What are you talking about? Humans have already irrevocably altered the natural ecosystem over the past 100k years. We have: killed off all the megafauna, domesticated thousands of plants, drastically changed the landscape through agriculture, literally changed the courses of rivers, diverted water all over the planet, etc. And that was all before the modern era.
Sure, this sounds reasonable, but it's really not when you look at the magnitudes of our impact over time. It's clear that the actions of the last 50-100 years or so are in extreme excess of what can be stabilised by the global weather and ecological systems. We've gone from about two thirds remaining natural wilderness in the world in the early 1900s to one third remaining today. The continued survival of most species, including ours, is very much in danger if we don't reverse a lot of this.
