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.

全球變暖對世界上的一些動物產(chǎn)生了很大的影響。科學(xué)家們發(fā)現(xiàn)，北極熊正變得越來越小，因?yàn)樗鼈儫o法攝入足夠的食物。

現(xiàn)在的北極熊體重只有30年前的三分之二。它們更難獵取它們的主要食物來源——海豹。在無冰的水面，北極熊無法捕捉海豹。它們只能在冰面上等待海豹浮出水面呼吸，然后再伺機(jī)將它們掠走。由于北極地區(qū)的冰層正在融化，北極熊很難獵取食物。

其他科學(xué)家說，為了生存，北極熊現(xiàn)在不再獵殺海豹，而是相互獵殺。美國政府的一項(xiàng)研究預(yù)測，到2050年地球上三分之二的北極熊將死于全球變暖。但是，如果冰原繼續(xù)以目前的速度融化下去，北冰洋可能在20年內(nèi)完全無冰。

Word Bank

impact n. 影響；作用

weigh v. 有……重；稱重

hunt v. 獵取；獵殺

snatch v. 抓走；搶去

instead of 代替；而不是

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

survive v. 生存；存活