Minnesota forests changing with climate: Forest Service study predicts winners and losers among tree species
That’s the finding of a major new study headed by the U.S. Forest Service Northern Research Station and released Thursday.
The study took an in-depth look at some 23.5 million acres of forest across northern Minnesota and describes both the effects of climate change that have already been observed as well as projections on what continued warming is expected to do.
The findings, which echo what many scientists already have said, are that trees already at the southern end of their range will do poorly — including balsam fir, aspen, white spruce and tamarack.
Tree species at the northern edge of their range will do better — including basswood, black cherry, white pine, red maple, sugar maple and white oak.
According to the report’s findings, significant changes in Minnesota’s climate have been documented over the past century. On average, northern Minnesota forests are seeing less snowfall but more severe winter storms. Meanwhile, minimum and maximum temperatures have been increasing across all seasons, with winter temperatures rising the most. Rainfall in the spring and fall has increased, with more of that precipitation occurring in downpours of 3 inches or more.
Mark White, a Duluth-based forest scientist with the Nature Conservancy involved in the report, said evidence suggests the climate is changing much faster than ever before and that tree species on their own can’t migrate or adapt fast enough to catch up.
The Nature Conservancy for the past two summers has been planting 2,000 acres in northeast Minnesota with red oak, bur oak and white pine seedlings — native species known to better handle warmer temperatures. In addition to planting warmer species, the group also is measuring if southern seed sources do better than northern seed sources for the same species.
“We’ve started thinking about the things we’re pretty sure will happen with a warming climate, about species that are going to fade and others that are more tolerant. So let’s increase the diversity of those species that are better suited to handling the stresses we think are coming up,’’ White said.
The report’s authors say the findings can help forest managers plot the state’s forest of the future rather than let chance rule the transition.
“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 Rains, director of the Forest Service’s Northern Research Station and the Forest Products Laboratory, in a statement.
The 240-page report predicts:
• Temperature increases will lead to longer growing seasons in northern Minnesota forests.
• The number of heavy precipitation events will continue to increase in northern Minnesota, and impacts from flooding and soil erosion may also become more damaging.
• Forests may experience more drought stress during the growing season, as well as increased risk of forest fires and an increase in forest pests and invasive species.
The forest assessment was developed with the contributions of more than 40 co-authors from organizations including the Chippewa and Superior National Forests, Minnesota Department of Natural Resources, University of Minnesota, conservation organizations, tribes, private industrial landowners and others.
“It’s a pretty detailed look ahead at what’s happening, with input from not just the academic people but also the hands-on forest managers,’’ White said. “It’s important to note that we aren’t certain on all of this stuff so we need to hedge our bets, like an investment strategy, and not put all our eggs in one basket. We’re trying to encourage diversity of species into the future.”