Creating a Climate-Resilient Forest at Tug Hill

Click here for more information on The Nature Conservancy’s Tug Hill project. Photo by Brian Roat/Courtesy TNC.

Just east of Lake Ontario and west of the Adirondacks lies the Tug Hill Plateau, a chunk of sedimentary rock that rises from an elevation of 250 feet at its base near the lake to 2,100 feet on its eastern side, where cliffs drop steeply to the Black River. A 1.2 million-acre mosaic of public and private lands, Tug Hill is the third largest forested area in New York – after the Adirondacks and Catskills regions – and is composed primarily of northern hardwoods, with red spruce common in wetlands.

From this forest spring the headwaters of the Sandy and Fish creeks and the Salmon, Mohawk, and Deer rivers. Gorges carved by glacial meltwater cut through the plateau, with rivers descending into spectacular waterfalls. The woodlands of Tug Hill are a crucial link for wildlife moving between the Adirondacks and the southern Appalachians. Mammals such as black bear, bobcat, marten, and fisher, and forest birds including Blackburnian warblers and three-toed woodpeckers make their home here. Tug Hill forests also support a vibrant recreation economy, some 7,000 jobs in the timber industry, and clean drinking water for many towns.

Tug Hill is legendary for its heavy annual snowfalls. On average, the area receives 200 inches of snow per year – more than any region east of the Rocky Mountains except for a few isolated pockets – due in part to lake-effect snow generated by arctic winds sweeping over Lake Ontario. (The village of Hooker holds the state record for annual snowfall, with 466.9 inches – nearly 39 feet – during the winter of 1976–77.) However, these deep snows may diminish. Climate models predict that the Tug Hill Plateau will warm by 4.4 to 6.4 degrees by the 2050s, with shorter winters and more precipitation falling as rain or freezing rain. Climate scientists believe these changes will eventually alter the composition of Tug Hill forests and may lead to declines in particular tree species such as balsam fir and red spruce. In addition, insect pests such as hemlock and balsam woolly adelgid are likely to thrive in warmer winters. Tree mortality may be higher in stands that lack age, structural, and species diversity.

Because of the ecological importance of this region, The Nature Conservancy in New York has invested heavily in land conservation here and owns or manages nearly 17,000 acres on the Tug Hill Plateau. The Conservancy has also launched a reforestation effort here, planting thousands of tree seedlings on a 400-acre tract of land that it owns near the village of Turin – land formerly owned by a paper company. The primary goal of this project is to create a “living laboratory” to study ways to make forests more resilient to climate change. Long-term goals are to improve the health of this forest and to reestablish a mature forest, a forest type scarce on Tug Hill.

Restoring Mature Forest

On a sunny morning in May 2020, several vehicles rumbled down a 20-mile-long gravel road to the Turin property and parked at a former log landing. Chris Zimmerman, forest restoration ecologist with The Nature Conservancy in New York, was part of this convoy. Also on hand were the Conservancy’s Northern New York Conservation Lands Manager Brian Roat, Stewardship Coordinator Paul Gallery, and Robert Smith, restoration coordinator for the St. Lawrence-Eastern Lake Ontario (SLELO) Partnership for Regional Invasive Species Management. As the group walked up an old skid road into the woods, warblers sang from the treetops, and red trillium nodded in the breeze.

Robert Smith, SLELO restoration coordinator, sets pin flags to mark locations for tree seedlings at Tug Hill. Photo by Chris Zimmerman/Courtesy TNC.

The team carried 2-foot-tall, colored pin flags and clipboards with data sheets attached. They were here to mark locations for a large-scale tree planting of more than 8,500 seedlings in a series of small clearings.

The timber on this tract of land was cut multiple times during the past 100 years, and the forest that has grown back is relatively young, even-aged, and suffers from beech bark disease. In this project – funded in part by the Wildlife Conservation Society’s Climate Adaptation Fund (established by a grant from the Doris Duke Charitable Foundation) and the SLELO Partnership for Regional Invasive Species Management – the Conservancy aims to regenerate underrepresented, native, climate-resilient species and to create a diverse, uneven-aged woodland with big trees, snags, and large downed logs – all characteristics of an older forest.

Preparing to Plant

Prior to the 2020 planting, the Conservancy had made a quarter to one-and-a-half-acre patch cuts in areas with a high percentage of beech bark disease, similar to the types of openings produced by natural disturbance. They retained mature trees, left fallen logs and other woody debris on the ground, and girdled some trees to create snags for wildlife habitat – all steps to increase the structural complexity of the forest. During the next four days, Zimmerman and his colleagues established transect lines with a compass and created a grid. They placed the 8,500 colored flags – one for each seedling to be planted, with different colors for each species – according to the random, computer-generated design on their chart.

Four tree species would be planted here: sugar maple, white pine, red oak, and white oak. Although pine and oak grow in the region, they were not present on this property prior to the Conservancy’s plantings, and maple was underrepresented here. In a planting on this land a couple of years earlier, oaks had a much better survival rate than other species after a record drought. Weather volatility was also evident in 2020. During the last day the team placed flags in May, it snowed two inches. Two weeks later, when a local contractor arrived for tree planting, the temperature had reached 90 degrees. These drastically changing conditions “highlight the uncertainty and variability of our climate future,” said Zimmerman.

Graduate student Miriam Wolpert plants bitternut hickory saplings at Second College Grant Forest. Photo by Peter Clark.

To prepare for the planting, Conservancy staff had worked with Tony D’Amato, professor of forestry at the University of Vermont (and a Northern Woodlands board member), to develop the planting design. D’Amato has been involved with experimental trials for climate adaptation on Dartmouth’s Second College Grant Forest in New Hampshire and is helping to monitor the Tug Hill project. He describes both efforts as “ecological silviculture,” a process to determine how best to help forests survive and adapt to climate change. The Northern Institute of Applied Climate Science (NIACS), Cornell University, and the SUNY School of Environmental Science and Forestry are also consultants to the Tug Hill project.

In 2021, one year after planting, the survival rate of the new seedlings ranged from 60 to 85 percent, with red and white oaks again showing higher survival rates than maple and pine. The Conservancy will continue to monitor the forest over time, and will measure carbon accumulation.

Drawing on lessons learned from the Tug Hill Project, Zimmerman and colleagues, in partnership with NIACS, have produced a publication for private landowners titled “Healthy Forests for our Future: A Management Guide to Increasing Carbon in Northeastern Forests.” The guide describes climate-smart forest management practices for northern hardwood and oak-hickory forests in New York State and in southern and central New England, with a focus on carbon benefits. Because so much of the Tug Hill Plateau is in private ownership, the Conservancy has concentrated on work with private landowners.

Experimental Trials in New Hampshire and Vermont

The work at Tug Hill has been informed by research on the Second College Grant, a 27,000-acre forest in northern New Hampshire owned by Dartmouth College since 1807, which is one of 11 sites participating in Adaptive Silviculture for Climate Change, a growing collaborative effort by scientists and managers to conduct experimental trials in different forest ecosystems across the United States and Canada and to study their responses to climate adaptation actions. The University of Vermont (UVM), Dartmouth, the USDA Forest Service, the Northeast Climate Adaptation Center, and the state universities of New Hampshire, Maine, and Massachusetts are all partners on this project, now in its seventh year. “We don’t have the answers” to how to help forests adapt to climate change, said D’Amato. “What we’re hoping over time is that we come up with some combinations that will sustain the forest.”

On 400 acres of the Second College Grant (200 acres of northern hardwoods and 200 acres of red spruce-northern hardwood), four major research areas have been established. One is a control area, where no management is taking place. The second area is receiving light management, called a resistance strategy, intended to improve the forest’s ability to resist changing conditions. Management in the third area includes resilience strategies designed to increase the diversity of the forest, including the size, age, and species of trees, and to provide multiple pathways by which the forest could recover following climate or disturbance impacts.

In the fourth area, management is actively creating change to encourage adaptive responses, a strategy often called transition. For example, researchers are cutting small clearings and planting these with tree species not currently abundant in the forest, including species common farther south and likely to do better in a warmer, drier climate. These include northern red oak, bitternut hickory, eastern hemlock, basswood, black birch, and chestnut. The chestnut trees are a hybrid of a strain of blight-resistant American chestnut and a Chinese chestnut.

“We are not trying to re-engineer the forest,” explained D’Amato, “but are trying to increase the diversity of the forest on a limited scale by planting a seed source.” From this source, scientists hope the new, more climate-resilient species will spread to the rest of the forest, especially as the climate continues to change over time.

The Tug Hill Project and the research on the Second College Grant Forest have stimulated other projects to promote climate resilience in forests. For example, UVM and Dartmouth College are setting up an experiment planting climate-resilient species on Dartmouth’s 509-acre woodlot in Corinth, Vermont, which is currently 40 percent white ash. Most of the ash at this site is expected to succumb to emerald ash borer in the near future, as this invasive pest spreads in the area.

The Nulhegan National Wildlife Refuge in Vermont’s Northeast Kingdom has a high proportion of balsam fir, a species vulnerable to climate change. Here, the U.S. Fish & Wildlife Service is working with UVM, the Conservancy, and other partners to diversify forest composition and structure and planting other species to sustain wildlife habitat.

Back at Tug Hill, winter is in the air again. The hardwoods have formed winter buds and lost their leaves. Many of the birds have flown south, and bears have gone to ground. Snowshoe hare and ermine have turned white. The wildlife, trees, and other plants here are well adapted to cold, wind, and snow. Cross-country skiers and snowmobilers are looking forward to the deep snows of winters past. For how many more years will the cold and snow keep coming? No one really knows.

“There is no guidebook for preparing our forests for a changing climate. But in Tug Hill we have the perfect site for identifying solutions to keep our forests healthy and strong,” said Zimmerman.