As much as I enjoyed his books, I thought he had gone a bit nuts by the time he wrote his latest one on collapsing societies. Too much time in the jungle without wearing a hat.
Read the transcript here, or listen to the podcast, to get an alternative view.
My favourite bit about why Easter Island has no forests - nothing to do with erecting all those enormous heads. When the Polynesians arrived, they brought rats with them. The rats had no predators on Easter Island, so they went forth and multiplied - to plague proportions perhaps? The rats feasted on the seeds of the pine trees, so no more baby pine trees. As the people cleared the land for agriculture etc and moved on, the forest did not grow back thanks to the rats.
Population collapse - nothing to do with eco-suicide. In 1722, a Dutch ship arrived and various European plagues quickly did most of the population in.
In short, Diamond tells good fairy stories that sell well.