Trees affected by mountain pine beetle.

Photo of lodgepole pines killed by mountain pine beetle near the Snake Indian River in Jasper National Park. Broad patches of dead pine trees with rusty red needles are interspersed in the landscape with bright-green patches of living deciduous forest.
Bark beetles only attack coniferous trees (the patches of green are healthy aspen and spruce trees not affected by the insects). The beetles are native to mountain forests, but can have a greater impact when trees are stressed by drought and climate change.