Planting a forest for a warmer Northland

·5 min read

Jun. 11—Scientists are worried that several species of trees in Northland forests may not be able to adapt fast enough to the region's rapidly warming climate.

Trees that favor cooler temperatures are retreating north, they note, and it's not clear yet which species will move up from the south to take their place.

Already, some of the Northland's signature tree species — paper birch, balsam fir and white spruce — are giving way to invasive grasses and shrubs in some areas. And if grasses and shrubs are the warmer future for Northland forests, what does that mean for the tourism and wood-products industries and for the wildlife that thrive here now?

But not everyone is sitting around waiting to find out what happens decades down the line. Multiple efforts are underway to get a jump-start on so-called forest migration by planting trees most likely to thrive in our warmer world.

It's called "assisted migration."

Across four North Shore state parks this summer, the Nature Conservancy has planted 100,000 warmer climate-adapted native trees, helping replace the region's dying crop of birch trees that have been withering for decades. The new plantings include white pine, red oak, bur oak, yellow birch, white cedar and tamarack — all species known to do well in warmer conditions but which are native to Minnesota.

North Shore forests have changed dramatically over the last century. Once dominated by pine, fir, spruce and cedar, clear-cut logging a century ago took most of the big seed trees. Those that weren't cut were hit by slash-pile fires that burned much hotter than previous wildfires in the area. What grew up after that was a lot of paper birch and invasive grasses.

Now, most of the birch have reached the end of their normal life span. But those grasses have blocked the way for new trees to replace the birch. Add in the northern migration of deer into the area over the last 100 years and species like white pine that do sprout never get the chance to get big — the whitetails eat them as fast as they can.

The Nature Conservancy seedlings were planted in Split Rock, Temperance River, Cascade and Gooseberry Falls state parks. Park visitors may see fencing and protective enclosures around new plantings to protect them from deer. As the trees grow, visitors will be able to see how the forest changes over time and how different species of wildlife are attracted to it.

— Duluth's winters warmer, snowier than a decade ago

— Study: Minnesota, Wisconsin could plant millions of acres of trees to soak up carbon dioxide

— In warmer Minnesota forests, drier trees will grow slower

— North Shore forest restoration expands tree by tree

— Amid vast tracts of dying birch trees, residents planting the seed to restore Minnesota forests

The Nature Conservancy is doing the work with an anonymous family grant and help from the Minnesota Department of Natural Resources, the U.S. Forest Service, the Grand Portage Band of Lake Superior Chippewa and the North Shore Forest Collaborative.

"State parks are not only a great place to get outdoors, but they are also home to vast natural resources that need protection and active management to remain healthy into the future," Liza McCarthy, district resource specialist for the DNR, said in a statement. "These forests have changed from what was once here due to turn-of-the-century logging practices, deer ... and climate change."

Forestry experts say forests with more diverse mixes of species and ages of trees are more resistant to insect and disease threats and host a broader variety of wildlife species. Big trees on the landscape help slow rainwater runoff and erosion, shade streams to keep water cool for trout and capture and store carbon to help slow climate change.

Christopher Anderson, regional director for The Nature Conservancy, said the organization to date has planted 5.5 million trees on about 18,000 acres across Minnesota's northwoods.

Of course it's not just trees that are moving north. Studies have shown that some animal species are moving an average of 11 miles north, or 36 feet higher in elevation, each decade to find more hospitable places to live as the climate changes. In Minnesota, species like moose, lynx, lake trout, brook trout, northern flying squirrels and likely spruce grouse all face diminished territory as the climate warms, pushing them north into Canada.

UMD developing warmer-weather seeds for nurseries

Meanwhile, at the University of Minnesota Duluth, researchers and students are testing and growing seedlings that are expected to do well in the region.

It's called the Forest Assisted Migration Project, a grant-funded, five-year effort to build a regional market for cultivating climate-adapted tree seedlings from local farms and nurseries to provide the future stock to replant Northland forests.

Without help from more farmers, however, there won't be enough seedlings to replant forests fast enough to keep up with climate change. Current annual seedling production in Minnesota is roughly 6.1 million across both public and private nurseries, but one study found tens of millions of trees will be needed.

Advocates are calling for more and better seed collection in addition to nursery production and adding more field crews to plant trees and protect them from deer and invasive species.

"The five-year goal began with detailed research in order to find the right trees to grow in our warming climate," says Julie Etterson, head of UMD's Biology Department.

The first batch of UMD seedlings has been planted and cared for by farmers and will soon be large enough to plant in the forests of Northeastern Minnesota, and the Nature Conservancy has agreed to buy 40,000.