As anyone who has taken any elementary biology course should know, the world is an entangled web of interrelationships between organisms and the environment in which they live. There is no plant, insect animal, or bacteria which does not have a crucial role to play in the balance of nature. Some change made in any one of the myriad parts of the whole can set the entire system off balance, creating a new system with a different balance, which can in many instances spell disaster for some of the parts. Unless one is willing to risk harming some part of the system, be it animal, mineral or vegetable, it is best not to interfere.
One famous example of a simple system which was interfered with at the cost of worse results was the case of the city that had a bad problem with stray cats. The city decided it was dangerous, unsightly and unhygienic to have so many stray cats around. The city managed to get rid of all their cats one way or another, and suddenly they had a much worse problem on their hands; the population of rodents, rats and mice, soared. Unbeknownst to the townspeople, the cats had been keeping the rodent population to a minimum. Now, without the cats, the people had to face the much worse problem of rats roaming around.
The lesson is that every ecosystem has a balance which took years to arrive at, and any tampering is bound to result in a change, which could easily be worse than the problem which was attempted to be solved.