Over the next 100 years, Minnesota's iconic boreal forest and deep snow may change into a deciduous forest with winters warm enough for some precipitation to fall as rain, according to a new U.S. Forest Service assessment of the vulnerability of Minnesota forests to climate change.

The assessment describes effects of climate change that have already been observed; projected changes in the climate and the landscape; and forest vulnerabilities in a 23.5-million-acre region of forest in northeastern Minnesota.

Tree species that are already at the southern end of their range, such as balsam fir, quaking aspen, white spruce, and tamarack, are expected to decline over the next century while American basswood, black cherry, eastern white pine, red maple, sugar maple, and white oak may gain suitable habitat across the landscape.

"By planning ahead, foresters and other decision-makers can begin now to manage for resilient landscapes and ensure that the benefits that forests provide are sustained into the future," said Michael T. Rains, Director of the Northern Research Station and the Forest Products Laboratory. "Forest Service science is delivering information and new technology that will help managers in Minnesota and throughout the nation meet this challenge."

Changes in Minnesota's climate have been documented over the past century. In general, the state is experiencing less snowfall in the area covered by the assessment, but more severe winter storms. Mean, minimum, and maximum temperatures have been increasing across all seasons, with winter temperatures experiencing the most rapid warming. Precipitation in the spring and fall has increased, with more of that precipitation occurring in deluges of 3 inches or more.

What might these changes mean for forests?
+ The projected temperature increases will lead to longer growing seasons in the assessment area.

+ The number of heavy precipitation events will continue to increase in the assessment area, and impacts from flooding and soil erosion may also become more damaging.

+ Forests may experience more drought stress during the growing season.

+ Climate conditions will increase fire risks by the end of the century.

+ Many invasive species, insect pests, and pathogens could increase or become more damaging.

"There are so many variables that will affect the future of forests in northern Minnesota, forest managers will probably always have to deal with some amount of uncertainty," said Stephen Handler, lead author of the vulnerability assessment and a climate change specialist with the Northern Institute for Applied Climate Science (NIACS).

"But we already know enough right now to begin planning for a range of possible futures. Our assessment gives forest managers in Minnesota the best possible science on the effects of climate change, so they can make climate-informed decisions about management today."

More than 30 scientists and forest managers contributed to the assessment, which is was conducted as part of the Northwoods Climate Change Response Framework, a collaboration of federal, state, academic, and private partners led by the NIACS.

NIACS is a collaboration of the Forest Service, Michigan Technological University, The Trust for Public Land, and the National Council for Air and Stream Improvement. The Climate Change Response Framework and this assessment are local examples of information provided by the new USDA Climate Hubs and the Forestry Sub-Hub located in Houghton, Mich.

"Minnesota Forest Ecosystem Vulnerability Assessment and Synthesis" was published by the U.S. Forest Service's Northern Research Station.