6. Forestry in British Columbia
Case Study 1: Mountain Pine Beetle
The mountain pine beetle (Dendroctonus ponderosae) is a species of bark beetle native to the forests of western North America. It has a hard black exoskeleton and measures approximately five millimetres in length, about the size of a grain of rice.
The current outbreak of mountain pine beetle in British Columbia began in the early 1990s and is considered to be the largest ever recorded, affecting over 18.1 million hectares, or an area five times the size of Vancouver Island.
The mountain pine beetle infestation has had a devastating effect on the forest of British Columbia and has killed about 50% of the total volume of commercial lodge pole pine in the province.
In British Columbia, the infestation peaked in 2005 and has been decreasing each year as the amount of available mature pines decreases. In 2012 about 3 million hectares of BC forest was designated as red-attack, which is where the needles of infected trees turn red as a result of the beetle killing the tree. This is down from 2011 when the amount of red-attack forest was 4.6 million hectares.
Causes of the Infestation
Scientists believe that warmer summers and milder winters play an important contributing role to the beetle infestation. Cold Canadian winters with temperatures below -40°C normally kill the beetle as well as pine beetle eggs and larvae. But milder winters and warmer summers have meant more beetles survive the winter. Until recently, it was believed that the mountain pine beetle could successfully attack only mature pine trees, but in recent years it has started to attack younger trees.
Increased Fire Hazard
It is believed that large areas of dead pine stands represent a potential fire hazard. The BC government is addressing this concern by directing fuel management activities in beetle areas as recommended in the 2003 Firestorm Provincial Review. Harvesting the affected stands of trees aids fire management by removing the presumed hazard and breaking the continuity of the fuels. These fuel management treatments are specifically designed to reduce interface fire threats to communities located in the infestation zone. (The interface is the area where urban development and wilderness meet.)
Life Cycle and Pine Tree Infestation
Beetles develop through four stages: egg, larva, pupa and adult. Except for a few days during the summer when adults emerge from brood trees and fly to attack new host trees, all life stages are spent beneath the bark.
In low elevation stands and in warm years, mountain pine beetles require one year to complete a generation. At high elevations, where summers are typically cooler, life cycles may vary from one to two years.
It is the female beetle who initiates an attack. As they chew into the inner bark and phloem (the living tissue that carries organic nutrients), pheromones are released, attracting male and female beetles to the same tree. The attacking beetles produce more pheromones