Wednesday, January 23, 2013
According to the draft US National Climate Assessment (Chapter 7 of big pdf), US forests currently absorb about 13% of US carbon emissions. The distribution of this sink (in tonnes of carbon/hectare/year) is as shown above. Clearly the hilly regions of the eastern half of the country are critical, with the Pacific northwest being the second most important region.
The authors project that US forests will become a net source of carbon by mid century due to increases in drought, disease, etc, more than offsetting the benefits of a longer growing season and carbon fertilization.
This may be true - however, I imagine we will also create increasingly large financial incentives to manage forests for carbon storage and this may result in more intensive management of a lot of forests with species explicitly selected for that purpose, and for the changing climate. So I'm not sure this is beyond our control. Forests in the western US are at greatest risk - there is already a lot of wildfire and increasing insect outbreaks there and much more of the west is likely to desertify under climate change.