Three stages of trees killed by bark beetles. Top: dead needles, Bottom: dead standing trees in background, fallen trees in foreground. Huge swathes of such damage can be seen in the American West from Alaska to Arizona. The winters are warmer, allowing various species of beetle to survive and multiply. The dead trees, along with warmer and drier summers, have brought a rapid increase in forest fires.

These photos were taken in 2010 in the Wind River Range in Wyoming, where I have backpacked for many years. I first saw beetle damage there in 2008; it has been spreading rapidly.

SEE ALSO Threatened ecosystems
Photos ©2010 Spencer Weart.