A number of scientists question the assumption that the presence of alien species can never be acceptable in a natural ecosystem.

一些科学家质疑这样的假设，即在自然生态系统中，外来物种的出现是绝对不会被接受的。

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His tanks are part of a system very different from a fish farm or natural ecosystem.

Schreibman的鱼缸是某套系统的其中一部分组件。

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Wild animals are the important components of the natural ecosystem, theprecious wealth which universe altogether has.

野生动物是自然生态系统的重要组成部分，是全人类共有的宝贵财富。

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It is catastrophic to the natural ecosystem, and a problem for the fishing industry in the U.S., which looks at Asian Carp as an undesirable fish to eat.

VOA: standard.2010.07.20

Mr. LEACHMAN: If we lose the ferret from here, we lose an important part of our natural ecosystem.

NPR: Drilling to Begin in Colorado Ferret Habitat

Professor Johnson said he would also like to see large areas of Australia designated as "wild country", where dingoes were accepted as a natural part of the ecosystem.

BBC: NEWS | Science/Nature | Dingo has 'vital ecosystem role'

Permaculture also takes all the things we need -- our housing, energy sources, food and water supplies -- and tailors them to fit into the natural rhythms of the ecosystem.

CNN: Making barren lands bountiful