Megadrought in U.S. Southwest: A Bad Omen for Forests Globally

From Environment 360:  http://e360.yale.edu/feature/megadrought_in_us_southwest_a_bad_omen_for_forests_globally/2665/

Scientists studying a prolonged and severe drought in the southwestern U.S. say that extensive damage done to trees in that region portends what lies in store as other forests worldwide face rising temperatures, diminished rainfall, and devastating fires.

by Caroline Fraser
20 Jun 2013

As brutal fires torch tinder-dry dense forests and neighboring homes in the American West, researchers are examining the relationships between drought, wildfire, and a warming climate, predicting mass forest die-offs and prolonged megadrought for the Southwest. These forces are accelerating, they say, and already transforming the landscape. Unchecked, they may permanently destroy forests in the southwestern U.S. and in some other regions around the world.

Across the West, “megafires” have become the norm. With climbing temperatures, after a century of fire suppression, the total area burned has tripled since the 1970s, and the average annual number of fires over 10,000 acres is seven times what it was then. Fighting and suppressing fires costs more than $3 billion a year, not to mention lives lost. So understanding what, if anything, can be done to reduce intense forest fires has assumed an urgent priority.

Currently suffering the worst drought in the U.S., New Mexico has emerged as a “natural experiment” in megadrought, a laboratory for understanding drought’s deep history in the region — and what might lay in store in an era of rapid, human-caused warming.

With a highly variable climate, the Southwest boasts perhaps the best-studied megadrought history in the world. It’s the home of dendrology, the science of studying tree-rings, first developed at the University of Arizona. The pronounced seasonality of hot summers followed by cold winters produces well-defined rings, while archaeological fascination with Southwestern cultures — Chaco Canyon, Mesa Verde, and other sites where ancient peoples flourished and disappeared — has supported the collection and study of centuries of tree-ring data. Temperate-zone trees lay down wider rings in wet years, which narrow or vanish during drought. What’s more, rings can be precisely dated, with sets matched against each other, revealing burn scars and patterns of climate, precipitation, drought stress, and tree mortality.

Continue reading at:  http://e360.yale.edu/feature/megadrought_in_us_southwest_a_bad_omen_for_forests_globally/2665/

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