Damage to Coral Reefs Mounts, Study Says

Following the grim path of the rain forests and the Arctic, coral reefs are becoming the latest victim of the modern human plagues of pollution, over-harvesting and climate change, according to a massive survey of these sensitive ocean gardens.

Key species of fish, shrimp and lobster are missing from the majority of the reefs that were studied as fishermen pour cyanide and blast dynamite within the antler-like branches of many coral heads to collect seafood.

At the same time, polluted runoff from coastal communities is providing a continual stream of fertilizer onto many reefs, feeding species of large and fleshy algae that choke off growth of the type of hard, stony corals that make up the foundation of the reefs, according to the study by Reef Check, a monitoring program based at UCLA’s Institute of the Environment.

The study, involving more than 5,000 scientists and divers who over the course of five years tracked the transformation of coral reefs in 55 countries, found only one reef out of more than 1,100 that was judged to be in near-pristine condition.

“Coral reefs have suffered more damage over the last 20 years than they have in the last 1,000,” said Gregor Hodgson, a visiting UCLA professor who heads Reef Check and is the author of the report. “It is the rate of decline and the global extent of the damage that is so alarming, with species reasonably abundant 30 years ago now on the verge of extinction.”

The growing destruction of these fragile yet bony ecosystems, often called the rain forests of the oceans, has alarmed scientists because coral reefs account for 25% of all marine fish species and provide food for 350 million people, mostly in developing nations, Hodgson said.

Although reefs make up just one-tenth of 1% of the world’s ocean area, authors of the study called them a key indicator of the health of the world’s oceans.

Moreover, the rocky, physical structure of reefs provides crucial protection for many coastal regions from the severity of storms, and their continual growth and erosion replenish the white-sand beaches so prized in the multibillion-dollar tourist industry, often the major source of income in poor tropical nations.

Coral reefs are fertile breeding grounds for marine life. If it were not for insects in rain forests, reefs would have the highest species diversity of any habitat in the world.

Coral reefs are more than 100 million years old and are among the largest living structures on Earth. The Great Barrier Reef off Australia is more than 1,200 miles long and is visible from outer space.

One of the biggest threats to the reefs are ocean temperature spikes that many marine biologists attribute to global warming and short-term climate phenomena such as El Nino. Corals are unusual animals because they thrive close to the upper range of their temperature tolerance. Upward changes of just a few degrees over a sustained period cause the symbiotic microorganisms living within the coral tissue, which provide energy for the colony, to either leave or be expelled by the coral.

Known as coral bleaching, this phenomenon has killed massive stands of coral in recent years in the tropical Pacific Ocean, including giant colonies that scientists believe were as much as 1,000 years old. It has made the surviving coral susceptible to a variety of diseases. One large episode in 1997 and 1998 reduced the world’s live coral growth by 10%, according to the study.

Overfishing is threatening to put four species of fish in danger of extinction and is depleting many other reef fish and shellfish at alarming rates, Hodgson said.

Predators such as the Nassau grouper, Barramundi cod and hump-head wrasse were missing from at least eight of every 10 reefs surveyed.

These big fish are prized in Hong Kong and other East Asian markets where restaurants allow customers to select a live fish from an aquarium and have it cooked for them. This live-fish trade, where fishermen in Indonesia and the Philippines often squirt cyanide into the reefs to stun the fish, also can kill nearby animals and the coral.

Other destructive fishing techniques include throwing explosives into the reefs to stun or kill the fish to make them easier to harvest.

Bump-head parrot fish, important because they crush coral with their jaws, helping to create sand, were absent in 89% of the reefs.

The triton--often collected for the souvenir market because of its distinctive shell shape--and the spiny lobster also appeared scarce. Triton harvesting is especially damaging because it is the primary predator of the coral-gobbling crown of thorns sea star. The survey sighted only 101 of the large shelled mollusks--harvested by the thousands as recently as the 1960s, Hodgson said.

Reef Check divers saw fewer numbers of some species of smaller fish, shrimp and invertebrates that are caught live to be sold for display in home aquariums.

Gary Ostrander, a biologist and coral reef expert at Johns Hopkins University in Baltimore, cautioned that Reef Check’s numbers at best only point to areas where more research is required.

“You have to be careful with this kind of information,” Ostrander said. “Tritons, for example, are very low-density animals on the reef and it is not surprising that they did not see a lot. While the Nassau grouper is clearly in trouble, the ones that I see are a lot smaller than what we would like, but I can tell you of about 50 reefs where I work where we see the groupers.”

Hodgson said the Reef Check project is designed to be an early warning system and that he hopes other scientists look at the issues raised in his report and make them targets of their research.

“Although it is a big study, we have looked at only a tiny fraction of the world’s reefs,” he said.

Hodgson conceded that scientists really don’t have a good idea of how a pristine reef should look or of the natural cycles of reef life.

“If you go back through the records of ship captains and naturalists for hundreds of years, you find that humans have a very long record of exporting reef organisms, sometimes in astounding numbers,” he said. “We might not have had a pristine reef for centuries and we really don’t know what the baseline should look like.”

Ostrander said the general message that reefs are under assault is correct.

“We have definitely seen changes in the reefs within the last five years,” he said. “Species diversity is going down.”

Ostrander said he believes environmental factors have made coral especially susceptible to bleaching and disease.

“A lot of us are trying to figure out what part of this is natural and what part is the effect of humans on the ecosystem,” Ostrander said.

The biologist said he is concerned about the discovery of problems on remote reefs, far from human habitation.

“You have to ask yourself what is happening here and where it will happen next,” Ostrander said. “Could it happen on land in the forests and prairies? We just don’t know.”

Not all of Reef Check’s findings were grim.

“Modern coral reefs have been around for 100 million years, and they can be surprisingly resilient,” Hodgson said.

“Ecologists have been surprised at how quickly reef fish populations have rebounded at successful marine parks,” he added. “Two years is enough to replenish many species. Some types of corals also grow very quickly--like corn--but others take decades to reach a large size.”

Reef Check scientists said the establishment of more marine parks and restricted fishing zones internationally will help over-fished species rebound by creating breeding refuges.

Hodgson, Ostrander and other marine biologists said more money needs to be invested in technology to farm reef organisms for the food and aquarium industries.

“The demand for reef fish and shellfish far exceeds the supply,” Hodgson said. “Unless we can invest in the research and development to aquaculture some of the high-value organisms in environmentally acceptable ways, they will become extinct.”