Boreal forest carbon stocks and wood supply: Past, present and future responses to changing climate, agriculture and species availability

The paper assesses the role in boreal forest growth played by environment. It examines past changes in climate coupled with glaciation, and future changes in climate coupled with agricultural land use and tree species availability. The objective was to define and evaluate potential future changes in wood supply and global carbon stocks. Calculations were based on a standard static vegetation model (BIOME 1.1) driven by the most recent climate change scenarios from three coupled ocean-atmosphere general circulation models (GCMs). The results indicated that boreal terrestrial carbon stocks increased greatly following the retreat of continental ice sheets, before which boreal forests covered only about a third the amount of land they cover now. Carbon stocks and wood supplies in boreal forests were also projected to increase if vegetation stabilized under all three future climate scenarios (6-15%). However, the opposite response occurred with the addition of expected constraints on forest growth, provided by the lags in immigration of tree species suitable for warmed climate. This transient depauperate condition reduced wood supplies considerably (4-6%). Inclusion of present and future agricultural land uses permitted by a warming climate forced carbon stocks and wood supplies to decline even more (10-20%). The decline in boreal carbon stocks is the equivalent of 1-2.6 Pg year(-1) emitted to the atmosphere (rather than the 1-2 Pg year(-1) global modelers hypothesize is currently being taken up by vegetation from the atmosphere), during the time greenhouse gases are expected to double in concentration.