These fish and snails have themselves experienced a decline in population because of overfishing by humans.

由于人类的过度捕捞，这些鱼和蜗牛的数量已经有所下降了。

youdao

Secondly, the marriage age in the West is rising, which contributes to the decline in population there.

其次，西方国家结婚年龄在上升，这也促使了人口的下降。

youdao

The dynamics vary significantly by region, with some regions, notably Europe, facing the prospects of a rapid decline in population and labor force.

各地区的发展趋势差异很大。有些地区，主要是欧洲地区，面临人口和劳动力急剧减少的前景。

youdao

Some believe that population is stable in contrast to the eastern portion of the stock which is continuing to decline at probably lower population levels."

VOA: standard.2010.03.04

That explains, in large part, why there was such a decline in population, why the Dark Ages were so dark, lots of poverty, lots of starvation, but also, as I suggested when I spoke of this earlier, also the freedom if you could make it, to learn and also to grow stronger.

这解释了,在绝大部分地区,为什么存在着这一类的人口消减,为什么黑暗时代如此黑暗,如此贫困,如此多的饥荒,但是同时,就如在我之前所提到的,同样可以,如果做得到的话,去学习以及使自身强大

耶鲁公开课 - 古希腊历史简介课程节选

Great crested newts became a European Protected Species following a dramatic decline in their population across Europe.

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In theory, the region should provide it with boundless opportunities to offset the decline in its population.

ECONOMIST: Friends and neighbours

The hedgehogs have been eating birds' eggs and chicks, leading to a big decline in the population of rare waders.

BBC: Hedgehogs get 'stay of execution'