Pennsylvania's forests will be affected by a changing climate during this century.
Pennsylvania's forests will be affected by a changing climate 
during this century. These handouts summarize projected changes in tree species habitat for four regions in Pennsylvania and provide the complete model results for those regions.
Please note: The Lake Erie and Ontario Lake Plain (Region 2) and Atlantic Coastal Plain (Region 6) are too small for analysis; data for these areas are best combined with the broader Mid-Atlantic region.
Climate Change Tree Atlas
Two climate scenarios were used to “bracket” a range of possible futures. These future climate projections were used with the USDA Forest Service Climate Change Tree Atlas to provide information about how individual tree species' habitat may change. More information on the Tree Atlas can be found at www.fs.fed.us/nrs/atlas. Results for “low” and “high” climate scenarios can be compared in each summary for the following subregions:
3 - Northern Allegheny Plateau
Heat and Hardiness Zones
Some trees were not modeled by Tree Atlas. For these species, climate change effects can be assessed by examining future projections of hardiness zones and heat zones for regions of Pennsylvania (right). The climate change effect was calculated by comparing the species’ published heat zone tolerance to the map of projected heat zones under two climate scenarios. As temperatures increase, it is expected that hardiness and heat zones will shift by up to 3 hardiness zones and 5 heat zones by the end of the century.
This handout provides more information on heat and hardiness zones
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Remember that models are just tools, and they’re not perfect. Model projections do not account for some factors that could be modified by climate change, like droughts, wildfire activity, and invasive species. If a species is rare or confined to a small area, Tree Atlas results may be less reliable. These factors, and others, could cause a particular species to perform better or worse than a model projects. Human choices will also continue to influence forest distribution, especially for tree species that are projected to increase. Planting programs may assist the movement of future-adapted species, but this will depend on management decisions.
Despite these limits, models provide useful information about future expectations. It’s perhaps best to think of these projections as indicators of possibility and potential change. The model results presented here provide the best information when combined with information from published reports and local management expertise.