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Southwestern forests threatened by heat and lack of moisture

Climate Central published an article last week describing the devastating 2011 wildfire season in the Southwest.  The widespread fires can be attributed in part to warmer temperatures but are also related to lower humidities, since warmer air has the potential to hold more moisture than cooler air.  In the article the author points out that the conditions in 2011 are similar to what climate models project for future climate in the Southwest  by 2050.  One of the scientists quoted, Park Williams of the Lamont Doherty Earth Observatory, said that while Southwestern forests are likely to survive, they may not look at all like what those forests are today.  A related technical article by Williams in the Journal of Applied Meteorology and Climatology describes the importance of vapor pressure deficits in setting up conditions that are ripe for wildfires (abstract available here).

A separate article this week in Yahoo News pointed out that a study in Proceedings of the National Academy of Sciences has shown that California’s forests are losing their big trees.  Recent changes to a drier and hotter climate have favored the growth of smaller trees like oak.  The study showed that the greatest loss of trees came in areas with the greatest moisture stress, particularly in areas that have decreasing snow pack.

Source: USDA via Flickr

Source: USDA via Flickr