By Rajesh Mirchandani, BBC reporter, Los Angeles

媒体英语会带大家一起学习BBC撰稿人在报道世界大事时常用到的单词和短语。

Background: 美国政府指定阿拉斯加沿海的大片区域作为北极熊的危急栖息地。这片区域包括石油公司准备勘探的油区。环保人士希望这个举动能够挽救北极熊这个濒危物种的生存。

Right now in an icy den in the Arctic, a polar bear is giving birth to cubs, or is about to. But the very survival of this fearsome, majestic species concerns many humans.

Polar bears live and hunt on sea ice but the frozen Arctic Ocean is melting at an increasing rate, a result, scientists say, of global warming caused by greenhouse gases.

Now the US government has designated nearly half a million square kilometres in Alaska as critical habitats for the polar bear. It covers an area of roughlytwice the size of the United Kingdom, and it means any proposed economic activity there must be weighed against its impact on the bears’ habitat. It includes some of the Chukchi and Beaufort seas, exactly where the oil company Shell wants to drill.

The designation itself doesn't ban oil exploration, but it adds extra hurdles that opponents say will harm the economy.

Environmentalists welcome the move, saying now, they can write a recovery plan for polar bears, not an obituary.