In the video below, Jared Diamond discusses the findings of his book Collapse.
The point of the book is best described by its subtitle: How Societies Choose to Fail or Survive.
It would take days or even weeks to read the 560 pages of the book, but in only an hour, Diamond provides an effective summary in the video below.
Diamond developed a five point framework for considering the fate of societies. The following paragraph, taken from page 11 of the book, briefly describes the factors:
... I don't know of any case in which a societie's collapse can be attributed solely to environmental damage: there are always other contributing factors. When I began to plan this book, I didn't appreciate those complications, and I naively thought that the book would just be about enviromental damage. Eventually, I arrived at a five-point framework of possible contributing factors that I now consider in trying to understand any putative environmental collapse. Four of those sets of factors - environmental damage, climate change, hostile neighbors, and friendly trade partners - may or may not prove significant for a particular society. The fifth set of factors - the society's response to its environmental problems - always proves significant.