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Southwestern trees will dwindle with climate change

Tiffany Stecker, E&E reporter

Published: Wednesday, October 3, 2012

In the next 50 to 70 years, the landscape around the breezy mountain city of Santa Fe, N.M., will look more like hot, arid Albuquerque.

So says the lead author of a new study in  Nature Climate Change, which finds that increased drought and changes in the region's climate will alter southwestern U.S. forests unlike anything that has been seen before.

"In the Southwest, the general rule is that the distribution of forests is dictated by drought," said A. Park Williams, a researcher in the Earth and environmental sciences division of the Los Alamos National Laboratory. "Where it's too dry, they don't grow. As the climate warms, the lower-elevation forests will be eliminated."

By the middle of the 21st century, even the mildest years of a drought will be hotter and drier than the harshest years of major droughts since A.D. 1200, the researchers found. Southwestern trees thrive when winter precipitation is high and summer and fall temperatures are relatively mild with moderate humidity.

The scientists created an index with tree ring data from hundreds of sites in the Southwest and compared the numbers with climate records dating back to 1896. The tree rings indicate signs of water stress, disease and insect infestations, which are more common in dry times.

"It's the first time that hundreds of tree rings records are put together," said Williams. "This is first time the region's story has been told."

Despite the harsh drought of the past century, there have been several "megadroughts" in the past thousand years. Two of the most severe droughts occurred in the late 1200s and the late 1500s.

According to findings, the megadroughts of centuries past will be regular events by the middle of this century. The extremes will be wider, as well: Drought stress levels, even in the wettest and coolest years after 2050, will be worse than the driest, warmest years of the megadroughts of years past.

Return of the megadroughts

The megadrought of the 13th century is said to have left a significant impact on the native Puebloan culture, as many villages were abandoned in this period. Research has also indicated that drought played a role in the demise of ancient Aztec and Toltec cultures in Mexico, according to a study from last year (ClimateWire, Feb. 8, 2011).

Recent research has found that drastic droughts will become regular occurrences by the end of the century (ClimateWire, July 31).

"[This study] shows that the impacts on the forests will not be restricted to one species or one site at low elevation, but in fact will take place at forests across the landscape," said Daniel Griffith, a co-author and a researcher in geography at the University of Arizona.

This research could provide forest managers with information on how to maintain forests better, including preliminary guidance on how to thin forests to reduce the risks of wildfires.

"What we're seeing in recent years are monster-sized wildfires taking out chunks of forests," said Williams, "forests we wouldn't have expected to [be damaged by] climate change."

"As climate changes, it's going to be very important to us how we can shepherd forests into a new world," he added.


Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. www.eenews.net. 202-628-6500

 

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