosphere: All of the combined regions of the planet
which support self-sustaining ecosystems. The biosphere extends
above and below the surface of the Earth, wherever there are living
Bottom Trawling: A fishing technique involving dragging
heavy nets across the sea floor to catch bottom-dwelling fish.
Results in severe changes to the sea floor, a high rate of bycatch,
and loss of biodiversity.
Bycatch: Living organisms caught and/or killed by fishermen
which are not what they intended to catch. Bycatch includes other
species of fish or shellfish, marine mammals, birds, turtles,
and specimens of the target species which are below the legal
size or otherwise prohibited.
Coastal Zone: The area of land within 100 km the ocean
and the area of ocean near the land. Coastal waters support critical
habitat and nurseries for a vast number of important marine species.
Continental Shelf: A relatively shallow, submerged portion
of a continent, extending to a point of steep descent to the ocean
Coral Reef: A marine ridge or mound comprised primarily
of coral, together with algal and mineral components, which forms
the foundation for a biologically rich and diverse ecosystem.
Critical Habitat: Living areas that are crucial for a
species' survival based upon their unique needs. Some species
are less able to adapt than others to changes in their habitat,
and thus more vulnerable to the effects of human activity.
Dinoflagellate: Microscopic marine organisms which have
whirling whiplike appendages, and which form one of the chief
constituents of plankton.
Dredging: Digging up the sea floor for such purposes
as extending beaches or making harbors deeper.
Ecosystem: An ecological community, including the biological
inhabitants, and the environment in which they live, and encompassing
the interactions among them which permit the system to function
and to sustain life.
Estuary: The area where a river meets the ocean, which
may be a widening of the river where its current is met by the
tides, or an arm of the sea which extends inland.
Genetic Diversity: The total number of genes for a given
breeding population makes up its gene pool. A large gene pool
is genetically diverse, and therefore more likely to be healthy
Greenhouse Gasses: Certain gases, such as carbon dioxide,
which serve to hold heat in closer to the Earth's surface. Without
any greenhouse gases, the Earth's surface would be about 33 degrees
centigrade colder than it is. However, with an increase in greenhouse
gases in the atmosphere, the temperatures increase.
Mangrove Forest: Dense coastal thickets of tropical evergreen
trees and shrubs of the genus Rhizophora, or Avicennia, or similar
species, which grow along tidal shores throughout tropical regions
of the world, and which provide the foundation for a biologically
diverse and ecologically important ecosystem.
Phytoplankton: Minute floating aquatic plants.
Sustainable/Unsustainable: When an activity can be done
indefinitely without any increase in it's effects, it can be considered
sustainable. If the activity is done at a rate or level which
is faster or greater than nature's capacity to recover from it,
the activity is unsustainable. Unsustainable practices are like
squandering the capital in your savings account instead of living
on the interest and keeping the capital intact, killing the proverbial
"goose that laid the golden egg."
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