Studies: A Little Warming Can Destroy Societies

May 24 -- Throughout human history, civilizations have risen and collapsed as though their fates were written in the wind.

Now it turns out that maybe it wasn't the wind, but rain.

More than 11 centuries ago, the Mayan people of Central America built great cities with magnificent stone temples, developed hieroglyphic writing, and created beautiful works of art. And then their culture disintegrated.

To the north, the Anasazi Indians built multi-storied housing complexes and carefully structured communities in what is now the American Southwest before their civilization folded more than 700 years ago.

From the Middle East to Asia, other cultures rose and fell, and experts who have wondered why are finding a common thread in many of those amazing stories. It appears that drought has repeatedly played a major role in the collapse of societies that had, for a while at least, been at the apex of human civilization.

It's simplistic to say that rain — or the lack of it — has caused the demise of any complex society, because many forces were undoubtedly at work, but a growing body of scientific evidence now suggests that changes in the weather played a bigger role than had been thought.

Doesn’t Take Much

The findings are particularly significant during a time of great concern over evidence that the Earth's climate is changing once again, most likely because of human activities. Even subtle changes on a global scale — say a slight rise in temperature — are likely to cause dramatic changes in isolated areas, according to experts who have looked closely at the data.

For example, it may have taken nothing more than an almost immeasurable increase in solar radiation to bring down a sophisticated society, according to geologists at the University of Florida who have spent years studying the collapse of the Maya.

The researchers, led by geology professor David Hodell, found evidence several years ago that the Maya were hit by a prolonged and miserable drought about 750 A.D., just as their culture began to hit the skids. The researchers based that conclusion on core samples taken from the bottom of Lake Chichancanab on the north central Yucatan Peninsula in Mexico.