By Richard Black, BBC Environment Correspondent.

媒體英語會帶大家一起學習BBC撰稿人在報道世界大事時常用到的單詞和短語。

Background: 背景：新的調查研究顯示全世界蛇的總量在逐日減少。專家們在對歐洲、非洲和澳洲的8種蛇類進行考察后發現在過去15年中蛇的數量在這些地方驟減。

 

1998 seems to be the year when things started going wrong for the world's snakes.

Numbers of species such as European asps and west African vipers began falling then and in some places have plummeted since, by as much as ninety percent.

Some of the declines are clearly due to the spread of human settlements, but others have occurred in national parks and protected areas.

The scientists behind the study, which is published in the journal Biology Letters, say they have no idea what could be causing the trend.

Climate change is a possibility, as 1998 was an unusually hot year.

A similar decline noted a couple of decades ago in frogs was subsequently found to be due to the spread of a hitherto unknown disease, but there's no evidence yet for anything similar in snakes.

The scientists are calling for other researchers in other parts of the world to put forward any data they may have, in order to better understand the phenomenon and perhaps begin to detect what's causing it.