The Biodiversity Crisis: Reefs in Crisis

Part of the Biodiversity Crisis Curriculum Collection.

By Barbie Bischoff

Massive Porites colony, Agincourt Reef, Outer Great Barrier Reef, Australia. Photo courtesy of Brian E. LaPointe.

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 seventy-five percent of the people live within six miles of the coastline. Natural events, such as El Niño, 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 more than fifty percent of the gross national product of several Caribbean countries; this provides 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 greatly 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. Because of poor agricultural practices and wetland destruction to make way for an increasing population, reefs are getting large doses of fertilizers from agricultural runoff. The nitrogen and phosphorus in the compounds have overnutrified the water, a condition called eutrophication, and allowed fibrous and fleshy lettuce-like algae to take hold along the reefs.

The creatures that are supposed to eat algae cannot keep pace with the accelerated growth and often abandon the reef in search of a more balanced environment. Eventually, the eutrophic reef becomes a ruin as the algae thrive, starving the coral of the sunlight it needs.

Underwater photo of two people in dark swim trunks at a coral reef.
Irresponsible tourism is a significant problem for reefs, especially in the Caribbean. Here, well-intentioned tourists stand on the live coral, which damages the tissues of the undersea colonies, often beyond repair and sometimes results in the destruction of entire reef tracts. Photo courtesy of S. J. Lutz.

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 harvesting methods, such as mechanical dredging or large-scale poisoning, irreparably damage the reefs. And overfishing has made the queen conch (a large, spiral-shelled mollusk), the spiny lobster, the whelk (a marine snail), the red snapper (a fish), and the Nassau grouper (a fish) commercially extinct in many localities. The once-abundant jewfish, a grouper, has virtually vanished from the Caribbean. In Haiti, populations of larger reef fish and lobsters are “crashing” (decreasing to very low levels) 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 such souvenirs as shells, coral skeletons, and 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. And in 1997, El Niño was unexpectedly intense. This caused ocean water temperatures to rise in many reef locations. This in turn produced the worst bleaching (expulsion of the colorful algae that live within corals) seen in the last decade. In 1998, similar El Niño–caused bleaching occurred in the Great Barrier Reef off Australia’s northeastern coast.

There is the potential for good news, however. Sanctuaries are beginning to change. Formerly designed as simply 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 hunting and fishing by local residents. 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 of good land management techniques is only beginning in many areas. Development within parks such as the Sian Ka’an Biosphere reserve, in the Yucatán Peninsula, is regulated. 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 residents to protect their nearby 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

Excerpted from Natural History, December 1997-January 1998.