Why More than 100 Million Trees Have Died in the Sierra Nevada

The Sierra Nevada mountains are home to 300-year-old ponderosa pines, but according to Bettina Boxall's reporting in the Los Angeles Times, the drought and beetles are killing of many of the oldest trees. "The U.S. Forest Service estimates that since 2010, more than 102 million drought-stressed and beetle-ravaged trees have died across 7.7 million acres of California forest." Boxall writes. The majority of this die-off happened last year. "The western Sierra pine forest as it was 100 years ago is not coming back," Boxall reports.

The stress from the drought left the pines vulnerable to beetles, which ultimately kill the trees. "Western pine beetles’ squiggles mar the tan inner bark, or phloem, where the dark brown females had tunneled and laid their eggs," Boxall writes. In an increasingly warm world, ecologists say the damage is unlikely to ever be reversed.