The world's biggest risks
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The Earth's dying oceans threatened with mass extinction

A wholesaler checks the quality of frozen tuna displayed at the Tsukiji fish market before the New Year's auction in Tokyo January 5, 2015.

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Overfishing

Around 90 percent of the world's fisheries are either "fully exploited, overexploited or have collapsed," according to the Monterey Bay Aquarium. More than twice as many fishing boats than fishery stocks can sustain are in the water. "There are simply too many boats chasing a dwindling number of fish," said an aquarium spokesperson.

Organizations such as the Monterey Bay Aquarium publish updated "Seafood Watch" guides that advise consumers on which kinds of fish are being overfished, but these approaches require that customers care enough about the issue to make use of them.

Other approaches toward the regulation of fishing are being implemented, such as cutting fishing seasons short, setting limits on the number of fish a boat can take in a season, or suspending fishing in overharvested areas until populations rebound.

Thomas Peter | Reuters