The Future Forest

RED SPRUCE FOREST

In the high-elevation forests of the Central and Southern Appalachians, the red spruce is king—the foundation of a regionally rare ecosystem and the key to a mutually beneficial forest relationship. Symbiotic fungi in the soil near tree roots help young red spruce grow. Flying squirrels, which soar between the spruce’s upper branches, dig for the fungi’s fruiting bodies (or truffles), eat them and deposit their spores throughout the forests, perpetuating this cycle.

NORTHERN HARDWOODS

In New Hampshire, scientists are testing ways to diversify beech-dominated forests. They fell some trees to let more light hit the forest floor and establish shade-intolerant species. They also plant some trees that may be better adapted to a future climate. Amid the fallen trees in these experimental plots, a host of flora and fauna take root and refuge in the newly decaying matter.

The varied oak, pine, hardwood and spruce forests that repopulated the North had a high tolerance to cold. But because there was a small number of hardy pioneers that could survive a newly available environment, some species lacked genetic diversity. Without this variation coded across their genes, species have fewer chances to adapt to changes—something they need now as the climate goes a bit haywire and diseases spread more rapidly.

Lougee’s team has partnered with the University of Vermont, New Hampshire Fish and Game Department, and Northern Institute of Applied Climate Science to set up a forest management experiment in 1,300 of the 5,500-plus acres of Green Hills. They strategically cut down trees to open up the forest canopy, which encourages a greater diversity of shade-intolerant species, such as oak and pine, to fill in. The team leaves behind some large felled trees to support diversity as wood decays and pushes over dead trees to create “tip-up mounds,” which create microclimates for a range of organisms.

The team is also planting a variety of tree species, some of which they’ve culled from regions farther south. The process, known as “forest-assisted migration,” has at times been a controversial method, generating debates among conservationists about how much to intervene on nature’s behalf and what unknown consequences may ensue.

Researchers hope that future resilient forests will be able to more rapidly recover from climate-driven threats on their own. Many of today’s plants and animals must head northward or to higher elevations (or both) to survive as their habitats change, and the Appalachians offer a natural highway to do so. Some species’ ranges in the eastern U.S. have even been reported moving an average of 6 miles north and 7 miles west per decade since the 1980s. During periods of intense climate change in Earth’s past, plants and animals had a greater ability to trek across landscapes than they do today. Now, the range is fragmented by cities, roads and other human-made blockades. More troubling, the pace of change is unprecedented, making it challenging for life such as trees, which grow in specialized conditions and have limited control of seed dispersal, to keep pace.

Lougee’s team is expanding the northern range of some select saplings in their experimental plot. “The idea here is not to [cut down and] replant the future forest,” Lougee says, “but really just get a few species established that can be a source of seeds in the future.”

The project started in 2023, so there are few results yet. But Lougee’s team has its eyes trained ahead as it tests how conservationists and forest managers can support diverse forests in the Northern Appalachians that can better adapt to the future climate. And as the plight of the tree species that repopulated the Northern Appalachians shows, diversity isn’t just about a greater variety of many species—it’s also important to encourage genetic diversity within individual species so some might have a chance to endure the changes to come.

HEMLOCK FOREST

More than 100 species rely on the mighty hemlock forests—including many birds and bats in migration corridors like Pennsylvania—but a fast-moving microscopic invasive pest called the hemlock woolly adelgid threatens their survival. In a warming world, invasive pests with few predators can spread rapidly. In some places, land managers must rely on pesticides to battle pests like the adelgid.

OAK HARDWOOD FOREST

The Southern Appalachians are the most biodiverse region in the world for amphibians. Numerous frog and salamander species—some extremely rare—rely on these tracts of land where vernal pools, or temporary ponds, host breeding grounds each spring. Conservationists are working to ensure the diversity of trees in the oak-hickory forests of this region by using controlled burns and other methods to reduce faster-growing poplars and other trees that crowd and shade out the mighty oaks.

“We all inherently know the variability of ecosystems within just the Central Appalachians,” Lorber says. “But here’s a chance to use the same filter of climate resilience to look at different ecosystems’ strengths and weaknesses. That could begin to guide the type of work we prioritize.”

For red spruce forests, this framework highlights their lower biodiversity and climate-adaptive capacity as risks for climate resilience. But, as is true for humans, even a single species like red spruce can have a range of genetic diversity. Shallows’ team is now drawing on that potential diversity within red spruce to increase the resilience of the region’s forests.

In partnership with researchers at the University of Vermont and Central Appalachian Spruce Restoration Initiative, Shallows’ team has been planting a genetically diverse stock of red spruce seedlings nearly every year since 2019, primarily on public lands like the Monongahela National Forest in West Virginia and the Clinch Mountain Wildlife Management Area in Virginia. The foresters intentionally select seed stock from sites with greater genetic diversity to enhance its climate-adaptive capacity—and give it a greater chance of survival—at restoration sites. And University of Maryland researchers have built a computer model to identify ideal seed sources from different ranges and regions in another aspect of assisted migration called “assisted gene flow.” This model looks at the future climate period, the estimated greenhouse gas emission level and location details like latitude and elevation to pinpoint seed stock that can likely survive in altered future conditions.

Shallows’ team plants a combination of these seedlings, knowing some individuals may thrive and some may fail, with hopes that the ecosystem as a whole survives and adapts over time.  

Climate predictions, Shallows says, point to the region becoming drier and hotter overall, but it’s not known how seasonal rainfall patterns will change. “Plants will need to adapt to increased variability in their environment,” she says. “So, what we’re trying to do is buffer the system as best we can for all the unknown factors.”