Did Drought Help End Roman Rule?

Dec. 29, 2008 -- In a dripping, stalactite-filled cave outside of Jerusalem, geologists have unearthed clues about what happened to a bustling civilization more than a millennium ago.

The researchers used a new technique to figure out exactly how much rain fell in the Eastern Mediterranean between about 1,000 and 2,000 years ago. In some stretches, the scientists were able to pinpoint what the region's weather was like from one week to the next -- by far the most detailed climate history ever produced.

The results showed a gradual drying between about 100 and 700 A.D., with sharp drops in rainfall at 100 A.D. and 400 A.D. Overall, annual rainfall fell 50 percent during those centuries, dropping from an average of more than 3 feet per year to 1.6 feet.

During the same period, Roman rule declined in the area. This is the first study to link the two events.

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"Such a large change in rainfall may have played an important part in the historical events that took place in that region at that time," said Ian Orland, a Ph.D. candidate in geology at the University of Wisconsin, who co-led the study.

As their crops suffered, the Romans probably began to struggle until finally succumbing to the growing Islamic empire at the Battle of Yarmouk in 636 A.D.

The new insights were especially surprising because the scientists weren't expecting to find anything interesting. Their study began simply as an attempt to test the capabilities of a tool called an ion microprobe.