When humans come to a new area it always changes the local ecology. The real question is the change good or bad or just a change. Today the North and South Islands of New Zealand are some of the most beautiful places on earth. I do not think humans hurt it unless one thinks anything humans do to change the environment is evil.
Case in point is the United Kingdom. Four thousand years ago it was forests with a few tribal areas. It was mostly untouched by the hand of man. Today it is a vibrant nation and the landscape has little resemblance to 4000 years ago. This is not bad, it is simply change.
I love watching the Time Team episodes on YouTube, they go to areas that look a lot like my own local landscape, and just as rural, yet I know that the population density is much higher there. OTOH, we don't have Roman roads across the terrain, and mosaics just under the grass. A little jealous.
Also, once in a while, those fecal sterols get flushed. :^)
Time Team Special 51 (2013) - Britain’s Stone Age Tsunami
https://www.youtube.com/watch?v=3EPNZWBk7i8
Tsunamis in the Alps? A killer wave slammed medieval Geneva, a new study says... [500 A.D.]
http://www.freerepublic.com/focus/chat/2953567/posts
In the same way, the Brazilian rain forest was once a vibrant human landscape of canals, farms, and fertile fields.
When most of the native Americans died off from Eurasian diseases (not done by Europeans on purpose), the land went back to jungle.