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Climate Change Predicted to Drive Trees NorthwardDecember 3, 2007
The most extensive and detailed study to date of North American tree species concludes that expected climate change this century could shift the trees’ climatic ranges northward by hundreds of kilometers and shrink the ranges by more than half. The study, by Daniel W. McKenney of the Canadian Forest Service and his colleagues, is reported in the December issue of BioScience. McKenney and colleagues’ study is based on continent-wide, georeferenced observations of 130 tree species in the United States and Canada, which allows better quantification of climatic tolerances than can be obtained from published range maps alone. The observation data--obtained from the US Forest Service and the Ministries of Natural Resources in each Canadian province, among other sources--were used to define the “climate envelope” of each species. If the trees were assumed to respond to climate change by dispersing their progeny to more favorable locations--the “full-dispersal scenario”--the ranges of the studied species would, on average, move northward by some 700 kilometers and contract by 12 percent, with some climate envelopes increasing in size and others decreasing. If the species were assumed to be unable to disperse--the “no-dispersal scenario”--the average expected range shift was 320 kilometers, and “drastic” range reductions of 58 percent were projected. The authors believe that most of the 130 species will fall somewhere between these two extremes of ability to disperse. The climate measures studied were chosen to represent important gradients for plants: heat and moisture. Two climate change scenarios were employed. One assumed that levels of atmospheric carbon dioxide would start to decrease during the coming century, the other that they would continue to increase. Each scenario was investigated with three well-known climate-change models, with broadly similar results. The authors note that although the general trend under climate change would be toward greater species richness in northern areas, the climate in southern areas would not be within the known climatic tolerances of the species they studied. They also note that their study investigated only a sample of the 700 or so tree species in North America, and that under climate change, new species might colonize the southern part of the continent from tropical regions. A companion article by the same authors applies the climate envelope approach to one species, the sugar maple. The complete list of research articles in the December 2007 issue of BioScience is as follows: Beyond Traditional Hardiness Zones: Using Climate Envelopes to Map Plant Range Limits Potential Impacts of Climate Change on the Distribution of North American Trees The Role of Animal-derived Remedies as Complementary Medicine in Brazil The Beginning of a New Invasive Plant: A History of the Ornamental Callery Pear in the United States Evaluating Existing and Emerging Connections among Interdisciplinary Researchers Biodiversity Studies and Their Foundation in Taxonomic Scholarship ContactJennifer Williams
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