Reefs in crisis

Natural History, Dec-Jan, 1997 by Barbie Bischof

Humans have harmlessly harvested the rich wildlife on coral reefs for thousands, perhaps hundreds of thousands, of years. But in the late twentieth century, human pressures -- including a population explosion and migration to coastal areas -- have placed reefs at risk. In the Caribbean basin, the population has quadrupled since 1960, and 75 percent of the people live within six miles of the coastline. Natural events, such as El Nino, have also played a role in the decline of reefs. And tourism has been both blessing and bane.

According to a report issued by the International Coral Reef Initiative, tourism accounts for over 50 percent of the gross national product of several Caribbean countries, providing an economic incentive for reef protection. But more visitors means more coral collecting and more damage caused by swimmers, divers, and boat anchors. Moreover, the clearing of land to make way for hotels and homes has exponentially, increased the rate of shoreline erosion. Without the natural filter provided by wetland vegetation, soil pours into the sea, blocking the sunlight vital to corals and choking the pores of sponges and other reef creatures. On some reefs, nitrogen and phosphorus -- runoff from farm fertilizers -- have overfed algae, creating a blanket of vegetation that suffocates the coral and inhibits the settlement of larval corals oil the reef.

Coastal waters are degraded off southern Florida, Haiti, Cuba, the Dominican Republic, and Veracruz, Mexico. Haiti's case is acute, because only one percent of native coastal vegetation remains, and sewage treatment plants have yet to be built. Contamination from fossil fuels, industrial chemicals, and pesticides -- as well as domestic and animal waste -- is also a problem throughout the Caribbean.

Like other developing nations, some Caribbean countries are forced to survive by overexploiting their own resources for the global market. And coral reefs, which occupy, only about 0.2 percent of the world's oceans, supply about 9 million of the 80 million tons of fish harvested worldwide each year. Some of the harvesting methods, such as mechanical dredging or large-scale poisoning, irreparably damage the reefs. And overfishing has made the queen conch, spiny lobster, whelk, red snapper, and Nassau grouper commercially extinct in many localities. The once-abundant jewfish, a grouper has virtually vanished from the Caribbean. In Haiti, larger reef fish and lobster populations are crashing because many of these animals are taken from the sea before reaching reproductive maturity.

Commercially desirable fish and crustaceans aren't the only casualties. Illegal sale of turtles is common in the Dominican Republic, the Bahamas, and Mexico. Tourists' fancy for souvenirs such as shells, coral skeletons, other curios has depleted black coral and mollusks. Meanwhile, a growing aquarium trade has overharvested smaller, ornamental fishes.

The incidence of coral disease is also climbing (see "Emerging Infections on the Reefs," page 48). And in 1997, El Nino was unexpectedly intense, producing the worst bleaching (expulsion of the colorful algae that live within corals) seen in the last decade.

There is the potential for good news, however. Sanctuaries are beginning to change. Formerly designed as just small, totally protected areas, they had little impact on the health of reefs. Now the trend is to divide large areas into zones for distinct uses, such as fishing, tourism, shipping, defense, collecting, scientific research, and indigenous hunting and fishing. Florida Keys National Marine Sanctuary is among those successfully adopting this approach. Many parks throughout the Caribbean, however, don't have the funding necessary for maintenance and enforcement.

While scientists have long recognized the importance of the land-water connection to reef health, implementation good land management techniques is only beginning in many areas. Development within parks such as the Sian Ka'an Biosphere reserve, in the Yucatan Peninsula, is at least theoretically controlled. In the United States, Florida now requires barriers to control sediment generated by construction projects.

In 1997 -- the International Year of the Reef -- a public awareness campaign, conducted on a grass-roots level, attempted to inspire local stewardship of reef ecosystems. Within the last few years, various organizations have begun to sponsor monitoring programs, mapping expeditions, scientific research, and focused conservation and management efforts.

Barbie Bischof is a Miami-based science writer. In preparing this section, she consulted with Robert Ginsburg, professor of marine geology and geophysics at the Rosenstiel School of Marine and Atmospheric Science, University of Miami.