Environmental Trends 2007

The Mountain Pine Beetle in British Columbia

Photo credit: Ministry of Forests and Range

Forests in interior B.C. are experiencing the largest mountain pine beetle outbreak ever recorded in the province. The mountain pine beetle (Dentroctonus ponderosae) attacks mature pine trees and lays eggs under the bark. When the eggs hatch, the beetle larvae feed on the inner bark, spreading a fungus, which cuts off the tree’s nutrient supply and eventually kills the tree. The needles of dying trees turn red and then grey, leaving a pattern of green, red and grey trees in the forest.

Why is it happening?

Mountain pine beetle has always been a natural part of B.C.’s pine forest ecosystem, but cold winter temperatures have kept its numbers in check. The environment has become much more favourable for the beetles in recent years because:

  • due to global warming, the mild winters have not been cold enough to kill over wintering beetles in the trees, and
  • due to fire suppression efforts, there are now three times more mature lodgepole pines in interior forests than there were a hundred years ago.

As of 2006, about 20 per cent of the province’s total forest area was affected by mountain pine beetle.

Source: Ministry of Forests and Range

About 40 per cent of the saleable pine in the province has likely already been killed. The timing of the peak infestation varies in different areas, but on a provincial scale, the worst year of the infestation was 2004. Since then, the volume of pine killed each year has declined. The infestation is projected to continue causing significant damage until about 2009 and then subside rapidly. By 2018 when the infestation is projected to have run its course, over 78 per cent of the mature pine will have been killed, affecting over one third of the total area of B.C. forests.

Losing the mature forest canopy reduces the habitat for squirrels, martin, fisher and many birds. It also reduces the winter cover for ungulates, such as deer, elk and moose. However, the large number of dead trees provide habitat for woodpeckers and cavity nesting birds and new understory vegetation benefits ruffed grouse and improve summer forage for ungulates and bears.

More Information