That could be bad news for lodgepole pine forests in southern Oregon, which have been devastated by bark beetle infestations and now may have a tough time making a comeback. Douglas fir and ponderosa pine, which are more adaptable, may move into the pine's territory.
The study predicts "large scale disturbances" in Pacific Northwest forests as temperatures rise 5 to 9 degrees by 2080, with more rain in winter and spring, reduced snowpacks and dryer summers.
Lead researcher Richard Waring, professor emeritus at Oregon State University, said forests of the future will look much different. As the climate changes, tree species that have been established for centuries will lose their competitive edge and either decline or disappear, he said.
"Some of these changes are already happening, pretty fast and in some huge areas," Waring said in an OSU news release.
The study says some forested areas may transform over time into grass savanna or sagebrush desert. In central California, researchers said more than half the tree species aren't expected to survive. Western Oregon and Washington, where growing conditions are wet and mild, will see less species change than the more extreme forest zones.
The biggest change may occur to the north, in inland British Columbia and Alberta, according to the study. In those areas, the frost-free period is expected to increase by at least a month and periods of extremely warm summer days are likely to become more common.
With less snow cover and spring frost, trees begin their growing season earlier. But those conditions also favor insects and diseases that can kill tree stands, the study says. Douglas fir, grand fir and western hemlock, which favor more temperate conditions, may establish themselves.
The research was done with remote sensors in 34 eco-regions in western Canada and the United States, ranging from the Columbia Plateau to the Sierra Nevada mountain range, and including the Snake River plain and the Yukon Highlands. Fifteen coniferous tree species were studied over a four-year period.
Studies on "range shift" due to climate change have been in the news for several years.
A 2008 study predicted that up to two-thirds of the 2,400 plants that grow only in California will undergo range reductions of greater than 80 percent within a century. The state's varied terrain might make it difficult for plant species to migrate to more favorable growing areas, researchers said. Protecting such "refuge" areas and aiding species dispersal is essential to "maintain bio-diversity in the face of climate change," the study concluded.