There are numerous cases of foreign species competing with native organisms for food, and their lack of natural enemies may lead to ecological imbalances.
外來種與本地生物競食、缺乏天敵導致生態改變，甚至把本地生物吃掉，造成生物絕跡等破壞屢見不鮮，福壽螺就是最好的例子。