Smoke as well as dust is spoiling the southwestern skies. As deBuys points out, forest fires are getting much bigger. In June 2002 the Rodeo and Chediski fires erupted on Arizonas Mogollon Plateau, soon merging into a single conflagration that consumed nearly 500,000 acres. It was Arizonas largest fireuntil the Wallow Fire eclipsed it in June 2011. Another devastating effect of climate change has been the explosion of bark beetles among western pines, which in turn contributes to the new fire regime; in 2003, dead trees covered 2.6 million acres in Arizona and New Mexico. Could anything be more demoralizing than the sight of green forests turned a grisly brown, then bursting into flame and left charred and black?
Even more depressing than declining forests are mountains bare of snow. When future springs arrive, the sound of running water will be much diminished. The biggest environmental catastrophe for the Southwest, already our most arid region, is losing the melting runoff from snowpacks into rivers, canals and irrigation ditches. An ominous chapter in the book examines the future of the Colorado River, which for decades has been the blood of the Southwests oasis civilization. In the 1920s Americans divided the river between upper and lower basins, allocating to each a share of the annual flow. California, which contributes almost nothing to the river, sucks up the largest share of any state, spreading it across the Imperial Valleys agricultural fields and diverting the rest to Los Angeles. Years ago policy makers assumed that the river carried about 17 million acre-feet of water per yearthat is, enough water to cover 17 million acres to a depth of one foot. They overestimated, as people tend to do when hope and greed outrun the facts. Now comes a drier and hotter future, when the Colorado River will carry even less waterperhaps as little as 11 million acre-feet.
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2016-02-26
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