Adapting to an uncertain climate future, Connecticut auditions new forests
At 9:30 on a morning in late May, it was already hot and promising to get hotter as a dozen or so volunteers gathered at the Hoffman Evergreen Preserve in Stonington. They were there to plant trees – a seemingly curious activity, considering the preserve is already a forest.
But planting those trees – a mere 150 or so on this particular day – is intended to do more than just revitalize the woodland. Along with a few similar projects around the state, the Hoffman work may help set a course for how Connecticut can adapt its forests to withstand the effects of climate change.The nearly 200-acre preserve, which was mostly hemlocks and other evergreens, is aging, overgrown and so crowded nothing grows beneath the trees, known as the understory. Some tree species, including hemlocks, ash and others, have been all but decimated by pests that are now able to survive year-round due to Connecticut’s warming winters.
“All these tragedies, a lot of them do seem to be exacerbated by warmer winters,” said Beth Sullivan, a volunteer with the Avalonia Land Conservancy, which has owned the preserve for more than four decades. She is Avalonia’s point-person on the project, along with Juliana Barrett from the University of Connecticut.
Both are giving orders this morning on what goes where and how.
“It’s gonna start getting hot, so I don’t expect huge efforts, but if we could come out here and do some watering, for instance. This is my priority for the summer — getting this place watered. And watch out for the invasives and things like that,” Sullivan tells the volunteers.
Working with foresters, Audubon Connecticut, the state and other experts, Avalonia Land Conservancy made the decision to clear five areas — called patch cuts — to get rid of dead and dying trees, sell the good ones as lumber (which more than covered the cost of the work) and allow in light and water for the first time in decades.
But then what?
“The idea came from a few of us brainstorming,” said Sullivan, who felt there was an opportunity to do something other than just let nature and climate change take over.
“Maybe we could think about a resilient forest,” Barrett said. “What’s going to do well here in future?”
Three patch cuts are now demonstration projects with a total of nearly 600 new trees and shrubs, including this day’s 150. Nearly all were planted about a year-and-a-half after the patch cuts were completed, work that was delayed by the pandemic. One of the three cuts is a control area to see what comes in on its own.
The point of the other two is to address the problems assailing Connecticut forests by adapting to the changes wrought by climate change while simultaneously embracing longstanding practices for creating resilient forests, something that had not been done in the Hoffman Preserve.
Broadly, that means planting trees that are used to the weather and climate conditions that are becoming increasingly common here while being mindful of the best way to cultivate trees under any conditions.
That often means planting trees that normally grow to the south of here. But it’s not that simple.
A layering of threats
The best place to start if you want to understand what is happening now and could happen in the future to New England’s trees is the upper peninsula of Michigan.
That’s where Maria Janowiak is based as acting director of the Northern Institute of Applied Climate Science at the U.S. Forest Service Northern Research Station, which is part of the USDA. From there, she coordinates the Climate Change Response Framework project in New England and Northern New York. Loosely translated, that means she helps all kinds of scientists, forestry professionals and regular folks figure out how to figure in climate change.
Pretty much everyone working seriously on tree preservation in Connecticut is consulting her.
Janowiak and her team have supplied the region with two bibles: a Vulnerability Assessment of the region’s forests, published in 2018, and a Climate Change Tree Atlas, which looks at how existing trees are likely to be affected by a changing climate.
“One of the major outcomes that is really clear is that there are a lot of stressors on the landscape now and legacies on the landscape now that are influencing the forest,” Janowiak said.
The standard stressors are things like past land use and land management — the constant push and pull between agriculture and the forest. There are invasive plant species, introduced pest species, deer and other animals, and the impacts from human behavior.
“Essentially climate change becomes an additional factor on top of that,” she said. “So in the near term, it’s really hard to tease out the influence of climate versus these other stressors, because they’re all interacting.”
That theme plays out over and over in the world of climate change prediction. With no real models to draw on, even one change in any ecosystem dynamic will ripple through, changing or not changing other elements of the ecosystem, which in turn change even more elements. Scientists like Janowiak don't engage in guesswork, but with so many shifting variables — some clearly due to climate change and some not — figuring out what the future holds for the region’s trees may seem next to impossible.
But that’s what the Climate Change Tree Atlas does. It looks at trees throughout the eastern United States, sorting them by state or smaller areas. Using records from several million trees and more than three dozen factors — including levels of emissions, temperatures, soil conditions, rainfall, you name it — it then makes predictions about the future of the region’s trees. How suitable is the habitat? What is the potential for migration in or out of that area? How adaptable is the species? What trees will be in Connecticut and where by the end of the century?
This is some of the information the Hoffman Preserve team and other researchers are using.
Among 92 trees the atlas ranks in Connecticut, the adaptability to climate change rating is less than promising for a number of currently abundant trees, such as sweet birch, Eastern white pine, Eastern hemlock and white ash. Hemlock and ash are already under massive stress from pests — hemlock wooly adelgid and emerald ash borer. Throw climate change on top of that, and all bets are off.
American beech, which is quite common in the state, is now facing infestation from a nematode that causes beech leaf disease. The Connecticut Agricultural Experiment Station recently declared the disease “widespread,” leaving it more vulnerable to stress from climate change.
The atlas shows that several trees are likely to be lost or be in very poor shape by the end of the century, including some pines, oaks and hickories, but none of the ones that are most abundant now.
About one-third of the trees in the atlas are trees that are uncommon in Connecticut but they are included because of their potential to spread here due to the changing climate.
There is often worry that, unlike birds, insects and other critters that can fly or at least easily move elsewhere as climate changes, trees have a much slower evolutionary and adaptation process. But Chris Martin, state forester and the director of the Department of Energy and Environmental Protection’s forestry division, said Connecticut has one advantage because it’s located in a transitional hardwood zone — with one leg in New England and the other in the mid-Atlantic. That means the range of tree species that can grow here might be large for a small state.
“As we lose trees to climate or insects, you throw sun on the area,” Martin said, adding that this lets other species in. “It’s a hard way to get there and you have a lot of death and destruction in the process, but you get to the same end.”
Janowiak points out that many tree species in Connecticut have ranges that extend farther south, which means they are already adapted to many of the anticipated climate changes. A lot of oak and pine species, for instance, can tolerate drier, warmer conditions.
“So the tree species and the forest types are generally not considered to be that vulnerable as assemblages,” she said. “But it’s the layering of these additional stressors onto them that creates a lot of the concern about forest conditions over the long term.”
The direct climate change stressors often wallop trees with polar opposites — extreme heat and extreme cold, drought and flooding. While pests are often cited by the scientific community as the primary threat to trees here, climate change conditions often make it easier for certain pests to thrive.
Pests plus climate
Among them are gypsy moths, which have decimated the region’s oak trees in recent years. The fungus that keeps the moths at bay needs substantial spring rain. In 2016, when that didn’t happen, the results were catastrophic, especially in eastern Connecticut.
In a year like 2021, which had a cold, wet spring followed by drought and heat, it wasn’t clear what would happen, but heavy rains followed and that may have salvaged the situation in eastern Connecticut. But it didn't help the western part of the state, where thousands of acres around Sharon, Cornwall and Kent are already defoliated due to gypsy moth infestation.
The southern pine beetle, causing damage on Connecticut’s southern doorstep right now, is scattered around the state but doesn’t have much of a grip here — yet. It likely will eventually be helped by the lack of cold winter temperatures that would otherwise kill them.
The presence of those pests and others also means that when more obvious climate conditions like severe tropical storms, heavy snow or winds hit, the already stressed trees are less likely to survive.
Climate changes can also pave the way for the spread of new invasive plant species, which, aside from taking over a landscape, often come with their own sets of pests and problems that can have impacts on whatever is already here. Birds that shift habitat due to climate change may no longer be around to eat the pests that now are alive to harm trees.
Forests in Connecticut and throughout New England have a few other region-specific problems. The trees tend to be fairly uniform in age — 100 to 120 years old — the product of a reforestation push early in the 20th century to recover from large scale tree removal in prior eras of farming and logging. They also tend to be uniform in species, which makes them more broadly susceptible to any given stressor. In other words, if one tree in a species goes, odds are good that others in that species will too.
Also uniform – what folks cite as the core step to start correcting what ails Connecticut forests.
“Diversity, diversity, diversity,” said Avalonia’s Sullivan even before the question was finished.
“Diversity is the hedge against the unknown because diversity provides you many paths to redirection or change,” said DEEP’s Martin.
“If you have a diversity of tree species out there, you’re not going to pick the winners or losers,” said Jeffrey Ward, chief scientist in the forestry department of the Experiment Station. “We’re going to let Mother Nature pick them.”
Robert Fahey, an assistant professor in the natural resources and environment department at UConn, who is beginning a forest/climate change research project with DEEP, opts for “complexity” instead of “diversity.”
“More complex age structure; more complex canopy structure. You get more carbon storage – by promoting complexity and diversity,” he said. “It’s often going to be the best way of hedging our bets.”
But how do you achieve that diversity or complexity?
A willingness to experiment
“It is incredibly difficult for the people who steward and manage and maintain forests and take care of ecosystems to be able to incorporate all the information about climate change and other stressors into their management,” Janowiak said. “It’s inherently complex, and it’s essentially unpredictable.”
She said forest managers need to think about climate change impacts in the context of location. And because past management practices may no longer be useful and the future is a pretty big question mark, managers need to be willing to experiment.
Which is kind of what’s happening at the Hoffman Preserve.
Barrett, working with her students, researched the trees that were likely to do well in the future and then settled on planting two types of trees: those that were already established here but had been propagated south of New England, and those that were just beginning to be seen in or near Connecticut.
“We’re not really doing assisted migration — we’re not taking a tree from Georgia and trying to bring it up here,” she said one morning before the May planting. “I just got a shipment at 7 a.m. this morning of oak — black, white and red oak that we have here in Connecticut — but that are from Maryland, so they’re southern genotypes. So that’s going to be interesting to see how they do.”
She also picked trees that are just being seen in southwest Connecticut and on Long Island — liquidambar, redbud, loblolly pine.
“These would be range expansions — something that we would expect would move in,” Barrett said. “And it’s not just 'Can they grow?' It’s 'Can they reproduce here for their long-term survival?'”
But she nixed longleaf pine, whose range is in Virginia and further south, as too far south.
Barrett is aware that modeling for climate change is iffy, so the plan weighs loads of factors: soil, sunlight, location, temperature, wind, pests and wildlife value. It looks at known existing conditions and then factors in what future conditions are likely to be — while acknowledging those conditions could change.
“The wild cards are drought and precipitation,” she said — especially with things like torrential downpours. “So we’re being very careful to put things like a tulip tree — which is found in moister soil — at the bottom of a slope, where it already is moist, to enhance their chances.”
Sumac went in bright sunny areas with dry soil.
Even so, plants are so much more forgiving, Barrett said. “It’s called phenotypic plasticity. They can adapt to certain conditions. Sometimes they’re just not going to make it, but they’re adaptable,” she said.
The UConn/DEEP project involves more straight research than what is happening at Hoffman Preserve. “The general focus is how to promote resilience in forests and what factors make forests more resilient to a variety of stressors,” Fahey said.
The team is still looking for 5- to 8-acre sites in the Mohegan Forest in Scotland. The plan is to apply different strategies to build diversity in the forest — age, species, resilience. And they’ll be planting species that are thought to be climate adaptive, also from the south: Southern red oak, southern hickory, tulip.
“The focus is not so much on shifting species — it’s more about how the forest with different structural and compositional outcomes will adapt to more droughts and hurricanes,” Fahey said. “The goal is not to test out some new species.”
There are other forest and climate change initiatives around the state, some private some public. The New England Forestry Foundation, which has been around since 1944, in the last several years started incorporating climate change into its messaging as it helps landowners and public entities implement forest sustainability measures.
“The urgency of the climate problem is becoming clearer and clearer every month, even every day,” said Frank Lowenstein, the foundation’s COO. “We’re seeing higher levels of mortality already.”
One such effort is MassConn Woods – a collaboration of more than three dozen communities on both sides of the border.
The foundation is also assisting the city of Hartford as it begins climate adaptation planning for Keney Park’s forest — about half the park’s 694 acres. Climate change has been a big consideration, underscored when the park forest experienced four fires in less than six weeks this spring.
“Some species of trees, mainstays of urban and rural forests, are less happy with the way climate is going and they will get less happy as we go along,” said Jack Hale, chairman of Hartford’s Tree Advisory Commission. “Just because a tree has been happy in Philadelphia doesn’t mean the only difference between here and Philadelphia is a couple degrees of heat,” he said of the notion of looking south.
The commission and the city forester are planning new tree-planting recommendations that consider things like drought, floods, snow, heat and fires. The core of their plan is the same as everyone’s: diversification. And they’re thinking more money will be needed to provide more frequent care for trees as the stresses on them increase.
“What we’re planning for is a future that we can’t predict,” Hale said. “We can’t predict whether major hurricane seasons are going to start showing up around here. Or 10 feet of snow on the ground, all on one day.”
But even that prospect, tinged with hyperbole to be sure, doesn’t always have forestry experts fearing the worst.
Waiting for change
“I’m not worried about tree survival,” said Fahey, the UConn professor. “Forests are pretty resilient to a lot of disturbance. They’ll deal with climate change relatively well.”
He and others point out that in the early 1800s, the Connecticut landscape was about 25% forest cover, and now it’s up to more than 60% — actually a bit lower than it was mid-20th century. What worries him more is the conversion of forest land to other uses and the fragmentation of forests. “Trees grow here, they come back — if we don’t turn them into parking lots,” he said.
Robert Askins, an emeritus professor at Connecticut College who has studied deciduous forests around the world, said that, like so much of nature, there’s nothing static about a forest. In the immediate future, he worries about insects and pathogens knocking out one tree species after another, but his long term fear is climate change.
“The big difference may be the pace of climate change,” he added. “The big worry now is it’s happening so quickly — even the very resilient species that have developed in the temperate zone, even they might not be able to keep up.”
While trees are clearly not speed demons when it comes to growth, at the Hoffman Preserve there is already evidence of change, since the patch cuts were completed in the fall of 2019 and a few small plantings were made in 2020, including some seeding along access areas that some local Cub Scouts helped plant.
All kinds of things are popping up that couldn’t grow before because there just wasn’t enough light or nourishment, such as blueberries and huckleberries. Beech trees are sprouting out of stumps — now of concern with beech leaf disease spreading.
“One of the things that we’re seeing that’s really exciting is something call sweet fern. It’s not a fern, but it fixes nitrogen, so [it's] really good for the soil,” Barrett says, taking a break from planting to find the little sprout and sample its pungency.
Pointing elsewhere, she says: “This is a sumac here that’s sprouting. These are ideal conditions for it — open, sunny — so it’ll get 8 to 10 feet and spread over time.”
The open space has also attracted more birds, which bring an ecosystem change. They carry seeds and drop them to become potential new growth. They eat unwanted pests.
“Never, ever have we had bluebirds at the Hoffman,” said Sullivan. “Well, we have bluebirds now.”
Deer guards are being installed to keep deer from doing what they do best: eating plants. And everything will be monitored. To that end, GPS coordinates will be taken for each tree or group of same-species trees so folks can find them again.
Depending on whether they flourish, as many as several hundred more trees may be planted in the fall.
And then everyone waits, and waits. These are trees, after all.
“I don’t know that I’ll be here to see it as a forest,” Sullivan said. “But my Cub Scouts will be.”
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