時差N小時:過度捕鯨與環(huán)境

Until recently, when scientists studied changes inopen-ocean ecosystems, they looked at changes inthe bottom of the food chain that gradually maketheir way to the top, like foodshortages and shifts inthe ocean environment.

直到最近，當科學家們在研究遠洋地區(qū)生態(tài)系統(tǒng)的變化時，他們觀察了處于食物鏈最底層并且在慢慢上升的變化，比如說食物短缺、海洋環(huán)境的變化。

A recent study,however, suggests that moreattention needs to be given totop-down influences aswell.

然而，最近的一項調(diào)查顯示，人們還應該更多的注意自上而下的影響。

For example, over the past few decades, there's been a major collapse of the populationsofharbor seals, fur seals, sea lions, and sea otters living on the coasts of western Alaska.

比方說，在過去的幾十年里，生活在阿拉斯加西海岸的斑海豹、海狗、海獅和海獺數(shù)量極具下降。

Now a newstudy suggests that all this destruction can be traced back to humans overfishingsperm andbaleen whales between 1946 and 1979.

現(xiàn)在，一項新的調(diào)查顯示，所有的這些毀壞都可以歸咎于人類在1946年到1979年期間過度捕撈抹香鯨和須鯨。

Killer whales, who live at the top of the ocean food chain, used to prey on sperm andbaleenwhales.

虎鯨是在海洋食物鏈的最高層，它習慣于捕食抹香鯨和須鯨。

When these were no longer available, the killer whales were forced to fish farther down thefood chain.

當虎鯨不能再捕食它們的時候，它就被迫捕食處于更下一層的食物鏈。

First they fed on seals, which were the easiest to catch and the most nutritionallyvaluable.

她們先捕食的是最容易捕捉且最有營養(yǎng)價值的海豹。

Then, when seals became rare, the killer whales turned to sea lions.

接著，當海豹變得稀少后，虎鯨便轉(zhuǎn)向了海獅。

When the sea lionpopulation crashed, they started fishing sea otters.

而又當海獅的數(shù)量變少后，虎鯨又開始獵殺海獺了。

The domino effect reaches even farther.

多米諾效應又繼續(xù)延伸。

Without sea otters keeping sea urchins in check, their population has exploded.

沒了海獺約束海膽，海膽的數(shù)量變得龐大起來。

And they'vedestroyed the kelp forests, and with it, the kelp forest ecosystem in southwesternAlaska.

并且破壞阿拉斯加啊西南部的海藻林生態(tài)系統(tǒng)。

Animals switching food sources can have a very serious effect on the environment.

動物間交換食物來源對環(huán)境有著很嚴重的影響。

And thatwe humans, as the ultimate predators, need to give a lot of thought to the choices wemake.

而作為終極捕食者，人類需要好好思考一下他們所做的選擇。

They may affect the food web in unintended ways.

這些選擇可能會以人們所不知道的方式來影響食物網(wǎng)。