""That's because trees don't just absorb carbon when they grow, they emit it when they die and decompose, or burn.

When you add up both the absorption and emission, Canada's forests haven't been a net carbon sink since 2001. Due largely to forest fires and insect infestations, the trees have actually added to our country's greenhouse gas emissions for each of the past 15 years on record.""

Also, something not mentioned in the article (but added by a botanist friend), conifers in general apparently produce much more volatile oils, so are more susceptible to flames/ignition/burning.