We know from fossil pollen records that ever since there have been trees, they have moved independently from one another all over the continent. They have moved according to where there was both a comfortable climate and a suitable habitat. As climate changed, trees adapted and changed locations.
Predicting future climates and the movement of trees is no small task. But recently the National Park Service (NPS) Climate Change Response Program made it easier for Grand Portage National Monument and the forests of 121 other national park units. Utilizing models developed by the U.S. Forest Service and provided to the public in a Climate Change Tree Atlas (www.fs.fed.us/nrs/atlas/), the NPS summarized the future potential movements of tree species’ preferred climate from 1990 to 2100. While these climatological envelopes (as they are called) are important, they should not be interpreted as actual tree habitat movements.
Climatological envelopes do not account for major forest stressors such as emerald ash borer, soil diversity like deep North Shore clay, bedrock or beaches, topographically complex microclimates, lake effects or the landscape connectivity needed to facilitate the migration of an eastern species to our northern forests.
Forest managers will have to account for all these factors when they consider potential movements of tree species. For example, it may be very hard for the acorns of white oak trees to drive their migration to newly suitable habitat on the North Shore unless forest managers plant them. As trees’ preferred climate continues to move across the continent, there will be new arrivals to this area, decreases in some present species and yet increases in some others. Some of the more significant findings:
. Possible total loss or probable very heavy losses by
2100: Mountain maple, black spruce, pin cherry
. Probable large decreases by 2100: White spruce
. Probable large increases by 2100: Northern red oak
. Possible new migrants and probable large increases by 2100: Black cherry, white ash, black oak
. Possible new migrants by 2100: Sweet birch, white oak, bur oak
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