From the Washington Post:
The death rates of trees in Western U.S. forests have doubled over the past two to three decades, according to a new study spearheaded by the U.S. Geological Survey, driven in large part by higher temperatures and water scarcity linked to climate change
Nathan L. Stephenson, one of the lead authors, said summers are getting longer and hotter in the West, subjecting trees to greater stress from droughts and attacks by insect infestations, factors that contribute to tree die-offs.
“It’s very likely that mortality rates will continue to rise,” said Stephenson, a scientist at the Geological Survey’s Western Ecological Research Center, adding that the death of older trees is rapidly exceeding the growth of new ones, akin to a town where the deaths of old people are outpacing the number of babies being born. “If you saw that going on in your home town, you’d be concerned.”
The recent warming in the West “has contributed to widespread hydrologic changes, such as a declining fraction of precipitation falling as snow, declining water snow pack content, earlier spring snowmelt and runoff, and a consequent lengthening of the summer drought,” they wrote.
The scientists said it was hard to predict how the changes would transform the Western landscape, although they anticipated that in the future the West will boast sparser forests that cannot store as much carbon as they do now, which could contribute to further warming.
This is yet another symptom where subtle climate shifts damage the natural negative feedback in the carbon cycle, which further accelerates the climate changes. There has recently been a whole spate of reports about how the ocean’s ability to absorb carbon is beginning to decline as it becomes saturated, cleaning up after mankind’s profligate use of fossil fuels. But that’s for another post. An article appears in today’s Sunday Star Times regarding the tree deaths, but is not available online.