Climate change and shifts in potential tree species range limits in the Great Lakes region

The model STASH (STAtic SHell) was used to generate current and future potential geographic ranges of ten important forest tree species within the Great Lakes region. This model uses bioclimatic variables to predict the suitable climate-space for tree species. Current climate values were derived from weather records, and two general circulation models (CGCM1 and HadCM2) predicted future climate scenarios. Shifts in potential ranges that were predicted by the two climate models were similar in direction, but different in magnitude. Important timber trees with southern limits within the Great Lakes region, including white, jack, and red pine, aspen, and yellow birch are predicted to retreat northward under both scenarios due to increasing summer temperatures. Under CGCM1, these trees are predicted to disappear from most of the region by the end of the century, whereas under HadCM2 they are predicted to contract 100 to 200 km from their southern range limits. A number of broadleaf trees (red oak, sugar maple, and beech) are expected to remain in the region and may gain potential habitat to the west. Broadleaf trees with current northern range limits within the Great Lakes region (black walnut and black cherry) are predicted to gain potential habitat to the north due to increases in growing degree-days and coldest month temperatures. Both trees are predicted to be able to grow throughout the region by the end of the century under CGCM1, and a less dramatic gain is predicted under HadCM2.