Saving the coral reefs.

Coral reefs are arguably the world's most beautiful habitats. But reefs are vulnerable to climate change, pollution, and abuse by humans, making them among the most threatened ecosystems on the planet.

Coral reefs are renowned as underwater marvels of fluorescent colors, fantastic shapes,

and improbable creatures. Delicate purple sea fans, blood-red sponges, spiny pufferfish, poisonous scorpionfish, giant clams, yellow-lip snakes, and giant manta rays are just a small sample of the fascinating residents that awe visitors from the terrestrial realm. Iridescent fish dart between the intricate coral formations. For their beauty alone, reefs rank as one of the greatest treasures of the planet.

Coral reefs are also among the most endangered ecosystems on Earth. Human beings have damaged or destroyed significant amounts of reef off the coasts of 93 countries, according to a study in the mid-1980s by the World Conservation Union and the U.N. Environment Programme (UNEP).

Silt from deforested lands and pollution from crowded coastlines choke them, and overuse by coral miners, fishers, and even tourists deplete and destroy them. At current rates of destruction, much of the world's reefs could be destroyed in the next 50 years.

Unmined Riches

Concern over the decline of these tropical ecosystems, however, is not solely focused on their magical appearance. Coral reefs are among the most biologically diverse ecosystems on Earth. Covering only 0.17% of the ocean floor--an area the size of Texas--coral reefs are home to perhaps one-fourth of all marine species, earning them the title "the tropical rain forests of the oceans."

Globally, coral reefs are thought to be second only to tropical rain forests in terms of the number of species they contain. Like the rain forests, reefs hold considerable untapped potential to contribute to science, particularly medicine. Kainic acid, collected from reef organisms in Japan and Taiwan, is used as a diagnostic chemical to investigate Huntington's chorea, a rare but fatal disease of the nervous system. Other reef organisms produce chemicals useful for cancer and AIDS research.

Corals themselves produce a natural sunscreen, which chemists are developing for the Australian market, and their porous limestone skeletons are promising for bone grafts in humans.

For the 109 countries whose shores are lined with more than 100,000 kilometers of reefs, they provide immeasurable service by protecting coastal lands from the erosive forces of the sea. For many local people reefs are saltwater supermarkets of food and raw materials. Pacific Islanders obtain up to 90% of their animal protein from reef fish, and people in Southeast Asia, the Caribbean, and parts of southern Asia and eastern Africa also derive a substantial portion of their protein from reef fish. Worldwide, reefs yield approximately one-tenth of all fish caught for human consumption, or 4 to 8 million tons annually.

Reef Ecology

Among the many inhabitants of tropical reefs, corals have a key role. The warm, clear waters where reefs form are deficient in nutrients that would typically allow marine life to flourish. Corals overcome this deficiency through a clever bit of evolution. The coral animal (a sedentary relative of jellyfish) takes advantage of the abundant sunlight in the clear waters by harnessing microscopic algae. The algae live in the corals' translucent tissues and provide them with food and oxygen from photosynthesis. The corals in turn recycle carbon dioxide and other materials for the algae to use, making efficient use of scarce nutrients.

This symbiotic relationship between corals and algae is sensitive to such changes in the environment as cloudy waters or extreme temperatures. The stress on the corals can cause them to expel their algae, a phenomenon known as bleaching. With the algae gone, the white limestone of the coral skeleton is visible, and the corals die if the stress is not relieved.

Dead corals lead to the death of the reef. The corals provide some food to reef organisms, but more importantly their limestone formations stabilize and add to the complex structure that allows a wide variety of species to thrive. Without corals, the reef erodes and the wide variety of organisms declines.

The other species on the reef likewise contribute to the health of the ecosystem. Some of the fish clean off the seaweed that would overgrow the corals, others clean bacteria from bigger fish, and still others help control coral predators. The chains of interdependence between corals and the species that find shelter in the reef are like a self-perpetuating immune system. If one link is disrupted, the health and diversity of the whole ecosystem can decline. For example, one square kilometer of a healthy reef can meet the ongoing protein needs of hundreds of people, but if degraded it will support only a fraction of that number.

Reefs on the Rocks

Humans have directly or indirectly caused the death of 5%-10% of the world's living reefs, according to marine biologist Clive Wilkinson of the Australian Institute of Marine Science. At current rates of destruction, another 60% of the reefs could be lost in the next 20-40 years, he believes. And these estimates do not take into account potential effects of global warming and ozone depletion.

Wilkinson's rough assessment plots the general trend that reef scientists have been documenting for more than two decades. The picture he paints is not an encouraging one: Only reefs in remote regions are generally healthy. Areas with tracts of particularly devastated reefs include Japan, Taiwan, the Philippines, Indonesia, Singapore, Sri Lanka, and India in Asia; Kenya, Tanzania, Mozambique, and Madagascar in Africa; and the Dominican Republic, Haiti, Cuba, Jamaica, Trinidad and Tobago, and Florida in the Americas. The causes of degradation vary, but dense coastal populations and heavy coastal development are factors shared by all.

Topping a long list of abuses against reefs is sedimentation from logging, farming, mining, dredging, and other coastal activities. Sediments that wash over reefs have a number of negative effects on corals. The initial plume blocks out sunlight, reducing photosynthesis among the algae and therefore the quantity of energy available to the coral polyps. Sediments also impede coral larvae from forming new colonies on the reef.

Deforestation is the most common source of sediments, and mangrove clearing is the most important type of forest loss. Mangroves, which form along coastlines, trap soils that would otherwise wash into the coastal waters onto reefs. When trees are cleared, they can no longer play this protective role. In the watershed of Bacuit Bay in the Philippines, logging increased erosion into the bay by more than 200 times. In 1985, the first year of logging there, 5% of the corals in the bay died.

Population's Impacts on Reefs

More than half the world's population now live in coastal regions, and, as human numbers continue to grow, this proportion is expected to increase. Already, more than 70% of the people in parts of Southeast Asia live near the coast. As populations continue to grow, both land clearing and development will increase.

Only reefs that are relatively untouched by human activity are in good shape. Among the better-off ones, Australia's Great Barrier Reef is more than 260 kilometers from shore at its most distant point. Belize, in Central America, also has a generally well-preserved barrier reef due to the country's low population density. Elsewhere, reefs are usually healthy along sparsely populated islands--particularly atolls, since soil runoff is limited.

But people are steadily encroaching on reefs. In the Middle East, the lush reefs of the Red Sea contrast starkly with the surrounding desert landscapes. Until recently, this isolation had been the reefs' salvation: Settlements along these bodies of water have been scarce, and people living there have not used the reefs extensively for fishing or raw materials.

With the oil boom, however, increased commerce has led to the degradation of some of the region's reefs. Oil spills can kill shallow corals outright, interrupt reproduction and metabolism, and smother corals if heavy tars settle. Even worse, detergents used to disperse spills are acutely toxic to corals, although new methods have been developed that avoid this problem. Shipping is another serious threat to the Middle East reefs. In one case, a ship "virtually eliminated" all life on 500 square meters of reef when it ran aground and released several hundred tons of phosphate.

Exploited Ecosystems

The many assets of reefs are also the source of their decline. They attract people in pursuit of food, exotic species, gift-shop corals, and limestone for building materials, as well as tourists and tourist complexes. Although less insidious than sediment and other pollutants, overexploitation is a pervasive problem for reefs.

Overfishing and other strains can create a cycle of degradation. As incomes fall, fishers are forced to pursue other sources of income, some of which can be destructive to reefs. Some fishers in the Philippines earn extra income by collecting turtles, mother of pearl, and other prized reef species that will fetch high prices in international markets. These species in particular are over-harvested. And giant clams, once common in the reefs of Southeast Asia, have been eliminated from reef after reef because their meat is a delicacy in the region. Other coveted species could suffer a similar fate.

Corals themselves are gathered and sold as part of the international trade of reef products. Worldwide, some 1.5 million kilograms of coral are harvested annually. A major destination for this coral and for tropical aquarium fish is the United States, which accounts for more than a third of the world demand for both products. Live corals for elaborate home saltwater aquariums are a small but growing portion of this market. Florida was a major supplier of corals until 1989, when the state shut the industry down to protect its reefs. In 1989, the United States also banned the import of coral from the Philippines, where export is illegal, but supplies continue to enter the United States from Indonesia, Singapore, and illicit channels.

Reefs are also mined for building materials. In Sri Lanka and India, entire sections of reef have been removed to produce cement. |Sri Lanka banned coral mining in early 1992.~ Small coral islands in the Philippines and Indonesia have likewise been mined out of existence. People in island regions especially use the reef's limestone for construction, either because they have no other source of rock or because an island's base rock is volcanic, which is not strong or durable.

Tourism is often cited as a motivation for countries to protect their reefs from these various forms of destruction, yet the boom in this industry is also contributing to the degradation of reefs in some areas. Tourists and divers walk on the reef, killing coral polyps. Reckless divers also kick up sediments and break off pieces of corals. Although single incidents may be minor, the cumulative effect in heavily visited tourist centers, like the Florida Keys, can be devastating.

Even if tourists stay out of the water, resorts built to serve them contribute to the degradation of coastal water quality. Beachfront development increases sedimentation of reefs, and hotels generally pipe their sewage and wastewater directly into the ocean, polluting nearby reefs. Entrepreneurs harvest corals and other souvenirs for local sale.

The Changing Climate for Corals

In addition to the immediate threats of pollution and overuse, reefs will have to weather the future consequences of two forms of global environmental change: (1) the gradual warming of the earth due to the accumulation of carbon dioxide and other heat-trapping gases in the atmosphere and (2) the rising intensity of the sun's harmful ultraviolet rays due to the destruction of the stratospheric ozone layer.

Climatologists project that atmospheric concentrations of "greenhouse gases" will double within the next five decades. The subsequent warming is likely to cause a number of global changes. As the oceans warm and the polar ice caps melt, sea level is expected to rise some six centimeters per decade. The changing climate is predicted to alter weather patterns and to lead to stronger storms. The combination of differential warming of the oceans and changed weather patterns could in turn shift the ocean's normally stable circulation patterns.

Such changes are likely to harm coral reefs. Higher atmospheric carbon-dioxide levels alone could chemically inhibit coral-building by the polyps. Stronger, more-frequent storms would increasingly damage reefs. Major changes in ocean circulation would imperil reefs where cold or nutrient-laden waters replace the more-hospitable waters that now bathe them.

Coral bleaching episodes in the past decade could be a preview of what is to come. Scientists have found strong correlations between unusually high water temperatures and bleaching in some areas. For instance, during the 1982-1983 El Nino event, during which unusually warm water flowed from South America's Pacific coast, up to 70%-90% of the corals off the Pacific coasts of Costa Rica, Panama, and Colombia died, and coral mortality was more than 95% off Ecuador's Galapagos Islands. Scientists have found that temperatures more than 4 |degrees~ Celsius above normal, even for a few hours, will result in greater than 90% coral mortality.

Although scientists cannot say that mass bleaching events prove that global warming is under way, the International Panel on Climate Change, a group of scientists assembled by the United Nations, has concluded that coral bleaching offers additional evidence that global temperatures are rising.

Already under way, stratospheric ozone depletion is expected to progress into the early part of the next century, increasing the intensity of the ultraviolet radiation that reaches the earth's surface in the equatorial region by 1%-10%. Increased ultraviolet radiation may already be damaging corals in the shallow portions of reefs. Corals in the shallows of a reef produce a natural sunscreen to protect themselves from the intense tropical sun. Ultraviolet radiation, however, can still harm these corals.

Setting Priorities

Coral reefs have surprised scientists with the rate at which they can recover once stress is relieved. When water quality is good, when plenty of larvae drift in from healthy reefs, and when the reef is sufficiently free of sediment and algae, scientists have found signs of recovery within a year, although it takes centuries to rebuild larger corals and missing sections of reef.

Thus, most coral reefs could begin to recover if governments pursued policies to protect and revive them. Currently, however, only a smattering of pilot projects and a few regional programs exist. To avoid continued reef decline in the decades ahead, countries need to pursue two areas of policy. One is the management and protection of reefs themselves, and the other is pollution prevention.

Australia pioneered reef protection in 1975 when it created the Great Barrier Reef Park. Under the founding legislation, the entire reef complex is part of a 350,000-square-kilometer park. But this is not a park in the traditional sense. The managers split the reef into sectors to satisfy various public demands: Some areas are restricted to scientific research, others allow tourists, and still others are open to commercial fishing and harvesting. The park authority monitors and regulates the use of the reef to try to ensure its long-term health.

In many countries, communities have demonstrated the value of locally managed fisheries. This approach draws on the lessons of traditional reef management. Given sufficient knowledge or training, local people are in the best position to manage the resource. If they also have exclusive rights to it, they have a strong incentive to manage a reef for long-term sustainability.

Conservation of the reef itself is vital, but not sufficient. Some sections of the Great Barrier Reef, for instance, are threatened by nutrients originating from the shore. Stopping coastal water pollution is thus a vital piece of the policy puzzle.

Although attractive to more and more people, coastal living has its own environmental costs. Mangroves and coastal wetlands--which are destroyed for homes, cities, and aquaculture--help protect coastlines from erosion, provide spawning grounds for oceanic fisheries, and are teeming ecosystems in their own right.

Where coastal development occurs, cities can regulate industrial and municipal discharge into coastal waters to attempt to prevent damage to reefs. Controlling this form of coastal pollution would benefit not only reefs and other marine ecosystems, but also public health.

The role of tourism is a controversial issue because tourists and tourist resorts can harm coral reefs, even though the money they attract should be strong motivation for countries to conserve the allure of their coasts. To begin to make tourism ecologically sound, local managers need to regulate it both in the water and on land and to apply some of their profits to conservation. If divers and tourists are told how to avoid damaging the reef, and if their numbers are limited, visitors are less likely to cause serious stress.

International Cooperation

Countries will also have to work with their neighbors to improve coastal water quality. A promising forum for cooperation is the Regional Seas Programme set up by UNEP in 1974. Under this initiative, countries establish goals and negotiate legally binding treaties to manage coastal waters. Ten regional programs now exist, encompassing most of the world's reefs, but so far the concept has fallen short of its potential due to lack of funds from member countries.

Since the international community has a stake in the biological health of reefs, it too has a role to play in their conservation. Growing recognition of the importance of reefs has prompted trade restrictions on corals, and seven reefs are now protected as World Heritage Sites. The World Bank plans to put 15%-20% of its $3-billion biodiversity budget into marine and coastal habitats, and the U.S. Agency for International Development and other national governments are cooperating with Southeast Asian nations on the conservation of their reefs.

One major contribution that industrial countries could make would be to map the world's reefs with satellite and airplane surveillance equipment. The U.S. National Aeronautics and Space Administration could do this as part of its Mission to Planet Earth program. Currently, countries do not have enough basic information on their total reef area to enable them to monitor the health of the reefs.

Prospects for Coral Reefs

The current rate of global environmental deterioration does not inspire hope that change will proceed rapidly enough to protect a significant portion of the world's reefs. A sense of imminent loss has led some scientists to propose that the few remaining undisturbed reefs should be protected before they too are damaged by expanding human activity.

But protecting only a few reefs for future generations and allowing the rest to continue on their current path of decline would be a crime against nature and would make the world a poorer place--aesthetically, biologically, economically, and culturally. Ultimately, it is as much a question of whether we save or destroy the world as it is a question of whether we save or destroy the world's coral reefs.

About the Author

Peter K. Weber is a research associate at the Worldwatch Institute, 1776 Massachusetts Avenue, N.W., Washington, D.C. 20036.

This article is adapted from his chapter in State of the World 1993 (W.W. Norton, 1993), which is available from the Futurist Bookstore for $10.95 ($9.95 for Society members), cat. no. B-1656.