Leave your feedback Share Copy URL https://www.pbs.org/newshour/show/scientists-see-more-risk-of-wildfires-with-forest-changes Email Facebook Twitter LinkedIn Pinterest Tumblr Share on Facebook Share on Twitter Transcript Scientists are already witnessing climate change increase the threat of wildfires, as warmer temperatures drive more beetles to the forest, where they in turn kill trees and make the woods more susceptible to catching ablaze. Heidi Cullen of Climate Central reports. Read the Full Transcript Notice: Transcripts are machine and human generated and lightly edited for accuracy. They may contain errors. JIM LEHRER: Now a second story about wildfires in the west. It's about warming trends.The reporter is Heidi Cullen, a climatologist and correspondent for Climate Central, a nonpartisan research group of journalists and scientists. HEIDI CULLEN: This entire forest east of the Cascade Mountains has been put at risk by tiny pine beetles eating their way into the tissue of trees.DR. SUSAN PRICHARD, forest ecologist, University of Washington: I find it amazing that such a small, nondescript little beetle can wreak such havoc on forest systems. HEIDI CULLEN: Susan Prichard studies beetles as a forest ecologist at University of Washington. DR. SUSAN PRICHARD: Each one of these yellow sap concentrations is an actual site where a mountain pine beetle has bored into the bark of the lodgepole pine. And then it will lay eggs and its larvae will actually feed on the cambial tissue, the living tissue of the tree.So, here, each one of these centers is an example of the tree trying to pitch out the beetle. The actual sap of the tree has resins that are toxic to the beetles, and then, also, they physically push the beetle out of the tree. HEIDI CULLEN: Wow. So, this tree is literally just fighting for its life. DR. SUSAN PRICHARD: It is fighting for its life. HEIDI CULLEN: Beetles thrive in warm weather. Milder winters, earlier springs, and longer summers mean more beetles. DR. SUSAN PRICHARD: So there is a climate link with mountain pine beetle, for sure. And what we're noticing in Washington State, even today, that, in the last 20 years, with warmer climate, warmer documented climate, there has been an increased incidence of mountain pine beetles. HEIDI CULLEN: Prichard and other scientists say, if the beetles kill enough trees, eventually, more and more of the forest is vulnerable to intense wildfires. DR. SUSAN PRICHARD: And, in the late 1990s, a predictable event occurred. Mountain pine beetle started to have a large outbreak. And, after the outbreak occurred, over about 10 years, there were accumulations of both dead spruce from spruce beetle, and dead lodgepole pine from mountain pine beetle that were susceptible to a big fire event.