Trees tend to become more susceptible to spruce beetle infestations during especially dry periods, according to research from the University of Colorado. The reasons remain somewhat unclear, but researchers suggest that drought may weaken trees' natural defenses against pests. "From a historical perspective, when you look back over the last few thousand years, it's not just the warming. It's the drought that predisposes the trees to attack," geography professor Thomas Veblen said.
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