This is Scientific American — 60-Second Science. I'm Emily Schwing.
When you look at satellite images it's easy to pick out hurricanes, deserts, and the work of a certain semiaquatic rodent:
"And the reason you can see beaver activity from space is because they leave a mark on the landscape."
Ken Tape is an Arctic Ecologist at the University of Alaska Fairbanks.
"So they make these ponds, and when a pond forms my idea was that we could infer, if it was a certain kind of pond and we could see a beaver dam, then we could infer that beavers had moved into that area, or moved out of that area if it's a beaver pond that's drained."
Tape and a team of other scientists used Landsat satellite images that cover more than 19,000 square kilometers of Arctic tundra in Alaska.
"We saw lots of new beaver ponds, I think we saw 56 new beaver ponds formed between 1999 and 2014."
Beavers are considered keystone species, which have an outsized effect on their ecosystem.
"And I think it's particularly true in the Arctic because it's underlain by all this frozen ground."
He's talking about permafrost.
"And what happens is when you start flooding permafrost areas, permafrost starts to deteriorate. And really the glue that's binding the soil together, that's holding the landscape together starts to thaw."
Tape and colleagues presented their findings December 11th at the annual conference of the American Geophysical Union. He says the implications of beavers' northward expansion are big.
"Imagine that you just dropped 56 groundwater springs into Arctic stream environments. A groundwater spring in the Arctic is a rare thing in the Arctic and it's an oasis of biologic activity for fish spawning and things like that."
Beavers may be following the northward expansion of vegetation onto the tundra.
"But the other possible driver is rebound from heavy trapping a century ago."
If they contribute to the deterioration of the permafrost, you could call it coming back with a vengeance.
Thanks for listening the Scientific American — 60-Second Science. I'm Emily Schwing.
“永久冻土区被水淹没后会开始解冻 。也就是说，粘合土壤、连接地形的胶开始溶解 。”
在12月11日举行的美国地球物理学会会议上，泰普和同事展示了他们的研究结果 。泰普表示，海狸向北扩张有重大影响 。
“想象一下，在北极河流环境中放入56个潜水泉 。潜水泉在北极很罕见，它是鱼类产卵等生物活动的乐土 。”
谢谢大家收听科学美国人——60秒科学 。我是埃米莉·施温 。
1. pick out 辨认出；分辨出；
例句：The detective-constable picked out the words with difficulty.
2. lots of 许多；很多；大量；
例句：We took lots of measurements.
3. contribute to 促成；促使；是导致…的原因之一；
例句：There is no doubt that these measures will contribute to the solution of the problem.
4. come back 回来，回去；
例句：She's going to come back every so often.