In some areas of the Western states the 20-year long drought has reduced moisture content in plants to the lowest levels scientists have seen. Soil moisture is very low — at or near record lows across much of California. Particularly hard hit are locations in Colorado, Utah, Nevada, New Mexico, Arizona, and California.
Junipers are dying in Arizona from a lack of water. The East Bay Times reports that drought is likely responsible for dead or dying acacia, eucalyptus, and Monterey pines in East Bay Regional Parks near San Francisco.
From the an Associated Press article by Seth Borenstein:
In Arizona, junipers are succumbing to the 20-year drought and its two-year intensification, said Joel McMillin, a forest health zone leader for the U.S. Forest Service there. Officials haven’t done a precise count but anecdotally the die-off is 5% to 30% with some patches up to 60%.
Until the dead needles drop to the ground, which takes a year or so, the fire hazard increases, fire manager Steinhardt said. “So you have something that’s highly flammable and it’s … 20-, 30-, 40-foot tall and every single one of those needles on there now becomes an ember that can be launched.”
“This is probably one of the driest and potentially most challenging situations I’ve been in,” said the veteran of 32 fire seasons.
In California, normally drought-tolerant blue oaks are dying around the San Francisco Bay Area, said Scott Stephens, a fire science professor at the University of California, Berkeley. “They don’t have access to water. Soil moisture is so low. When you start to see blue oak dying, that gets your attention.”
Human-caused climate change and decades of fire suppression that increases fuel loads are aggravating fire conditions across the West, scientists said.
Global warming has contributed to the megadrought and is making plants more prone to burning.
Vegetation with a low moisture content is easier to ignite in a wildfire and contributes to a rapid rate rate of spread that is more difficult for firefighters to suppress. Dead or dying trees that still have leaves attached during the first year or so after their decline can also enhance the spread and intensity of a fire and adds to the number of burning embers lofted into the air that can ignite spot fires ahead of the blaze, putting structures at risk that are distant from the fire.
Extremely dry soil and vegetation in May does not guarantee a busier than average summer fire season in the West — the weather in the coming months is the primary factor. If it turns relatively cool and wet, the number of acres burned is not likely to be extreme. But if the drought continues into June, July, and August, normal weather, or especially warmer and drier than normal weather, could produce a busier than average Western fire season.