It Comes Down to the Coasts
by Peter Weber, reprinted from World Watch, vol. 7 No. 2, with permission
Along the seams of the earth where land meets sea, biological productivity
is much higher than for the rest of the planet's surface. If the coasts
are to continue serving their essential ecological and economic functions,
we will have to begin altering our patterns of human settlement and development.
hat is a view of the ocean worth? The price of a night
at an expensive hotel, or the purchase of a beachfront bungalow? Enduring
a biting winter wind, or a beach-bound traffic jam on a sultry day in August?
For many, the answer is: whatever it takes. Every year, half of the world's
vacationers head for the sea.
But for many more people, being close to the shore is
worth something more than an annual pilgrimage. It is worth the cost of
leaving better-paying jobs, or ancestral ties, or friends - and moving their
homes to the coast. Fully half the world's people live within 50 miles or
so of saltwater. And their ranks are growing. In 30 years, the same number
of people as are now on earth - some 5.5 billion - are expected to live
in the coastal zone.
What is the attraction? The meeting of land and sea
works a kind of magic that is more powerful than that of just scenic beauty.
The soil on the coastal plain, laid down when the land was covered by the
ocean, and subsequently replenished by sediments washed down from the mountains,
tends to be particularly fertile. About 2 percent of the world's agricultural
land, including some of its most intensively and productively cultivated
land, was actually taken from the sea by people.
Offshore, the same nutrients promote the growth of aquatic
plants, which in turn feed fish that now provide humankind's largest single
source of animal protein-larger, even, than beef or chicken. The world's
primary fishing grounds are in these fertile coastal waters, from which
90 percent of the marine catch is taken. Farming and fishing are major coastal
industries that employ hundreds of millions of people worldwide.
Coastal dwellers can also make a good living from international
trade, 80 percent of which is carried by ship. That's one reason why nine
of the world's 10 largest cities and 33 of the top 50 are near the coasts.
And of course there are the vacationers bringing their portion of the $1.9
trillion annually spent on tourism worldwide. Although there are no estimates
for coastal tourism alone, the Madrid-based World Tourism Organization estimates
that tourism accounts for nearly one-tenth of the global economic output
and is one of the fastest growing industries. The attraction of the coasts
is as much economic as aesthetic.
It's not surprising, then, that the narrow ribbons of
land and water that outline the world's continents and islands are widely
used as development zones. The phenomenon is nowhere more vividly illustrated
than in The Netherlands, whose crowded populace lives with the sea literally
in its back yard. In fact, one-third of The Netherlands is land that used
to be under the North Sea or its tributaries; because coastal land is so
valuable to the Dutch, they have been diking and draining it continuously
for over a thousand years. Their sea-hugging cities are now thriving centers
of commerce and culture, and their farms are some of the most productive
in the world.
All this activity may churn out money, but it is also
churning up the coasts - as the Dutch have become acutely aware in recent
decades. Draining wetlands has reduced the natural habitat for wildlife
and has driven the Dutch national symbol, the stork, from the country.
But the problem is more than just a few endangered species.
By choosing to concentrate its swelling population along the coasts, humanity
is locating the ecological damage of its activities precisely where the
world's most productive ecosystems are concentrated. The coastal zone, extending
from the beginning of the coastal plain to the end of the continental shelf,
accounts for only eight percent of the world's surface area, but hosts 26
percent of the earth's primary (plant) productivity, the world's major spawning
and nursery grounds, and one of the earth's most diverse ecosystems, the
coral reefs. As a result, coastal areas, which are approximately twice as
productive on average as the inland areas, suffer roughly nine times more
damage because of the number of people living there.
Hazards at the crossroads
Having chosen to live where land meets sea, humanity
has greatly increased the difficulty of achieving a stable relationship
with the Earth's environment. The intersection between human and biological
activity has already scarred the coastal landscape by altering and destroying
large portions of some of its most fertile habitat.
Not all coastal habitat is highly productive; about
half of the world's 440,000 kilometers of coastline are lined by cliffs
and ice, and another 20 percent are beaches, which have relatively low biological
activity. However, wetlands and estuaries, where rivers turn brackish as
they enter the sea, are among the most productive of all ecosystems. There,
nutrients from land feed plant growth so abundant that mangrove forests,
for instance, which cover only 0.4 percent of the world's surface area,
account for 2.3 percent of plant productivity. That fecundity makes mangroves,
other coastal wetlands, and estuaries particularly important as nurseries
for marine species. Some two-thirds of all commercially caught fish spend
their first and most vulnerable stages in estuaries and wetlands, and many
more species go to these coastal ecosystems to feed.
These are also some of the most endangered ecosystems
in the world. Estuaries are particularly vulnerable because they are naturally
sheltered harbors, and therefore tend to be heavily used and polluted. Wetlands
have traditionally been regarded as wasteland, and therefore are targets
for city expansion. All over the world, there are coastal cities that have
degraded nearby estuaries and wetlands through the combined effects of direct
habitat destruction and pollution. Commercially burgeoning Singapore, for
example, has removed almost all of its mangrove wetlands and reduced offshore
water visibility from eight meters prior to 1960 to an average three meters
in 1992. San Francisco Bay, the largest estuary in the western United States,
has lost 60 percent of its water area to land reclamation over the past
It is agriculture, however, not urbanization, that causes
the most extensive destruction. The Dutch impound coastal wetlands with
dikes, then pump them dry with windmills, primarily for the fertile farmland.
The Chinese have been draining coastal wetlands for the rich soils they
yield for 6,000 years. The densely populated delta country of Bangladesh
has impounded at least 30,000 square kilometers of wetland for agriculture;
it is no coincidence that Bangladesh has the world's highest population
density for a mainland country, as well as the largest area of impounded
Other causes of extensive coastal habitat destruction
include the rapidly expanding fish farming industry, timber extraction,
and civil engineering projects that alter the flow of sediments and fresh
water. The wetlands at the mouth of the Mississippi River are eroding away
at a rate of 150 square kilometers per year, largely due to flood control
and channeling projects in the delta and upstream. Worldwide, about half
of all salt marshes and mangrove swamps have been cleared, drained, diked,
or filled, and few estuaries remain unpolluted or unaltered.
Offshore, coral reefs, kelp forests, sea grass beds,
and other shallow water habitats are endangered by the combination of direct
destruction and pollution from land. Coral reefs are of particular concern.
They line more than 100,000 kilometers of coast and harbor a large portion
of the coasts' biological wealth. Unfortunately, they are highly vulnerable
to changes in their environment. If the normally clear tropical waters they
form in are clouded by pollutants, for example, the corals can't photosynthesize
to produce their food. They also recover slowly when damaged. Other offshore
habitats, likewise, suffer from such habitat degradation. The pollution
and harbor development off Singapore, for instance, has degraded the majority
of the sea grass beds and all but five percent of the coral reefs.
The unique ecology of coral reefs makes them one of
the world's most diverse ecosystems, second in density of unique species
only to tropical rain forests; thus the widespread damage to these reefs
constitutes a major blow to the Earth's overall biological diversity. Yet,
5 to 10 percent of the planet's coral reefs have essentially been ruined
by pollution and direct destruction, and another 30 percent could be lost
in the next 10 to 20 years. The most graphic examples are the extensive
portions of reef that have been mined for construction materials in places
like southern India and Sri Lanka, and the damage caused by fishers using
explosives to kill and catch fish. But globally, pollution from burgeoning
developments onshore is the more extensive and intractable threat to these
and other coastal habitats.
The demographic squeeze
Without closer attention to the management and protection
of these coastal ecosystems, the destruction is bound to accelerate. Because
of steady coastward migration, coastal populations-and the environmental
pressures they bring - may be growing even faster than the global population,
which is climbing by some 90 million people a year.
One of the forces driving the trend is rural poverty.
Like a pied piper, the promise of employment in cities draws people from
depressed agricultural areas. The United Nations estimates that 20 to 30
million of the world's poorest people annually migrate from rural to urban
areas, especially to Third World mega-cities, which are usually on the coasts.
Rural coastal populations may also be increasing for similar reasons. In
the Philippines, the coastal population is growing faster than that of the
rest of the country in part because people who give up on farming often
move to coastal areas to try fishing. While land is scarce, open access
to fishing grounds gives poor people at least the hope of making a living.
In China, the coastal population may be increasing by
10 percent or more per year, though the country's overall growth rate is
only 1.2 percent. Already the population density along the China coast is
three times as high as the national average, and this region accounts for
70 percent of the country's gross national product. While the economic success
along the coast will inevitably attract more Chinese, the government is
encouraging this coastward migration by placing special economic development
In Southeast Asia, where marine biodiversity is particularly
high, more than two-thirds of the population lives within the coastal zone.
Coastal populations are also particularly high in southern Asia, Europe,
southeastern Africa, and portions of North and South America. And as the
global trend of rural flight and urbanization progresses, the challenge
to protect the world's coasts will become more severe.
More than coastal living
As if this pattern of human habitation weren't damaging
enough, the thin ribbons of coast are also subject to devastating environmental
assaults from both far inland and out at sea. Pollution from human activity
outside of the coastal zone funnels into estuaries and coastal waters, while
in an almost mirror image, the impacts of fishing and shipping become more
concentrated closer to shore.
A surprising proportion of the pollutants entering coastal
waters originates not from the adjacent coastal land but from more distant
sources. Of the polluting nutrients, about half come from inland. In the
eastern United States, for instance, the Chesapeake Bay has been overwhelmed
by nutrients from inland sources. Farms contribute one-third and air pollution
another one-quarter of the nitrogen pollution that has caused eutrophication,
algal blooms, and oxygen depletion in this estuary - once one of the most
productive in the world. The oyster catch in the Chesapeake has fallen from
20,000 tons in the 1950s to under 3,000 tons in the late 1980s, at least
partly as a result of this pollution.
In a study of samples from 42 of the world's major rivers,
Jonathan J. Cole and his colleagues at the Institute of Ecosystem Studies
at the New York Botanical Garden found that the level of pollution correlates
uncannily with the level of human activity in the watershed. The Rhine,
for example, has 10 times the population density of the Mississippi, and
dumps 10 times more nutrients into the sea, even though the Mississippi
drains an area 14 times as large.
About one-third of the pollutants entering the marine
environment come from air emissions, a large portion of which settle into
coastal waters. For many heavy metals and volatile organic chemicals, air
is the primary route to the sea. In the North Sea, about a quarter of the
pollution, including the majority of PCBs and other chlorinated organic
chemicals, comes from the air. In the Persian Gulf, the four to 12 million
barrels of oil that the Iraqi army deliberately spilled during the 1991
Gulf War turned out to be only part of the total amount of oil estimated
to have entered the Gulf as a result of the war. Another four to five million
barrels are thought to have been carried into the Gulf by oil-laden smoke.
Worldwide, about 10 percent of the oil that reaches the oceans is airborne.
Ironically, human industries and settlements are choking
coastal waters with the very rivers that make these waters productive. The
excess nutrients, sediments, pathogens, and persistent toxins come mostly
from land-based sources. Even oil pollution, which is typically associated
with accidents at sea such as that of the Exxon Valdez, is as likely to
have flowed into the water directly from a car or factory on land as from
a barge or boat.
On the ocean side of the coastal zone, overfishing has
depleted some of the world's major fish stocks, along with the health of
their ecosystems. There is a growing crisis in the world fisheries, as epitomized
by the collapse of North Atlantic cod stocks off Canada. Although pollution
and habitat destruction have played a role in this crisis, the main problem
is simply that the capacity of the fishing industry - in numbers of people
and in the efficiency of their high-tech equipment - has grown too large
for the regenerative capacity of the oceans. Of the world's 17 major fishing
grounds, all of which are primarily coastal, every one has been fished to
its limits or beyond, according to the United Nations Food and Agriculture
Organization (FAO), which tracks global fishing trends. Nine are now in
serious decline because of overfishing.
As high-tech factory boats and traditional fishers alike
have extracted larger and larger proportions of the biomass from coastal
waters, whole ecosystems have begun to break down. In the Shetland Islands,
Arctic terns, puffins, and other nesting birds failed to breed in the mid-
and late 1980s, apparently due to overfishing of the sand eel, a small shoaling
fish caught for fish meal and oil. The birds normally feed young sand eels
to their chicks, but the fish's population declined with the commercial
catch, which peaked at 56,000 tons in 1982 and then plunged to 4,800 tons
in 1988. In a similar disaster, off the coast of Peru, guano birds abandoned
their young when the Peruvian anchovy fishery collapsed. In Kenya, researchers
found that heavy fishing of triggerfish on coral reefs allowed the proliferation
of rock-boring sea urchins, which were endangering the entire ecosystem.
[End of Part I. Part II will appear in the October issue of Earth
Peter Weber is a research associate at the Worldwatch Institute. He is author
of Worldwatch Paper 116, Abandoned Seas: Reversing the Decline of the Oceans
(1993), and co-author of State of the World 1994. This article based on
field research in the Netherlands, as well as on his previous work on the