Trawlers Destroying Deep-Sea Reefs, Scientists Say

Trawlers Destroying Deep-Sea Reefs, Scientists Say

John Pickrellfor
National Geographic News
February 19, 2004

Typically imagined as explosions of color in shallow, warm, azure tropical waters, coral reefs are often regarded as the rain forests of the sea. It wasn't until recent years that scientists realized that reefs at much greater and darker depths also teem with life—and may be home to the majority of coral species.

Yet even before these deep reefs have been fully explored and documented, they are being destroyed by unregulated deep-sea trawling. Concerned that many species may be lost before they are identified, a group of 1,136 scientists from 69 countries is appealing for new laws to protect deep-ocean corals and sponges.

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"Based on current knowledge, deep-sea coral and sponge communities appear to be as important to the biodiversity of the oceans and the sustainability of fisheries as their analogues in shallow tropical waters," said a statement released earlier this week at both the American Association for the Advancement of Science meeting in Seattle and the United Nations Convention on Biological Diversity held in Kuala Lumpur, Malaysia.

"We urge the United Nations and appropriate international bodies to establish a moratorium on bottom trawling on the high seas," the scientists said. They include Harvard University's renowned ecologist Edward O. Wilson and former head of the U.S. National Oceanic and Atmospheric Administration, D. James Baker.

Great Depths
Scientists first discovered deep-sea coral forests in the 19th century but only recently realized how widespread and important they are. Growing to hundreds, or even thousands of years old, deep-sea corals are filter-feeding organisms that can form dense reefs in cold and deep waters as far apart as Alaska, Tasmania, Ireland, and Colombia.

Dated at 1,800 years old, one slow-growing deep-sea coral may rival some kinds of pine trees as the world's oldest organism. Some of these corals even resemble trees, growing up to 10 meters (33 feet) in height. They have been discovered as deep as 3.5 kilometers (2.2 miles). Lophelia coral reefs in cold North Atlantic waters can harbor 1,300 invertebrate species, and 850 species of coral have been found on underwater plateaus of the Tasman and Coral Seas.

These forests provide habitats for huge numbers of important deep-sea species, the scientists said Individual corals could produce chemicals potentially useful for treating high blood pressure, cancer, and chronic pain.

However, many species are being discovered only as they are destroyed by fishing, said Lance E. Morgan. Morgan is chief scientist with the U.S.-based Marine Conservation Biology Institute (MCBI), the nongovernmental organization responsible for organizing the petition. "Norway only found that it had these corals because of surveys for oil," Morgan said. "So they were discovered and significantly damaged at the same time."

Though oil and gas prospecting, deep-sea mining, and global warming are all significant threats, today's greatest danger comes from fishing trawlers, the scientists wrote.

Indiscriminate Destruction
Trawlers are fishing vessels that drag enormous and heavily weighted fishing nets at great depths across the seafloor. These can be weighted with rollers or chains that crush everything in their path, Morgan said, smashing corals and sponges and killing enormous quantities of nontargeted animals as well as the fish (including Chilean sea bass, orange roughy, and cod) and shrimp the nets are set to catch.