Mountain Pine Beetle Damage — Mountain Pine Beetle Have Been A Natural Part Of The Whitebark Pine Forest For Many, Many Years. Their Population Size (and Thus The Severity Of Their Damage) Was Naturally Controlled By Extremely Cold Winter Temperatures. But Recently, Winter Temperatures Have Not Been Cold Enough To Kill The Beetles And Their Populations Have Increased. Whitebark Pines Also Used To Be Healthy And Vigorous Trees Because Of Ample Precipitation And Moderate Summer Temperatures. However, A Changing Climate Has Physiologically Stressed The Trees, Making Them Susceptible To Beetle Infestations. This On-two Punch Makes It Difficult For The Trees To Defend Themselves. At USGS, Researchers Are Monitoring The Health Of Productivity Of These Forests To Determine The Importance And Impact Of Changes In Pine Nut Production On Grizzly Bears In The Greater Yellowstone Ecosystem. Photo Credit: Don Becker, USGS Photo