Genghis Khan, Vikings, and the Maya

A new book says we should blame weather rather than warfare for the collapse of Amerindian civilizations.

Climate Change?  Been There, Done ThatLonger summers and milder winters in Europe, especially stable from 1100 to 1300, allowed Norse explorers to range as far as Greenland and Labrador. At the same time a population boom in the rest of Europe led to radical deforestation, as trees were cleared to create farmland. By the end of the Medieval Warm Period half the forests that covered four-fifths of Western and Central Europe in A.D. 500 had disappeared.

Across vast swaths of the globe, however, severe, persistent droughts lasted not just for years but for generations. The Sierras of modern-day California experienced the severest droughts of the past 4,000 to 7,000 years. Acorn trees died, and along with them peoples largely dependent on acorns for food. Although data remain sketchy, it seems probable that extended droughts dried up pastureland on the Central Asian steppe, propelling the armies of Genghis Khan westward.

In the southern Yucatan arid conditions proved too much for the elaborate reservoirs, called “water mountains,” that the Maya used to irrigate their fields. Mr. Fagan permits himself an ominous aside: “The analogies to modern-day California, with its aqueducts for water-hungry Los Angeles, or to cities such as Tucson, Ariz., with its shrinking aquifers and falling water table, are irresistible.”The implications for modern society:The causes of the Medieval Warm Period remain unclear, and there is debate over what the actual temperatures were. Mr. Fagan draws one unambiguous conclusion from the evidence, however, in a final chapter on the present-day implications of the great warming of a thousand years ago. Drought is the great enemy, “the silent and insidious killer associated with global warming,” he writes.

Population density has placed enormous pressure on increasingly scarce water resources. As a result modern droughts, brought on by El Niño events, have taken an enormous toll in lives and wreaked measureless economic devastation. Prepare for worse.

“Judging from the arid cycles of a thousand years ago, the droughts of a warmer future will become more prolonged and harsher,” Mr. Fagan writes. “Even without greenhouse gases, the effects of prolonged droughts would be far more catastrophic today than they were even a century ago.”

For a spark of hope Mr. Fagan offers the example of Chimor, a kingdom in coastal Peru tormented by El Niño flooding and severe droughts throughout the Medieval Warm Period. The Chimu people thrived nonetheless by diversifying their food supply and protecting their scarce water resources. In a historically arid region with uncertain food supplies, they successfully tapped their centuries of experience with irrigation, soil conservation and water management. Look no further for a global-warming role model.Comment:  So a single climatological phenomenon may have been responsible for the rise of Genghis Khan, the Viking exploration of America, and the fall of the Maya, "Anasazi," and Khmer civilizations? Fascinating.

This tends to contradict the theories that say the Maya and Anasazi civilizations collapsed because of warfare. It's possible the droughts aggravated or even caused tensions that wouldn't have been fatal otherwise.

The Great Warming suggests the need for a more multicultural perspective. We need to learn from cultures such as the Chimu and Hopi about living within our means and conserving our resources. We should be imposing the actual costs of land development, water and energy usage, and environmental pollution so they don't overwhelm the ecosphere and lead to the collapse of our civilization.

For more on the subject, see Ecological Indian Talk.