What the West’s Ancient Droughts Say About Its Future

18 Mar, 2014 - By

A millennium ago—just yesterday, in geologic time—Native Americans waited all winter for rains that never came. They waited the next winter and the next. Then the marshes of their sacred San Francisco Bay turned from cattails to salt grass. Fishing declined and the Native Americans could no longer rely on the bounty of the bay. Finally, they left, hungry and thirsty, in search of water.

Now, as modern Californians hope for fierce storms to break a dangerous dry spell, the questions arise: Is the current drought just an aberration? Or might it signal the beginning of a more fearsome era, with echoes of the ancient drought that uprooted Native Americans? Is it a megadrought?

Most scientists sidestep a yes or no answer. But they agree that the past century has been unusually moist—and warn that California is now vulnerable to a drought that is measured not in years, but decades. Perhaps even centuries.

On a trip to California’s Central Valley on Friday, U.S. President Barack Obama is expected to link the drought to climate change and to announce federal aid aimed at “climate resilience.”

But ancient clues in the landscape show this is not the first time the American West has been severely parched. It’s unlikely to be the last. And the recent spate of dry years is nothing next to the ancient “megadroughts” that have occurred multiple times in human history. “What research shows is a roughly 50- to 90-year cycle of wet and dry periods over the last few thousand years, with some droughts lasting over a decade. But between 900 and 1400 A.D., during the‘Medieval Warm Period,‘ there were a couple of droughts that were over a century long,” said B. Lynn Ingram, professor of Earth and planetary science and geography at the University of California, Berkeley, and co-author of the book The West Without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us About Tomorrow.

“The 20th century was a relatively wet time, and a time when all of our modern societies were built,” she said. “We’ve had centuries where it was far drier. We’re not prepared.”

 

http://news.nationalgeographic.com/news/2014/02/140214-drought-california-prehistory-science-climate-san-francisco-2/


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