Energy and ecology: why societies really succeed and fail

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An enlightening and informative essay on the longevity and viability of societies as a function of population and land usage: http://www.energybulletin.net/node/47833

Why do societies collapse? The apparent or proximate reason is often social strife, either within a formerly cohesive social group, or actual open warfare with an external enemy. But, all complex, urbanized societies are ultimately dependent upon agriculture; no army fights for long without food. In fact the Mayans, who had no pack animals and therefore no way to transport large quantities of food, would periodically break off battles to return home and harvest corn. This agricultural base is in turn dependent on the ecological health of the home environment, especially on fertile soil and adequate water. Thus the ultimate cause of collapse is often the deterioration of the ecosystems that feed human societies.

If you're still interested after reading this essay, you might want to read a few of Dr. Jared Diamond's works. He attempts to explain in detail why certain societies have advantages over others as well as why they collapse.

Here's a video documentary based on one of his books:
http://video.google.com/videoplay?docid=-4008293090480628280&ei=Wq-ISYvtEJXYqAPgnum6Cg&q=jared+diamond