[Chika]

The earth in its entirety balances itself. Anyone that has taken a post High-School college course on environmental science would know this. Then you would also know that killing off one thing would cause an influx of another thing, that may not have been a problem in moderated numbers, but without any limitations, now become a problem. Like people who kill jumping spiders might as well open a jar of insects right in their bedroom.
Its easy not to apply critical thinking to life though, when a problem is not viewable to arise in the near future. This, one would/should have learned in Psychology 101.