Wave of Marine Species Extinctions Feared
Wednesday, August 24, 2005
BIMINI, Bahamas -- The bulldozers moved slowly at first. Picking up speed, they pressed forward into a patch of dense mangrove trees that buckled and splintered like twigs. As the machines moved on, the pieces drifted out to sea.
Sitting in a small motorboat a few hundred yards offshore on a mid-July afternoon, Samuel H. Gruber -- a University of Miami professor who has devoted more than two decades to studying the lemon sharks that breed here -- plunged into despondency. The mangroves being ripped up to build a new resort provide food and protection that the sharks can't get in the open ocean, and Gruber fears the worst.
"At the end of my career, I get to document the destruction of the species I've been documenting for 20 years," he lamented as he watched the bulldozers. "Wonderful."
Gruber's sentiments have become increasingly common in recent years among a growing number of marine biologists, who find themselves studying species in danger of disappearing. For years, many scientists and regulators believed the oceans were so vast there was little risk of marine species dying out. Now, some suspect the world is on the cusp of what Ellen K. Pikitch, executive director of the Pew Institute for Ocean Science, calls "a gathering wave of ocean extinctions." Dozens of biologists believe the seas have reached a tipping point, with scores of species of ocean-dwelling fish, birds and mammals edging toward extinction. In the past 300 years, researchers have documented the global extinction of just 21 marine species -- and 16 have occurred since 1972.
Since the 1700s, another 112 species have died out in particular regions, and that trend, too, has accelerated since the mid-1960s: Nearly two dozen shark species are close to disappearing, according to the World Conservation Union, an international coalition of government and advocacy groups.
"It's been a slow-motion disaster," said Boris Worm, a professor at Canada's Dalhousie University, whose 2003 study that found that 90 percent of the top predator fish have vanished from the oceans. "It's silent and invisible. People don't imagine this. It hasn't captured our imagination, like the rain forest."
Many activists have focused on the plight of creatures such as the ivory-billed woodpecker and the grizzly bear, but relatively few have taken up the cause of marine species. Ocean dwellers are harder to track, and some produce so many offspring they can seem invulnerable. And, in the words of Ocean Conservancy shark fisheries expert Sonja Fordham, often "they're not very fuzzy."
Although a number of previous extinctions involved birds and marine mammals, it is the fate of many fish that worries experts. The large-scale industrialization of the fishing industry after World War II, a global boom in oceanfront development and a rise in global temperatures are all causing fish populations to plummet.
"Extinctions happen in the ocean; the fossil record shows that marine species have disappeared since life began in the sea," said Elliott A. Norse, who heads the Marine Conservation Biology Institute in Redmond, Wash. "The question is, are humans a major new force causing marine extinctions? The evidence, and projections scientists are making, suggest that the answer is yes."
Large-scale fishing accounts for more than half of the documented fish extinctions in recent years, Nicholas K. Dulvy, a scientist at Lowestoft Laboratory in England, wrote in 2003. Destruction of habitats in which fish spawn or feed is responsible for another third. Warmer ocean temperatures are another threat, as some fish struggle to adapt to hotter and saltier water that can attract new competitors.
But nothing has pushed marine life to the edge of extinction more than aggressive fishing. Aided by technology -- industrial trawlers and factory ships deploy radar and sonar to scour the seas with precision and drag nets the size of jumbo jets along the sea floor -- ocean fish catches tripled between 1950 and 1992.
In some cases, fishermen have intentionally exploited species until they died out, such as the New Zealand grayling fish and the Caribbean monk seal; other species have been accidental victims of long lines or nets intended for other catches. Over the past two decades, accidental bycatch alone accounted for an 89 percent decline in hammerhead sharks in the Northeast Atlantic.