Are we causing a mass extinction in our oceans?

"The big picture is, if you're looking in places for which we have good data" – Europe, North America, New Zealand, Australia and the high seas – "fish populations are generally stable and in some cases improving, especially in the U.S.," said Ray Hilborn, a population ecologist at the University of Washington. Hilborn is co-author of a 2009 article published in the journal Science that found reason for hope in certain ecosystems, where management practices have prevented or, more frequently, reduced overfishing.

But given the lack of international oversight on fisheries, "I'm not terribly optimistic about their future," Hilborn said.

Boris Worm, a marine biologist at Dalhousie University in Nova Scotia, Canada, and the lead author of the 2009 fisheries study, was less optimistic about the current health of fisheries. "Even in the best places it's very mixed," he said.

Humanity has solutions

Tony Haymet, director of the Scripps Institution of Oceanography at the University of California, San Diego, describes the oceans, like the atmosphere, as victims of "the tragedy of the commons: everybody owns them, and nobody owns them."

"But on the positive side, there are three things that I think that at least we have the prospect of addressing," he said. These include signs of international movement to address overfishing, the creation of marine reserves, and the prospect that the U.S. Senate might finally ratify the United Nations Convention on the Law of the Sea, which establishes international rules governing the use of the oceans.

Although there are hurdles, aquaculture also has the potential to become a safe, sustainable source of protein, he said.

Others aren't so optimistic. Humans have the technology and the knowledge to stop the ecological havoc we are wreaking, but we lack the wisdom to use it responsibly, Caldeira told LiveScience in an e-mail.

"If current trends continue, the extinctions of the coming decades will be clearly visible to future geologists comparable in scale to the great extinction events in Earth's history," he wrote. "I think it will be an enigmatic extinction. Future geologists will try to figure out why we apparently tried to kill off so many species, but they will find it hard to believe that simple reason is stupidity."

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