Global warming is having a big impact on some of the world’s animals. Scientists have found out that polar bears are becoming smaller because they do not get enough to eat.

A polar bear weighs only two-thirds of what it used to weigh 30 years ago. It is harder for them to hunt their main source of food—seals. In open water polar bears cannot catch them. They wait on the ice for them to come up for air， and then they snatch them. As the ice sheets in the Arctic are melting away， bears cannot get to their food so easily.

Other scientists say that instead of hunting seals， polar bears are now hunting each other in order to survive. An American government study predicted that global warming would kill two-thirds of the world’s polar bears by 2050. But if the melting of the ice sheets goes on at the current speed， the Arctic Ocean could be completely ice-free in the next 20 years.

全球變暖对世界上的一些动物产生了很大的影响。科学家们发现，北极熊正变得越来越小，因为它们无法摄入足够的食物。

现在的北极熊体重只有30年前的三分之二。它们更难猎取它们的主要食物来源——海豹。在无冰的水面，北极熊无法捕捉海豹。它们只能在冰面上等待海豹浮出水面呼吸，然后再伺机将它们掠走。由于北极地区的冰层正在融化，北极熊很难猎取食物。

其他科学家说，为了生存，北极熊现在不再猎杀海豹，而是相互猎杀。美国政府的一项研究预测，到2050年地球上三分之二的北极熊将死于全球变暖。但是，如果冰原继续以目前的速度融化下去，北冰洋可能在20年内完全无冰。

Word Bank

impact n. 影响；作用

weigh v. 有……重；称重

hunt v. 猎取；猎杀

snatch v. 抓走；抢去

instead of 代替；而不是

Now I can walk to work instead of going by car.

survive v. 生存；存活