Dramatic Shift in Treeline Predicted

By Randy Boswell
Bali (December 4, 2007)- On the eve of a key international climate change conference in Bali, a major Canadian-led scientific study is predicting dramatic shifts in North America’s tree cover this century –including widespread losses of species in drier parts of the United States, but a much richer diversity of trees in southern Canada and a northward march of forests that could see stands of sugar maples sprouting along the James Bay shoreline.


“It’s really an unprecedented habitat shift,” said Canadian Forest Service landscape analyst Daniel McKenney, lead author of a paper published with three other federal government researchers and an Australian scientist in the latest edition of the journal BioScience.
“There will be parts of the country that will have more tree species than they currently do,” said Mr. McKenney, describing how warming temperatures would essentially redraw Canada’s vegetation map so that “sugar maples and other hardwoods could be grown around Hudson Bay.”
But the study, considered the most comprehensive of its kind, also predicts “unprecedented pressure on ecosystems” north and south of the U.S.-Canada border, as dry regions- including the Canadian Prairies- struggle to maintain existing species and the expansion of other trees’ growing ranges affects wildlife distribution, harvesting practices and a host of other biological systems.
Mr. McKenney said changing climate is only one variable affecting the distribution of trees, and that soil conditions, inter-species competition, and other factors make precise predictions difficult.
It’s also not clear how quickly or effectively certain species will migrate even if the expected changes in temperature and moisture levels would theoretically support expansions of their ranges. But one scenario constructed by the research team showed a “remarkable” average northward shift in growing ranges of 700 kilometres, said Mr. McKenney.
“Alaska, the northern Prairie provinces, Ontario, Quebec and the Maritimes are predicted to experience future climate that is favorable for a wide variety of tree species,” the authors state. “Conversely, by the end of the century, the climate in much of the southern United States will not be within the current known climatic tolerances for most of the 130 species in this study.”
Mr. McKenney said scientific bodies and government resource managers are already debating “how we move things around” pending widespread climate change. For example, he said, experts are grappling with ethical issues such as whether to begin planting economically lucrative trees — including sugar maples — beyond their current “maternal climate” in anticipation of expanded growing ranges.
About 190 nations are in Bali seeking a breakthrough for a new global pact to include the United States and developing countries to fight climate change.
For the full article, visit the National Post.