California Once Had a 2,000-Year-Long Dry Spell

posted: 10/02/15
by: Patrick J. Kiger for Discovery News
Lake Hume in drought
Tim J Keegan/Flickr

California's current lengthy drought is really punishing the state's residents, who've been compelled by government restrictions to reduce their water use by nearly a third in a desperate effort to conserve the dwindling amount of H2O left in the state's reservoirs.

But as a recently-published study in the journal Quaternary Science Reviews reveals, the state once experienced a much longer dry spell -- a series of mega-droughts as bad as the one today, strung together over a 2,000-year-period.

Fortunately, though, they occurred at a time -- 25,500 to 27,500 years ago -- when there weren't any Californians around yet to complain about not being able to water their lawns.

Paleoecologists Linda Heusser and Jonathan Nichols, of Lamont-Doherty Earth Observatory, did a high-resolution analysis of pollen levels in a sediment core drilled from the bottom of Lake Elsinore, which is to the east of the Santa Ana Mountains near Los Angeles. That method provides the first detailed continuous record of ecological changes in coastal southern California from 32,000 to 9,000 years ago, with shifts measurable on a scale of decades rather than centuries.

Pollen records are unique in that we can capture the vegetation distribution," Heusser said in a press release. "There are no other records of vegetation that extend through this time. The best we had been able to do before for this time frame was stalagmites inferring precipitation in a cave in New Mexico."

The pollen count at various levels of the sediment showed that pine trees and juniper, which dominated the region's ecosystem until about 27,500 years ago, were replaced by dryland herbs, shrubs and chaparral for about 2,000 years. Then, the pine trees and junipers began to return.

The researchers also found that changes in the pollen record also correlate with analysis of sediment cores from the Pacific Ocean just off Santa Barbara, which show that that the ocean was warmer during the periods that droughts occurred. That suggests that ocean conditions may have been the driver of the mega droughts.

This post originally appeared on Discovery News


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