SOURCE: Yale e360
DATE: September 21, 2017
SNIP: “The amount of conifer mortality that we’re seeing both here and in Europe is unprecedented historically,” says Jesse Morris, a geographer with the University of Utah in Salt Lake City. Morris and other scientists are trying to determine the potential impacts, such as more intense wildfires, disrupted watersheds, destroyed habitats, and reduced carbon storage, as climate change spurs increasingly widespread and severe beetle outbreaks.
Bark beetles are a natural part of the conifer forest life cycle, regularly flaring and fading like fireworks. But the scope and intensity in the past two decades is anything but normal, scientists say, in large part because rising temperatures are preventing the widespread winter die-off of beetle larvae, while also enhancing the beetles’ killing power.
When beetles burrow into their bark, trees release a sap rich with volatile toxic chemicals to flush the insects and prevent them from sending pheromone signals mustering other beetles. But increasingly long and intense droughts of recent years have weakened the trees’ defenses. Without sufficient water, trees can’t produce enough sap. Hot temperatures cause further moisture loss. Trees weaken and become easier to overwhelm.