美国科学60秒 SSS 2012-09-14（在线收听）

 Plants can pull carbon dioxide, the planet warming greenhouse gas, out of earth's atmosphere. But these aren't the only living organisms that affect carbon dioxide levels and thus global warming. Nope, I'm not talking about humans. Humble sea otters can also reduce greenhouse gases, but indirectly helping Kelp plants. That finding is in the Journal Frontiers in Ecology and the Environment. Researchers used 40 years of data to look at the effect of sea otter populations on Kelp. Depending on the plant density, one square meter of Kelp forest can absorb anywhere from tens to hundreds of grams of carbon per year. But when sea otters are around, kelp density is high and plants can suck more than twelve times as much carbon. That's because otters nosh on kelp-eating sea urchins. In the mammal's presence, the urchins hide away and feed on kelp detritus rather than living carbon absorbing plants. So climate researchers need to note that the herbivores plants and predators that eat them also have roles to play in the carbon cycle.