Of the 7,000 alien species in the United States—out of a total of 150,000 species—only about 10% are invasive.

在美国总共15万的物种中，有7000种外来物种，当中只有10%是入侵物种。

Ecologists generally define an alien species as one that people, accidentally or deliberately, carried to its new location.

生态学家通常把外来物种定义为人们偶然或故意带到新地方的物种。

What can be done about invasive alien species?

怎样处理外来入侵的有害物种？