昆虫和病原体是森林生态系统的固有成分，通常其密度相对较低，所造成的损害较小，对树木生长及其活力的影响微乎其微。
Insects and pathogens are integral components of forest ecosystems and normally are present at a relatively low density, causing little damage, and having negligible impact on tree growth and vigour.
一项人体细菌生态系统调查报告显示，细菌的高密度聚集区时人体的前臂，而且这仅是意外的开始。
According to a new survey of the bacterial ecosystem that covers us, the diversity hot spot of the body's exterior is the forearm. And the surprises don't end there.
城市作为高密度的人类聚居地，人类活动与生态环境的矛盾尤为突出。
City as high human settlement of density, the conflict between the human activity and the ecological environment was particularly outstanding.
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