There was more vegetation in the past
It's indisputable that there was more vegetation at times in our distant past. Coal is thought to have formed 400 million years ago from vegetation on land, and we're not producing significant amounts now. Oil formed from plant and animal life in the shallow seas of 200 million or so years ago. It's believed that during these times the earth was as much as 7 degF hotter than it is now, which is about double the rise expected this century.
Global warming, whether man-made or not, will not destroy life on this planet. It may even result in more life than we have now. But it will require massive adjustments by humans. However, if you look at the changes in civilization during the past 200 years or so, it's clear we can do it if we need to.
