Are sharks in danger of extinction

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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 do their work. “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 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 towards extinction. In the past 300 years, researchers have documented the global extinction of just 21 marine species – and 16 of those extinctions 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 on the brink of 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 who wrote a 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.”

“Extinctions happen in the ocean; the fossil record shows that marine species have disappeared since life began in the sea,” said Elliott 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.”