Corals under siege
Christl Denecke, Programme fellow at the Coral Reef Alliance (Berkeley, California).
No more shelter for fish: a diver explores a blasted reef.
Threatened by pollution, overfishing and global warming, coral reefs a lifeline for millions of peopleare dying off at an alarming rate
The vibrantly coloured rainforests of the sea received a disturbing bill of health during a recent gathering of marine biologists in Bali: in the past few decades, more than one quarter of the worlds coral reefs have been destroyed by human activity. At the present rate, at least 57 percent will be lost within our lifetime.
This destruction threatens not only coral reefs, but also the lives of some 500 million or so people in southeast and southern Asia, eastern Africa and the Caribbean. For many of these coastal communities, corals are the largest source of protein: a healthy reef can provide more than 15 tonnes of fish and seafood per square kilometre each year, enough food for 2,500 people. And often they are the only source of income, employment and foreign exchange.
Coastal communities depend on their reefs to attract tourists, develop the capacity for commercial fishing, and protect shorelines from erosion and storm damage. In the British Virgin Islands, for example, 45 percent of revenue comes from tourism, which provides more than half of the territorys employment. A loss of reefs would probably cause the water to cloud with algae and the beaches to erode under the pressure of waves, leading to an estimated $130 million loss in income.
Created by more than 50 million years of evolution, coral reefs are one of the most complex and fragile webs of biodiversity on earth. Naturalists have catalogued more than 800 species of reef-building coral and 4,000 species of reef-dwelling fish. In total, coral reefs may shelter as many as one quarter of all marine species, and are especially important as nurseries for young fish.
So why are these lifelines disappearing faster than ever? On a local level, overfishing has decimated many individual reefs, notably in Malaysia, Vietnam, Indonesia and the Philippines. The removal of too many plant-eating fish allows algae to overgrow and kill the coral, beginning a chain reaction of local extinctions that quickly grows beyond the reefs natural ability to recover. Several fishing techniques are particularly lethal.
Blast fishing, when fishers explode homemade devices over reefs to kill fish, has severely damaged corals in eastern Africa. Fishing with sodium cyanide is no better: exposure to this chemical makes tropical fish slow and clumsy, and therefore much easier to catch, while at the same time killing off corals and many other reef animals.
Cyanide-fished reefs are often stripped of their marine life and overgrown by algae. Despite efforts to halt cyanide fishing, its frequency has increased in the past few years, driven by the high prices paid for live fish at tropical fish restaurants in Asia and aquariums in North America. Since this form of fishing began in the 1960s, the amount of cyanide dumped on coral reefs in the Philippines alone has exceeded one million kilograms.
But fishing is just one chapter of the story. Reefs are also being killed by industrial pollution, sediments running down rivers from deforested land and run-off from agricultural fertilizers. Activities such as coral mining, dredging, ship-grounding and construction break apart large coral strips and shatter delicate branches. Since reef-building corals only grow at a rate of 1.3 to 10.2 centimetres per year, each blast-fishing explosion and dragged object can destroy a century of reef development.
To make matters worse, global warming is adding to the plight of the reefs. Not only are corals fragile, but they are highly sensitive to temperature change. So when the 1998 El Niño winds warmed tropical waters from Africa through Indonesia and the Philippines and out into the Pacific, reefs in the region turned pale and quickly faded to an eerie shade of bone white, a phenomenon known as bleaching. Many bleached corals are finally killed by algae. The Global Coral Reef Monitoring Network estimates that bleaching in 1998 destroyed 16 percent of the earths reefs. In the Indian Ocean, the Maldives, Sri Lanka and western India, bleaching had a devastating effect on reefs already damaged by sedimentation and pollution from onshore industry and land-clearing. Those that continue to be exposed to harmful human impacts are unlikely to ever recover. Above and beyond all other destructive pressures, theres a good chance that coral reefs as we know them will be gone in 30 to 50 years if global warming continues as expected.
While communities cannot do much about global warming, they can find ways to ally protection with economic growth. For example, tourism development and coral protection go hand-in-hand at the Bonaire Marine Park in the Dutch Antilles. The park, established in 1979, employs rangers to enforce bans on the collection of coral, spearfishing and commercial fishing in park areas. To make the park self-sustaining, managers began charging a user fee to all visitors in 1992. Bonaire was one of the first marine parks to fund itself, instead of relying on money from foundations or local taxes.
Now, the degradation of unprotected reefs elsewhere in the Caribbean has left Bonaire with some of the healthiest coral in the area. Almost 30,000 visitors flock to the park each year, which has fed Bonaires tourism industry. The continuing efforts of park rangers to protect their reefs indicate that the island is set to maintain healthy coral and increase its revenue from tourism.
Bonaire is just one example of about 400 marine parks designed to protect reefs. Unfortunately, many of these are paper parks, lacking the funding or community support to enforce protection laws. Many are geographically isolated and, more often than not, near coastlines that are not managed properly, allowing erosion and chemicals from areas outside the park to flow in and damage coral.
With financial resources in developing countries stretched thin, the most effective path to protection lies in partnerships between local governments, international aid groups, NGOs and national foundations. The goal: to design effectively managed marine parks where communities maintain control over their resources with help from more experienced and better funded national or international organizations. Wealthy nations have an added stake in these biodiversity havens: they could well harbour precious chemicals for developing medicine. The most notable is azidothymidine (AZT), a drug widely used in industrialized countries to treat people with AIDS. AZT was created from a chemical produced by a
Caribbean sea sponge that slows the growth of viruses. It is unknown how many more chemicals derived from coral reef animals may become the basis for similar life-saving drugs, but that is just one more good reason for speeding up the protection of our imperilled reefs.