To test this, they had first to establish a reliable list of invaders. That is not as easy as it sounds. As they observe, “although there are many lists of invasive species published by governmental agencies, inclusion of a given species in the lists may not be entirely free of political motivation”. Instead, they polled established researchers in the field of alien species, asking each to list ten invasive species and, for comparison, ten aliens that just rubbed along quietly with their neighbours. The result was a list of 21 species widely agreed to be invasive and, for comparison, 18 non-invasive aliens.
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They are hiding behind some rocks as they observe a pride of lions.
他们正躲在一些岩石的后面观察一群狮子。
The whole team would have access to the risk repository and would be able to enter risks as they observe them.
整个团队的所有成员都可以访问风险数据库，并且可以输入他们观察到的风险。
The birds are hard to observe, as they live in a region of mountainous forest, so the researchers have attached tiny cameras to the tails of some birds, as one method of investigating their behaviour.
这些鸟很难观察，因为它们生活在山区森林里，所以研究人员在一些鸟的尾巴上安装了微型摄像机，以此作为一种研究它们行为的方法。
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