Aleta McKeage speaks about a shagbark hickory tree last month as she leads a tour of the City Park Arboretum in Belfast. Scientists are trying to find species that can survive in Maine as temperatures warm. Shawn Patrick Ouellette/Staff Photographer

BELFAST — Aleta McKeage wanders the shady groves and manicured meadows of City Park arboretum like a data-driven grim reaper, pointing out one iconic Maine tree after another that climate scientists predict will decline or disappear over the next 75 years.

Red spruce, balsam fir and paper birch. Beech, elm and ash. These are some of the native species likely to see their numbers cut in half, or worse, by the end of the century, either because of climate change or the pests and diseases that will thrive in it, said McKeage, a conservation biologist and technical director at the Waldo County Soil and Water Conservation District.

Aleta McKeage holds a branch from a black walnut tree while she leads a tour of City Park Arboretum in Belfast. It is one species that may thrive in Maine and provide wildlife forage and other benefits that may be lost when other species dwindle because of rising temperatures. Shawn Patrick Ouellette/Staff Photographer

“The trees are both our witnesses and our prophets, showing us the consequences of what we have done to our ecosystem,” she said. “They are dying because we are hooked on fossil fuels. They are tangible proof of climate change.”

McKeage mourns the pending loss, but she is already trying to ensure that Maine’s forests do not give way to wastelands of invasive, shrubby buckthorn or honeysuckle. She plans to fill any holes in Maine’s future ecosystem with trees that can thrive in a warmer climate.

It is called assisted forest migration, the relocation by humans of a tree species from its current habitat to a new one. Such a move could be small, from one part of a species’ natural range to another, or it could be big, moving a species someplace well outside of its traditional natural range and hardiness zone.

These new heat-tolerant trees need to fill jobs that climate change could leave empty. To replace the beech, a new tree should produce rich nuts for wildlife. A red spruce replacement should produce good lumber. To replace the hemlock, a new tree must protect the water quality of forest rivers and streams.


McKeage walks a tour group past a string of likely candidates planted around the arboretum: shagbark hickory, tulip poplar, black walnut, sassafras, and white, scarlet and bur oaks. Other possible choices are waiting in the wings, including pawpaws, redbuds and spicewoods.

The shagbark is a favorite. McKeage gushes over the hickory’s namesake peeling bark, which can create snug crevices where bats can roost, and its wood, a favorite for making floors and for smoking meat and fish. Shagbarks already grow in Maine – Viles Arboretum in Augusta is home to one that is 40 feet tall.

McKeage is also fond of the poplar, whose tulip-shaped flowers make a sweet, mineral-rich honey that attracts pollinators. Its small seeds, which linger into the winter, feed birds, squirrels and rabbits. It’s also a valuable source of lumber, veneer and pulpwood.

The tulip poplar isn’t native to Maine, but it’s moving north and has grown everywhere she’s planted it.


“How do we know these won’t become invasive?” a member of the tour asked McKeage. “What if it’s the trees you are planting to save the forest that wind up changing it? It feels like you’re playing God. It feels dangerous.”


McKeage is used to this question. As a conservation biologist, she agrees that nature usually knows best. But the challenge facing Maine forests isn’t natural, she said. Humans created climate change. Now they have to clean up the mess and help forests adapt to what’s coming.

Curbing fossil fuel use and reducing greenhouse gas emissions that trap sunlight in the atmosphere and cause temperatures to rise is the only way to slow global warming, she explains. If we do that, we would give southern trees adapted to a warmer climate time to naturally migrate northward.

Through natural seed dispersal, forests can travel about a tenth of a mile every year. But the wind, water and animals that help them on their way cannot carry the seeds far enough to keep up with today’s rapidly warming climate, which is shifting 4 to 6 miles north each year.

That gap has severe implications for Maine, the most heavily forested state in the nation, McKeage said. Our forests are not only essential to wildlife and water quality, they absorb 60% of our carbon emissions and support an industry that employs 33,000 people and pumps $8.5 billion into the state economy.

“You may not see it because trees grow slowly, but our forests are fighting for their lives,” she said. “Yes, there are questions of overaggressiveness, how they will naturalize – but our research will figure that out. We need to start planting these trees now, or we’re going to have a barren landscape within decades.”



The doom-and-gloom forecast for Maine’s forests is built on climate-based population modeling, which factors in a species’ ability to adapt to heat, summer drought and seasonal rainstorms, the availability of suitable habitat, and differing levels of future greenhouse gas emissions.

Depending on future greenhouse gas emissions, Maine’s mean annual climate could warm by up to 4 degrees Fahrenheit by 2050 and up to 10 F by 2100. Maine also is likely to see more frequently occurring and more intense rain in the spring and fall, and more frequent and intense summer droughts.

Warmer temperatures and more carbon dioxide in the atmosphere could actually boost the productivity of Maine’s forests but will likely change the species that thrive in them. Predicting which will decline and which will thrive is an emerging science, playing out in fields and forests across the country.

Whether a species will make it depends both on the amount of suitable habitat that will be available and the ability of the species to adapt. Some of Maine’s current tree species might be able to adapt to hotter climates and summer droughts better than predicted.

But assessing their futures is complicated. For example, trees lose water through the same pores they use to absorb carbon dioxide. In the future, in a carbon-loaded atmosphere, trees may be able to shrink these pores, reduce the amount of water escaping their leaves and still get enough carbon for photosynthesis.

Managers of Maine’s public lands are tracking the turnover of tree species to gauge the rate of change and to vet the veracity of the climate modeling. Some are taking a wait-and-see approach, some are planting warm-weather test trees only to rip them out, and others say they are planting for keeps.


At Acadia National Park, said Superintendent Kevin Schneider, park managers are doing experimental planting to see which trees might be best suited to Mount Desert Island’s future temperatures, which are projected to rise between 5 and 13 degrees by the end of the century.

Seven of the park’s 10 most common tree species, including such iconic ones as the red spruce, paper birch and balsam fir, are expected to decline or possibly even disappear by 2100, forever changing the look of Acadia’s tree-lined mountains and rocky shores, Schneider said in a recent talk at UMaine.

“The most important long-term challenge we’re facing is climate change,” he said. “Rewind five or 10 years, I would’ve said climate change was something that would happen in the future, maybe after retirement. Well, I was wrong. Climate change is something we are seeing now.”

A basswood tree at City Park Arboretum in Belfast on Sept. 8. Shawn Patrick Ouellette/Staff Photographer

The number of red spruce, one of Maine’s most common and valuable trees, is likely to decline by 50% by 2100, according to the U.S. Forest Service’s climate change tree atlas, a modeling tool developed to map current and projected suitable habitat for 134 tree species in the Eastern United States.

But right now, to anyone walking through one of Maine’s trademark balsam-fir forests, the red spruce appears to be a very happy tree. It is making a comeback after acid rain setbacks now, benefiting from tighter pollution controls, but its gains aren’t expected to last past 2050.

“If the red spruce declines, the coast of Maine is going to look a lot different,” Schneider said.


It is now Acadia’s most common tree, accounting for 39% of all of the park’s forests. It provides winter cover for American marten and white-tailed deer, and it feeds the grouse, snowshoe hare and the white-winged crossbill, whose odd bills are perfectly adapted for prying open spruce cones to get at the seeds.

By 2100, about half of the red spruce habitat in the park is projected to change into something more suited to warm-weather species of trees, forcing wildlife that likes to nest in the red spruce and nibble on them to compete for the red spruce that remain or move to a less-suitable tree.

The red spruce decline is expected to drive the white-winged crossbill out of Acadia by 2150, according to Maine Audubon. It is one of 60 bird species, scientists say, that Acadia likely will lose as the iconic spruce-fir forest gives way to heat-tolerant hickories and oaks or worse, shrublands.

Acadia has adapted a “resist, accept or direct” approach to addressing climate change in the park, Schneider said. It will resist change to protect what people love most, like Thunder Hole, for example – as long as sea-level rise, surges from more frequent storms and park budgets allow.

But at some point, spending millions of dollars to repair Thunder Hole every time the ocean reshapes it – especially when sea-level rise and increasing storms are accelerating the need – becomes a “fool’s errand,” Schneider said. That is when a superintendent must accept change and walk away.

When it comes to Acadia’s forests, Schneider said, the park is experimenting with directing change. The park has done several adaptive plantings to see which tree species can survive the winter now and thrive in the climate conditions likely to exist in the future.


The plantings were mostly experiments in adapted population migration, bringing in southern versions of species that already grow in the park with the hope of benefiting from any warm-weather adaptations that the southern varieties might have developed, Schneider said.

Seedlings from 16 mid-Atlantic species were planted in four raised beds built around the park in 2018. Tulip poplar thrived at every site, growing fast in differing sunlight and elevations despite two summer droughts. The sweet gum failed at all sites, its star-shaped leaves turned brown by the harsh winters.

But all the park’s experimental trees were eventually ripped out, the leaves and stalks sacrificed for science and Acadia kept in its natural state.

The red spruce may not disappear entirely. According to Nick Fisichelli, president of the Schoodic Institute, the park’s nonprofit research arm, some models suggest the cool, moist summers and abundance of shaded slopes could make Acadia a safe haven, or a refugium, for the species.

“All of this is very young research,” Fisichelli said. “The challenge with trees, of course, is that they’re not annual crops. They grow for decades. It is challenging to follow the science because it does take time – but given how fast climate change is happening, we may not have that kind of time.”

Schoodic is also involved in a longer-term assisted forest migration study following the growth of 1,500 saplings from 10 warm-weather species planted two years ago on land trust or private properties in Bar Harbor, Belfast, Blue Hill, and on the Schoodic peninsula.


Acadia’s interest in assisted migration started in 2014 after Fisichelli, then working at the National Park Service’s climate change center in Colorado, applied the species predictions generated by the U.S. Forest Service’s Climate Change Tree Atlas to East Coast parks, including Acadia.

The U.S. Forest Service is doing some experimental planting, but the focus is on commercial species. It is also working with university research centers and private timber companies to improve the genetics of commercial species to make them heat- and drought-tolerant and resistant to blight and pests.

Maine’s largest private forest owner, Irving, did not respond to requests for interviews.

Aleta McKeage talks about a grove of basswood trees, a species normally found in more southerly areas, while leading a tour of City Park Arboretum in Belfast. Shawn Patrick Ouellette/Staff Photographer


Experiments like the one at City Park arboretum and Acadia are happening around the state, led by private land trusts, environmental organizations, religious orders, colleges and private forest owners. McKeage is teaching people how to do them at the Common Ground Education Center in Unity.

Last year, under her guidance, the Maine Organic Farmers and Gardeners Association planted a circular plot of 14 warm-weather trees in a grove at the edge of a young forest near their farming headquarters, with two or three trees of different sizes from six different species.


A smaller second planting on the 1-acre plot followed this spring.

“There is hardcore research going on, yes, but there is also a great need for community science, for us to find out what works as soon as possible, in as many different settings as possible,” McKeage said during a recent rain-soaked tour of the MOFGA demonstration site.

She pointed out the black walnut to the land trust steward trailing along behind her, noting its beautiful dark wood and its sweet-smelling nuts. “Most Maine forests are privately owned,” McKeage said, waving her arms at her dozen pupils. “We need to reach these people.”

The tests are not without their limitations. Just because a tree can be planted and survive in Maine does not mean it could become naturalized, able to survive without being watered or protected from deer and rabbits and capable of producing the nuts and seeds necessary to create the next generation.

Even if someone had the time and money to plant adapted species in the gaps of a family-owned forest, finding enough saplings adapted to our projected climate could prove to be a challenge, especially when Western states are vying for saplings to replant after wildfires, said Maine State Forester Patty Cormier.

Because Maine foresters generally rely on forests, even commercial ones, to self-seed, the state closed its only tree nursery in 1988. New Hampshire is the sole New England state that still operates one. That may soon change, however. Cormier is applying for a federal grant to reopen the state-run tree nursery.


According to Tony D’Amato, the director of the University of Vermont’s forestry program, New England is behind the curve. The West is continually replanting after wildfires, so planning for the future makes sense. Joshua Tree National Park is considering a more radical plan: relocate its namesake tree north.

Meanwhile, New England states like Maine are only now getting used to the idea of planting forests at all, he said. Planting a resilient forest in New England will not be easy, or cheap, especially compared to the the usual self-regeneration approach to forest management, he said.

“To do this, you’re not going to be planting just one northern red oak, but more like 100,” D’Amato said. “And in 50 years, if one of those 100 survives to become a sexually mature tree producing acorns, that’s success. Add a self-regenerating hickory and a poplar, and then that forest has a shot.”

Letting go of what we have always known can be hard, D’Amato acknowledges. He is the first to admit he will have a hard time, and probably shed more than a few tears, if the day ever comes when sugar maples disappear from the hardwood forests of Vermont.

D’Amato understands that Mainers probably feel the same way about the red spruce and the paper birch.

“It’s going to be hard trying to figure out what to save and what to let go,” D’Amato said. “Sometimes, we won’t be able to save something we love. That’s when we have to remember what’s important: the carbon fixing, the wildlife food, the clean water, the jobs. Don’t lose sight of the forest for the trees.”

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