Predators are an essential factor in maintaining communities that are rich and diverse in species.

捕食者是维持群落物种丰富多样的一个重要因素。

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They prevent fish migrations and change aquatic habitats essential for native species.

它们阻止了鱼类迁徙，并改变了对本地物种至关重要的水生栖息地。

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Such assistance was essential in identifying potential dangers—poisonous species, unpredictable rivers, uncharted territories—which could mean the difference between life and death.

这种援助对于查明潜在危险——有毒物种、不可预测的河流、未知领域——至关重要，那些危险可能意味着生死之差。

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However, the organisations have said they would withdraw their objections if SSE was willing to work with them on reducing any risks to water courses essential to species such as Atlantic salmon and sea trout.

BBC: SSE asked to protect salmon from Sutherland wind farm

No issue is more essential to our survival as a species.

UN: Secretary-General

More than 20 species have been successfully cloned, and there is now talk in some conservation circles of a veritable Jurassic Park-effect becoming essential, as the rate of species extinctions exceeds anything biologists even a generation ago could have imagined.

FORBES: July 5th: Interdependence Day