The Fading Forest, Part III


When a tree dies, it opens a hole in the canopy that allows invasive species to thrive. (Photo by B. Cronin)

Ash, beech and hemlock trees are being threatened by causes known and unknown, changing the forests of the Highlands in drastic, and dangerous, ways

For the most part, the 3,194 acres of Black Rock Forest across the Hudson River in the western Highlands are not old-growth forest. Much of it was pasture and farmland cleared in the 18th century: One of the main roads through the forest, Continental Road, dates to the Revolutionary War.

There are, however, a few places that predate European settlers. There’s Mineral Springs near the forest’s southern border, shrouded in hemlocks which have stood since before the signing of the Declaration of Independence, only to now be stripped bare by an invasion of hemlock woolly adelgid. There’s a labyrinthine oak, hundreds of years old, at the intersection of Continental Road and a hiking trail.

About a century ago, early environmentalists attempted to return the fields to the forest.

“They put white spruce over there,” says William Schuster, the executive director of Black Rock Forest, as we walked down Continental Road in the fall. “Red pine over here. They started a lot of experimental things, too, and where they didn’t plant, deciduous species [that shed their leaves each year] like ash came in. They’re fast-growing, require high light, and they’re part of this ecosystem anyhow.

“That’s why we had so much ash around here,” he said, “and why this is the area that, for us, has been the most devastated by the emerald ash borer,” another invasive pest.

The ash trees of Black Rock were once used by craftspeople to make everything from tool handles to Adirondack-brand baseball bats. But the grove that we’re approaching has been cut down, a victim of the borer. In its place, the foresters of Black Rock are working on an experimental project they call Patron’s Grove.

creating Patron's Grove

Foresters are creating an experimental grove at Black Rock Forest. (Photo by B. Cronin)

The new grove addresses several issues. It will be a place where donors can have a tree planted in memory of a loved one. It will serve as a sort of internal arboretum, showcasing at least one example of all of the native plants and trees that can be found in the forest. And, as best it can, the grove will play defense.

When the dying ash trees were cut down, it created an opening in the canopy, allowing light to reach the ground and whatever is there to flourish. If you’re not careful, what emerges from the earth below may be headaches.

A forest under siege

Matthew Brady is a second-generation forest manager at Black Rock. His father, John, was the forest manager for 35 years, and his brother, Ben, works here as well. As forest manager, Brady was responsible for cutting down the dying ash to make way for Patron’s Grove; he sent them to a sawmill. They will probably be the last ash trees milled from Black Rock in his lifetime.

Because foresters at Black Rock want to have a robust ecosystem dominated by native plants, Brady spends a lot of time tracking the encroachment of invasive species such as burning bush, which is encroaching from Route 9W.

“The more I look for burning bush, the more I see it,” Brady said. “That’s a pretty tedious one to kill.” He notes that the mile-a-minute weed is “only in one spot, but it will not die.” For Devil’s Walking Stick plants, a crew from the New York-New Jersey Trail Conference Invasives Strike Force helped him rip out more than 600 stems. When they checked this year, they found success: 99 percent hadn’t returned.

Less successful have been efforts against knotweed (which Brady and Schuster agree is a lost cause) and stiltgrass, which has been in the forest since the 1990s.

Fast-growing stiltgrass can quickly take over. (Photo by B. Cronin)

“I remember the first patch of it, up at the upper reservoir,” said Schuster. “Somebody suggested we should get rid of it, and I thought, ‘Ah, it’s just one patch.’ Now, by stem, it’s probably the most common species in the forest.”

Brady, pointing 20 feet overhead, added: “It’s even growing out of the crotch of that tree. There’s no stopping it.”

And then there’s Japanese barberry, prized for its resistance to deer, cursed by foresters and naturalists because of its rapid spread, especially when it finds holes in the canopy. At the Minnewaska State Park Preserve in Ulster County, the stands of ash trees near the Split Rock swimming hole were rapidly taken over by barberry as soon as the ash trees died.

At Black Rock, Brady said if he notices any Japanese barberry while driving the Bobcat on forest roads, he’ll turn the excavator around to rip it out. “That gives me some satisfaction,” he said.

At Cranberry Lake Preserve in Westchester County, Taro Ietaka, a Cold Spring resident who is a parks supervisor for the Westchester County Department of Parks, Recreation and Conservation, faces many of the same challenges because of dying ash and beech. He is considering planting oak and maple with the hope that, once the ash and beech have died, the new trees will block barberry, Tree of Heaven and other invasives.

As he explained this, soft pops could be heard ringing through the forest — bottle rockets being shot at the nearby Kensico Reservoir by the New York City Department of Environmental Protection to scare away flocks of Canada geese before they befoul the city water supply.

At some point, seeing all this effort, with explosions, sprays, injections and excavations, with the beetles sucked through tubes and strike forces roaming the woods to rip out aggressive weeds, you start to ask uncomfortable questions, such as, is this all worth it?

Darwin’s last laugh

When I spoke to environmental journalist Elizabeth Kolbert, who won a Pulitzer Prize for her book, The Sixth Extinction, before she appeared via Zoom on Dec. 6 at a Desmond-Fish Public Library event, I asked which environmental issues she felt weren’t getting enough attention. She replied that, while scientists are well aware, most of the public doesn’t realize how much warming because of climate change is already “baked into the system.”

“That is why scientists have always said that you have to act before you don’t like the climate that you’re seeing,” she said. “Because you’ve already baked in a lot of damage because of the time lag in the system.”

Even if humanity were able to immediately stop emitting greenhouse gases, we are still going to suffer from increasingly warming temperatures, rising seas and other global upheaval. The effects we are seeing now are only the beginning. In addition, the global system of trade that has facilitated the spread of invasive plants, insects, viruses and pathogens will continue. We continue to alter ecosystems in countless ways that are both known and yet to be realized.

spraying trees

A state forester applies insectiside to control a hemlock woolly adelgid infestation at Lake George in the Adirondacks. (DEC)

If, as Darwin proposed, nature is a never-ending competition, where only those that can adapt to changing conditions survive, why attempt to restore a fallen world? Why try to save species that cannot adapt fast enough to the global economy and climate change, and let those that can run wild and free? Why even refer to them as “invasives,” which implies a nefarious intent by insects and plants that are simply taking advantage of environments they can thrive in? If ash, beech and hemlock trees can’t survive in the 21st-century Highlands, why not let them die?

“If we lost every beech tree, it would still be a beautiful forest,” says Ietaka at Cranberry Lake. “But we’d lose that diversity.”

Schuster, standing where Black Rock’s last ash grove used to be, said that to surrender would be to give up on the world, instead of preserving it to our children and grandchildren. “We’ve lost so much,” he said. “We’ve already lost main species, medicines, organisms that are adapted to this specific environment, the colors in the fall.”

Mark Whitmore, the head of the New York State Hemlock Initiative, said, “I’m not going to sit by and watch our native trees suffer as a result of somebody’s ignorance.”

Brent Boscarino, who coordinates the Invasive Species Citizen Science Program for the New York-New Jersey Trail Conference, noted that the reason to fight is that you otherwise will end up with a “monoculture.”

“There’s a clear link between invasives and decreasing overall biodiversity in an ecosystem,” he said. “When fast-spreading, all-encompassing invasives like barberry and stiltgrass take advantage of newly opened canopy, the forest can’t support the higher trophic levels that are either using it as habitat or feeding on it, so that limits the number of species that can be living in an area.

“Just like invasives taking over, all it will take is one disease or one big shift or weather event that could wipe it all out. That’s why diverse ecosystems are more resilient and able to withstand other changes that could be coming down the road.”

American beech

Fagus grandifolia. Sturdy, imposing tree. Typically 50 to 80 feet but up to 120 feet. Smooth, light gray bark. Rounded crown of spreading, horizontal branches. Produces edible beechnuts.

Eastern Hemlock

Tsuga canadensis. Evergreen with conical crown of slender, horizontal branches that often droop. Typically 40 to 70 feet but up to 100 feet. Bark was once a source of tannin in the production of leather.

White ash

Fraxinus americana. Dense, conical or rounded crown of foliag. Typically 75 to 120 feet. Deciduous with dense branching pinnate leaves, and early fall color. Wood particularly suited for baseball bats, tennis racquets, hockey sticks, polo mallets, oars and playground equipment.

Source: Lady Bird Johnson Wildflower Center (

Lose the hemlocks, the ash, the beech, and you also lose the species that depend on them. “Generalist” species that can quickly adapt to changing, even horrific conditions (such as rats, raccoons, pigeons and, yes, humans), are thriving at the expense of “specialist” species that depend on a certain plant or insect to survive, Ietaka noted. Established forests also capture and store carbon; anything that damages them will release tons of carbon into the atmosphere, contributing further to global warming.

Invasive plants may have other characteristics that make them dangerous. Barberry is a home for black-legged ticks, which spread Lyme disease. The sap of giant hogweed, another invasive, can cause severe burns. Tree of Heaven is home to the spotted lanternfly, yet another invasive insect that can kill any smooth-barked tree.

“That’d be almost all our trees,” said Brady.

There are other, surprising, consequences to the accelerated loss of tree life. Bryan Quinn, the owner of One Nature, an environmental design firm in Beacon, noted that in 2017 and 2018 a hydrologist assured city officials there was enough water to support a burst of new development.

Beacon’s main source of water is a reservoir atop Mount Beacon that is surrounded by trees. “What happens if 50 percent of the trees up there are dead?” asked Quinn. “What does that do to water run-off, water quality, groundwater recharge?”

Perhaps it isn’t useful to think of the world as a binary system, either saved or fallen, native or non-native. “I think,” said Quinn, “there’s a middle path.”

The future forest

Quinn said he hopes that the ashes, beeches and hemlocks of the Highlands can be saved. But he’s thinking ahead to a world in which they’re gone or nearly gone. If the climate of the Highlands in 2050 will be more like Virginia’s today, perhaps it’s time to consider what grows in Virginia.

Quinn and his staff, after reviewing scientific papers that examined which plants and trees will adapt better to a rapidly changing climate, decided to conduct a test run. A client offered land for them to plant four “test forests” of about 50 trees each.

Each forest represents a Highlands microclimate, he said, including one adapted for Eastern Hemlock. But Quinn didn’t plant Eastern Hemlocks because of the threat of hemlock woolly adelgid. Instead, he imagined what the hemlocks of tomorrow will be by referencing research on resilient plants and considering trees similar to Eastern Hemlocks whose growth ranges extend just as far north as the Highlands.

“There is overlap,” says Quinn in regard to the forests of Virginia and our local forests. “What can we pull from there to make the forest of the future here, without cutting things down? Let’s seed trees that can reproduce and add to the mosaic.”

Although the test forests are only a few years old, Quinn said he has had success with Loblolly Pines, Virginia Pines and American Holly, the latter of which Quinn found growing wild on Mount Beacon. These are evergreens that supply many of the ecological benefits of Eastern Hemlocks. It’s also likely that insect and fungal pests from warmer U.S. climates will probably spread north, so it may be worth introducing plants that co-evolved with those pests and resist them naturally.

Then there are ghosts of the forest that are ready to return. After being almost gone for more than 75 years, the American Chestnut could make a comeback. Scientists at the State University of New York have developed a genetically modified American Chestnut that can withstand the blight that once wiped it from the landscape. Even Schuster, at Black Rock, who takes such a conservative approach to forest management that he decided to forgo insecticide injections into the forest’s hemlocks, is giddy at the prospect. He points out an area of the forest where the roots of old chestnuts still send up shoots, although they don’t survive to become trees.

emerald borer map

A map created by the Ecological Research Institute shows areas between Greene County and Westchester where the emerald ash borer was detected in 2010-12 (pink), 2013-14 (green) and 2015-19 (blue). The percentages are the number of ash trees killed. The Highlands are located to the immediate east of the green oval at bottom center.

Quinn believes that “return of ecological energy” provided by the revival of chestnuts is sorely needed. They are big trees that “grow quickly, create so much food, so much energy, so much life depends on them.”

There are other shoots of hope. At Cranberry Lake, Ietaka mentioned the Asian long-horned beetle, which appeared in New York City in the 1990s. The city last year declared that the bug has been eradicated from the five boroughs. If they hadn’t, said Ietaka, gesturing around him, “this could have been the Northeast version of the Great Plains.”

Walking through Cranberry Lake, Ietaka pointed out the roots of trees along the trails. He’s spoken to other park managers who have, in the months since the COVID-19 shutdown began, seen more tree roots than usual because the number of hikers has increased so much that trails are being compacted. “For years I’ve been advocating for people to get outside and experience nature,” he says. “And now I’m like, ‘Ahh! Too much!’ ”

But like the lost ash trees at Black Rock that made way for a new grove, this crisis could be put to good use. More people are turning to the outdoors for recreation and for solace; the hope is that a newly engaged public can be enlisted to save the forests they’ve grown to appreciate.

That can mean learning to identify hemlocks, ash and beech trees so that they can keep an eye on them, or volunteering to stop the advance of invasive plants. Ietaka says that after watching the climate crisis grow worse over the past 20 years, it never ceases to amaze him how many people show up on their days off to fill garbage bags with weeds.

Part I | Part II | Part III

Comments are closed.