The first item on the framework is to look for human impacts on the envi- ronment: people inadvertently destroying the resource base on which they depend. [...] A second item on my checklist is climate change. Climate can get warmer or colder or dryer or wetter. [The climate] isn’t necessarily fatal. [...] The third thing on my checklist is relations with neighboring friendly societies that may prop up a society. And if that friendly support is pulled away, that may make a society more likely to collapse. [...] The fourth item on my checklist is relations with hostile societies. [...] And then finally, the fifth item on my checklist is the political, economic, social and cultural factors in the society that make it more or less likely that the society will perceive and solve its environmental problems.