I'd certainly believe that ecological stress could be a contributing factor. Perhaps civilizations that are already weak for other reasons like corruption, demo

I'd certainly believe that ecological stress could be a contributing factor. Perhaps civilizations that are already weak for other reasons like corruption, demographics, etc. are unable to innovate, adapt, substitute resources, or otherwise adjust when confronted by ecological stress. There's a thesis on the collapse of Rome that argues that a volcanic eruption helped tip it over: https://www.nytimes.com/2020/06/22/science/rome-caesar-volcano.html https://www.nytimes.com/2020/06/22/science/rome-caesar-volca... Not self-inflicted, but still ecological. But Rome was already weak when it occurred.