reminds me of the fertile crescent. it used to be fertile, and now it's all shitty land, apparently because people did too much irrigation on it and made the earth salty. come to think of it, i remember there being salt crusts on irrigation channels in a few moroccan towns i visited. it's funny how such a little thing as salt can move the world, and there's surely nine dozen economic-ecologic phenomena that behave in just such an exhaustion-decline-replenishment-increase cycle.

I'm gonna be a good marxist and argue with you, however: why *wouldn't* resource depletion be a factor in civilization decline? i mean, civs are highly dependent on resources to support the level of division of labour that makes them, well, civs!