By Paddy Clark, BBC News

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: 科学家们研究出一项新的方式来估计在地球上生物的总数，据统计一共有8百70万种不同类型的生物。这同过去使用的评估方式得到的结果差距很大。科学家们的发现将在网络科研期刊《生物科学公共图书馆》上发表。

It's generally accepted that very many species have yet to be discovered, but until now nobody has devised a reliable way to find out just how many. Suggestions for total numbers have ranged from 3 million to a hundred million, but most of these have been no more than intelligent guesses.

Scientists from the Census of Marine Life devised a counting method by identifying numerical patterns linking data on known species. They reckon that there should be about 8.7 million types of living organisms, three-quarters of them animals and the rest plants.

However, since the introduction of the current classification system by Carl Linnaeus in 1758, only a million and a quarter have been catalogued.

The scientists warn that human activity is hastening extinctions, and they note a touch wistfully, that many of the hitherto unknown species may vanish before we even know of their existence.