Positive feedbacks are one of the most worrisome aspects of climate change. Viscious spirals could make controlling the problem far more difficult and, if we wait too long to act, potentially impossible to deal with. A new article in Nature suggests that the pine beetle epidemic in British Columbia has turned the forests there into net carbon emitters:
In the teamâ€™s model, a pine forest untouched by beetles but with a normal amount of logging is a slight carbon sink, sucking up more carbon (as carbon dioxide) than it loses (either as carbon dioxide or as timber). The only exception to this is when forest fires convert the forest to a net source, as they did in 2003. The beetles have an even bigger effect â€” in their worst year releasing 50% more carbon than the 2003 fires â€” and act over longer time scales, with additional logging making things even worse.
According to Werner Kurz, Natural Resources Canada’s senior research scientist, the total emissions associated with the outbreak will be about 990 megatonnes by 2020 – about 1.5 years worth of total Canadian emissions at present levels.
Eventually, the pine beetles will find themselves in the position of having nothing left to eat and the epidemic will taper off. What is nevertheless suggested by this situation is the possibility that climate change can lead to degraded ecosystems which hold less carbon dioxide, thus further contributing to climate change.