To take an example from last year, in an op-ed on Iraq in the LA Times (I can't find an online link, so this quote is from my copy), he talked about the decline of the Fertile Crescent (what we now call the Middle East and the cradle of civilization) and The erosion of Civilization
So how did Fertile Crescent peoples lose that big lead? The short answer is ecological suicide: They inadvertently destroyed the environmental resources on which their society depended. Just as the region's rise wasn't due to any special virtue of its people, its fall wasn't due to any special blindness on their part. Instead, they had the misfortune to be living in an extremely fragile environment, which, because of its low rainfall, was particularly susceptible to deforestation.
When you clear a forest in a high-rainfall tropical area, new trees grow up to a height of 15 feet within a year; in a dry area like the Fertile Crescent, regeneration is much slower. And when you add to the equation grazing by sheep and goats, new trees stand little chance. Deforestation led to soil erosion, and irrigation agriculture led to salinization, both by releasing salt buried deep in the ground and by adding salt through irrigation water. After centuries of degradation, areas of Iraq that formerly supported productive irrigation agriculture are today salt pans where nothing grows.
Once the Fertile Crescent began to decline for those environmental reasons, hostile neighbors helped speed the process. The original flow of power westward from the Fertile Crescent reversed in 330 BC, when the Macedonian army of Alexander the Great advanced eastward to conquer the eastern Mediterranean. In the Middle Ages, Mongol invaders from Central Asia destroyed Iraq's irrigation systems. After World War I, England and France dismembered the Ottoman Empire and carved out Iraq and other states as pawns of European colonial interests. As the end product of this history, the former world center of wealth, power and civilization is now poor in everything except oil. Iraq's leaders ensured that few benefits of that oil reached their people.
Iraq's decline holds a broader significance. Many other countries today face similar crippling environmental problems, including the deforestation, overgrazing, erosion and salinization that brought down the Fertile Crescent. Other countries already crippled or nearly so by such problems include Haiti, Somalia, Rwanda, Afghanistan, Pakistan, Nepal, the Philippines and Indonesia.
You may well detect a similarity between this list of looming environmental disasters and the CIA's list of overseas trouble spots, places prone to civil wars and violent regime changes ? places to which we often end up dispatching U.S. troops. Those two lists are related by cause and effect. When environmental damage makes people economically desperate, they are likely to suffer from poor health and short life spans, blame their governments, kill each other, end up with crazy leaders and seek to immigrate illegally to more favored landscapes.
Or for a more extensive treatment in a recent take on Why Societies Collapse, consider this excerpt from a speech
If one asked an academic ecologist to name the countries in the modern world that suffer from most severe problems of environmental damage and of over-population, and if this ecologist never read the newspapers and didn't know anything about modern political problems, the ecologist would say "Well that's a no-brainer, the countries today that have ecological and populations, there are Haiti, Somalia, Rwanda, Burundi, Iraq, Afghanistan, Pakistan, Nepal, the Philippines, Indonesia, Solomon Islands." Then you ask a politician who doesn't know, or a strategic planner who knows or cares nothing about ecological problems, what you see is the political tinderboxes of the modern world, the danger spots, and the politician or strategic planner would say "It's a no-brainer; Haiti, Somalia, Rwanda, Burundi, Iraq, Afghanistan, Pakistan, Nepal, the Philippines, Indonesia, Solomon Islands", the same list. And that simply makes the point that countries that get into environmental trouble are likely to get into political trouble both for themselves and to cause political troubles around the world...