A love of backcountry skiing explains David Gonzales’ obsession with white bark pines. A writer and photographer, he spends a lot of time beneath these ancient trees. But the white barks are under attack. And that has this skier marshaling forces to fight back. Once the snow melts, he leads volunteers called Tree Fighters into the forest surrounding Yellowstone National Park. Tree Fight is an organization that is working to curb the loss of white bark pines due to the escalating impact of climate change. Scientists say rising temperatures have opened the door to a mountain pine beetle invasion. White barks live at the highest, harshest elevations in the northwestern United States and Southwestern Canada. Extremely cold temperatures used to keep this native pest at lower elevations. Now these beetles are capitalizing on warmer temperatures, killing white barks at a staggering rate. Tree Fight aims to stop them.