入侵物种

Why don’t we discuss a few more invasive species before today’s class ends? Now, although we’ve discussed a lot of harmful invasive species, please remember that they are not always detrimental to the local ecosystem. In fact, I could name a few that have actually been, well, beneficial. Don’t believe me? Okay, listen to this.

Everyone knows that Kansas is famous for wheat and Texas is celebrated for cows. Well, they are both, uh, invasive species. And they haven't done any harm to the environment. For example, wheat has not caused the extinction of any local wildlife. It doesn't use up an excessive amount of resources like some invasive species do. And cows, of course, are not predators, so no animals have been killed by them while they graze. Those are two examples of harmless invasive species. But how about invasive species that are, uh, beneficial? Yeah, it sometimes happens.

A perfect case is that of the Cane toad which was introduced for farmers down in Florida, among other places. Cane toads devour many harmful insects, so they keep the bug population down.Also, since the toads eat so many insects, farmers don't have to use any pesticides that could be dangerous to humans. So, cane toads are actually helpful to many people, showing that invasive species sometimes do have benefits.

我们为什么不在今天课程结束之前再多讨论一些入侵物种呢？现在，虽然我们讨论了很多有害的入侵物种，但请记住，入侵物种对当地的生态并不总是有害的。事实上，我可以说出一些对生态有益的物种。不信吗？好吧，听听这个。

众所周知. 堪萨斯州以小麦著称，而得克萨斯州以牛闻名于世。但是，它们都是入侵物种，却对环境没有任何害处。比如，小麦没有造成当地任何野生动植物的灭绝。它们并没有像其他一些入侵物种一样消耗过多的资源。而且，牛当然也不是捕食者，所以当它们吃草的时候并没有动物被它们杀害。

这是两个无害的入侵物种。但有益的入侵物种情况如何呢？是的，这样的事情有时也会发生。一个很好的例子是蔗蟾，一种被佛罗里达州和其他地方的农民引人的物种。蔗蟾吃掉了很多害虫，使得害虫的数量大大减少。而且，因为蔗螗吃掉了许多虫子，农民就不需要使用任何可能对人体有害的杀虫剂。因此，蔗赡实际上对很多人有帮助，这表明入侵物种有时候的确有好处。