At Hoffman Evergreen Preserve in Stonington, Connecticut, southern trees are growing in forest clearings. Where dense stands of hemlock once shadowed the ground, the terminal buds of loblolly and Virginia pines poke out from the tops of 6-foot deer guards. Sweet gum and tulip poplar saplings rise above the clipped stems of gray birch.
The trees are part of an effort to assist range expansion of heat-tolerant species in one of the most rapidly warming areas of New England. Through this project, Avalonia Land Conservancy, the regional land trust that owns the preserve, aims to improve current habitat while also accelerating the preserve’s adaptation to climate change.
Located six miles inland from Long Island Sound, Hoffman Evergreen Preserve is Avalonia’s largest property in Stonington. The preserve started with 142 acres donated in 1976 by Chippe Hoffman, who with her late husband Robert had owned the land since 1958. Robert had an affection for Canadian forests, derived from time spent living and working in Ontario and Quebec. On his Connecticut land, he planted many stands of white pine, red cedar, and eastern hemlock – all native to coastal Connecticut – as well as non-coastal species: tamarack and spruce.
Avalonia has since acquired adjacent forested lots, increasing the holding to nearly 200 acres. For decades, the preserve has served as a much-loved community recreation area. Dog walkers and hikers enjoy more than four miles of trails through mixed hardwood and softwood stands. Along the way, they pass by evidence of the land’s history as a nineteenth-century farm, including stone walls and a family cemetery, where the oldest headstone, erected in 1827, honors a veteran of the Revolutionary War.
Until recently, Avalonia has taken a mostly hands-off approach to forest management, maintaining trails and monitoring tree health, but refraining from timber harvests or other major interventions. This mostly passive approach made practical sense for an almost-all-volunteer organization and jibed with the preferences of many of the preserve’s frequent visitors, who cherish the preserve and do not want to see it change.
Change, however, is occurring at an alarmingly rapid pace in coastal Connecticut. As shown through the National Oceanic and Atmospheric Administration (NOAA) “Climate at a Glance” online mapping tool, the average temperature for New London County, where Stonington is located, rose by 3.3 degrees Fahrenheit between 1922 and 2022, with all but one of the top 5 hottest summers occurring in the past 10 years. This rise is significantly higher than that of most areas of New England. (For comparison, Grafton County, New Hampshire, where the Northern Woodlands office is located, has experienced a 2.7-degree increase in that same time span.) A 2019 report from the Connecticut Institute for Resilience & Climate Adaptation (CIRCA), a University of Connecticut resource, estimated that the state as a whole is likely to experience another 2-degree rise in average mean temperatures by 2050.
According to Beth Sullivan, who chairs the committee responsible for overseeing Avalonia’s Stonington properties, damaging impacts of climate change at the preserve began to be noticeable in the early 2000s. It was about that time, she said, that “the woolly adelgid came in and really wreaked havoc on hemlocks.” There was escalating harm from other invasive insects, too – some new to the region, others already on the landscape but causing new damage. These included hemlock scale, spongy moth, winter moth, and emerald ash borer, which devastated the preserve’s ash trees.
Droughts, bouts of heavy precipitation, and more frequent, intense storms, including Tropical Storm Irene in 2011 and Hurricane Sandy in 2012, also took a toll. Strong winds broke tree stems, knocked down trees, and carried salt spray into the forest (salt is especially harmful to white pines).
In addition to seeing climate change effects, Sullivan and other Avalonia volunteers were troubled by the lack of diverse wildlife habitat, including the absence of low-level vegetation necessary for many forest birds. Heavy deer browsing and crowded stands left many areas of the forest floor dark and barren, with poor prospects for regeneration. “The hemlock stands were almost like grass, they were so thick,” recalled Sharon Lynch, a retired George Washington University professor who serves on Avalonia’s board of directors. “There was no understory. It was completely closed in.”
As forest conditions continued to decline, and concerns about visitor safety from hazard trees increased, Avalonia leaders began to explore active management options. In 2018, after multiple consultations with forest ecology experts, including a free assessment by Connecticut Audubon, the Avalonia board of directors contracted Hull Forest Products to clear five patch cuts (a total of a little more than 6.2 acres) and to selectively thin other areas, with a focus on removing dead and dying trees. In order to pay for the project, Avalonia and Hull planned for a timber sale. Work was scheduled to begin in autumn of that year, but in yet another example of climate change disrupting expectations, soft ground conditions that winter necessitated a delay. The cut went forward in autumn 2019. All told, approximately 60 acres of the preserve were affected, including patch cuts, thinned areas, and skid trails.
Lynch noted that Hull managed the project in a careful and professional way. But inevitably, the spectacle of a logging job’s aftermath came as a visual shock. As Juliana Barrett, an ecologist affiliated with the Connecticut Sea Grant Program at the University of Connecticut, noted in a later writeup about the property, “Many of the visitors to this well-used preserve questioned the tree cutting, and voiced a wide range of concerns about the management actions.”
Whether and how to cut was a difficult decision for Avalonia’s leaders. A second decision, to move forward with climate change–focused plantings, was in many ways more complicated to implement, but far less controversial. Coinciding with the worst period of the pandemic, the project provided local residents with an opportunity to gather outside for a shared purpose, at time when most community events were unavailable.
In winter of 2019, Sullivan and Lynch began talking with Barrett about Hoffman Evergreen Preserve’s future. Lynch, who was working with the National Science Foundation at the time, had discussed the concept of assisted range expansion with biologists there and brought that idea into the conversation. In essence, assisted range expansion involves moving species slightly beyond their historical range – replicating a dispersal process that would likely happen naturally during a longer time period. By accelerating this shift for forest trees and shrubs, Avalonia could, in theory, help to maintain long-term biodiversity and forest structure, even if some native species (such as hemlocks) suddenly declined.
The group’s interest in assisted range expansion led to discussions with Christopher Riely, a Rhode Island forester who had a leadership role in introducing southern species at Providence Water, the forest that surrounds that state’s main reservoir. The group also sought advice from Maria Janowiak from the Northern Institute of Applied Climate Science, who provided guidance and recent research on tree species’ responses to climate change.
Working with UConn Extension forester Robert Ricard, Lynch, Sullivan, and Barrett crafted a grant proposal for a habitat restoration project, which included educational outreach to the community. Long Island Sound Futures Fund supported the project, and in spring 2020, just as the pandemic took hold, implementation began. The first step was researching specific site growing conditions at the preserve’s patch cuts. Two UConn students, Chris Arrotti and Griffin Licari, took on this work, documenting soil type, slope, existing vegetation (including any invasive plants), and other features. The students then used this information and U.S. Forest Service vulnerability assessments for the Northeast and Mid-Atlantic to draft a list of recommended tree and shrub species they thought would work well at the preserve. The list included both southern species and some native ones, such as oaks, that seemed well suited to future climate conditions.
Barrett and Ricard reviewed the list and also sought outside feedback, including from the state botanist. The final list included pagoda and gray dogwood; smooth sumac; common persimmon; pignut hickory; tulip tree; black tupelo; sweet gum; American hornbeam; red, black, and white oaks; redbuds; and downy serviceberry. The mix also included a small number of Virginia pine and loblolly pine, partly as a way to honor Robert Hoffman’s passion for conifers. Avalonia sourced the trees and shrubs both locally and from the Maryland State Nursery.
For Lynch, the most intriguing part of this list was the native trees, such as red oaks, sourced from Maryland. “This is what I think is really cool,” she said. “Red oaks on the southern end of the range just might have some adaptation specific to that warmer climate.” By importing these southern phenotypes, she explained, “You aren’t really looking to replace the trees here. You’re looking to assist the expansion of the gene pool. They really could help. There’s no way of knowing, but that to me is a really interesting idea.”
The plantings took place during 2021 and 2022. Volunteer work crews, organized by Sullivan, spent hours digging through rocky soil and hauling water. On other days, volunteers showed up with clippers and weed trimmers to cut back the gray birch saplings that threatened to engulf the clearings. “Beth’s ability to call on a team of volunteers is phenomenal,” said Barrett. “She put out the call, and all these people showed up.” What was especially gratifying about this volunteer response, she said, was the diversity of people who came out, everyone from retired octogenarians to a Cub Scout troop and their parents, who took on the special task of seeding the skid trails with grasses and herbaceous perennials.
As all this work was proceeding, Avalonia and the Connecticut Sea Grant were also hosting educational events, including a four-day workshop that attracted forest managers from as far away as Maine. Connecticut College students, working with Sullivan, developed educational signage, which was also supported by the Connecticut Sea Grant. Lynch put together a well-received, four-part webinar series, hosted by UConn, that drew both a local and national audience.
How this project will play out in the long term is, of course, unknowable. But so far, said Barrett, most of the planted trees and shrubs seem to be doing very well. During a September 2023 visit to the preserve, Barrett and Lynch were pleased to see how green the clearings looked, both from the plantings and the native seed bank taking advantage of new light. This new growth has already had a noticeable positive effect on the diversity of birds in the area and likely is helping promote other wildlife, too.
As part of this project, Barrett has maintained detailed spreadsheets, logging the GPS location, species, source, and planting date of every tree and shrub. She hopes this data can serve as a basis for five-year interval checks and, perhaps, inform new work, as volunteers observe how warming weather impacts the preserve in the future. “We have to acknowledge that our climate is changing, in so many ways,” she said. “We have to be proactive in every aspect, too.”
To check out the UConn webinar series, click here and scroll down to Finding the Right Trees for the Right Time.