but ecosystems being robust is something i'll agree with you. since most natural ecosystem have to power to remove most toxins and create a livable atmosphere there are a lot more robust than most ppl think. though, there are always exceptions and most of the ecosystem processes takes a lot of time.
though... if u disrupt the ecosystem and ruin the environment. i think that's when the problems start to arise. in which case companies have played a major part with and not just with deforestation but with mining and oil drilling (thats a big one). both of these act not just disfigure the environment by polluting and destroying the vegetation and can lead to disruptions in the ecosystem from the interaction of the release toxins. but i'll admit most companies these days have started to clean up there act and have employed more environmental friendly approach.