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1 .This is Scientific American 60-Second Science. I'm Christopher Intagliata. Got a minute?
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2 .What human activity has the biggest impact on the planet?
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3 .I took an informal poll of New Yorkers:
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4 ."Driving, day to day commuting."
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5 ."Eating too much meat."
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6 ."Using too many resources, I think."
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7 ."Factory farming."
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8 ."Driving."
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9 .Here're something I didn't hear: killing off the world's top carnivores, like tigers, wolves and bears.
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10 .Scientists say it's an overlooked problem with effects that ripple through ecosystems in unexpected ways.
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11 .When otters disappear, for example, urchins take over, decimating kelp forests.
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12 .Researchers reviewed the conservation status of 31 of the world's largest carnivorous mammals.
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13 .They found that some two-thirds are threatened, living on a fraction of their former range.
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14 .And nearly all are decreasing in number, apart from a few exceptions, like grizzlies and black bears.
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15 .Their analysis appears in the journal Science.
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16 .The loss of top carnivores could alter the dynamics of disease and wildfires, they say, and have unintended consequences for ecosystems.
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17 .So either we learn to coexist with these predators or their disappearance may come back to bite us.
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18 .Thanks for the minute, for Scientific American 60-Second Science. I'm Christopher Intagliata.
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