Human beings have built cities, bridges, canals, roads. We have connected an entire planet once seperated by nature. We have raised forests, fields, and herds of animals. We have domesticated plants and animals into species larger, tastier, and easier to grow. All that we have built has been to improve nature, to tame wilderness. People complain about humans hurting nature, but it is only by taming nature that humans could get to a point where they could appreciate her beauty. The earth exists for humans.
Humans have caused global warming on a large scale. At this point we are nearing a turning point that will end our ability to fix the damage we have caused. The more we near this tipping point without fixing it, the more likely that we will be unable to fix it. While we are damaging Earth, we are also severely ruining our ability to live on it, as well as ruining it for other species as well.
Not all humans have made the Earth a worse place. There are simply too many of us and that has put a strain on the natural balance of the planet. The difficulty is that humans upset the natural balance--all animals reach some kind of tipping point where their population can no longer be supported and the population plummets. Humans, unless something is done to control our numbers, will face the same crisis sometime in the future.