Many people still hold stubbornly to a belief that nature's resources are unbounded, that the world's ecosystems are simply too large to be significantly impacted by the mere actions of humans. But in fact, man-made environmental catastrophes have occurred throughout human history, and have even caused the collapse of whole civilizations. Long before the boons of modern industry and technology, humans have wrought environmental destruction with much less. As a stark reminder of that lesson, here's our list of nine ancient environmental catastrophes caused by people. (Text: Bryan Nelson)