Where there was once deep shade, there are patches of sun.

Mighty oaks are falling, ashes are disappearing, beeches are dying.

The Connecticut forest is becoming transformed by drought, invasive vines, insects brought here by a globalized economy and climate change, fires, deer, all making our trees vulnerable.

“Trees need water to live,” said Heather Dionne, Hartford’s city forester. “We’ve had several seasons of drought. The oaks are taking a big hit, which is unfortunate because we have so many big oaks.”

Dionne and her three field staff are in constant motion, having to monitor or remove dying or dead trees throughout the city. “We do have another position open, but we’re having a really hard time recruiting,” she said. “Pay is very low. Very, very low.” 

The city hires outside companies to help with all the work.

“I’ve got a contractor in Elizabeth Park right now doing a bunch of pruning and taking out dead trees,” Dionne said. “I’ve got another contractor that I’m overseeing working at Keney Golf Course doing  pruning and such. We’re just trying to keep on track.”

Goodwin Park was gone over two years ago, “but now there’s a few new dead trees in that park that we have to get out of there,” Dionne said. “And then we still have our cemeteries, so getting my team into the cemeteries … There’s a lot of deadwood. And then just the resident requests.”

Dionne and her team are responding to the problem by planting “more climate-resilient species. They’re not all native but they are able to handle the conditions.”

They include London planetree, honey locust, Japanese pagoda trees, tulip trees, Kentucky coffeetrees, yellowwoods.

“We do plant quite a few oaks,” Dionne said. “Oaks are really one of my go-to’s for shade trees.” In addition to white and pin oaks, the city plants swamp white oaks, Northern red oaks and scarlet oaks, she said.

“Another issue that we have in Keney Park is the amount of deer and them browsing on our regeneration, our new oaks (growing from acorns) that are so important,” Dionne said. “There’s very little of that in the park just because of the amount of deer browse.”

Fires, increasing because of the greater amount of dry brush, are another issue, so the city has acquired three vehicles to help put them out.

Beside planting trees and removing dead ones, the forestry department works to remove invasive plants that can choke out trees. “We have, obviously, bittersweet, Japanese knotweed, multiflora rose; there’s devil’s walkingstick in Elizabeth Park,” Dionne said. “We have garlic mustard. Essentially, they just take off and take over areas where trees and native vegetation could be thriving.”

Another invasive is Japanese barberry. “When you have barberry, you have an increase in tick population. It’s not fun,” Dionne said.

In Bushnell Park there were two “scions” — genetic descendants — of the historic Charter Oak, which toppled in 1856 in a storm. 

“We had to unfortunately remove one of them because of the amount of decay that was in the trunk,” Dionne said.

“So I’ve been working with a nursery here in Connecticut, Planters’ Choice, for … six or seven years now. And they’ve been taking cuttings from our site and growing new ones. So in the next couple years, I’m hoping we can start planting a couple of new ones in Bushnell Park,” she said.

One project, led by the U.S. Forest Service, has brought 150 oaks to 10 plots in New Haven to test how different species will thrive in a more northern climate, according to Chris Ozyck, associate director of the Urban Resources Institute.

“The idea is that these oaks were collected all up and down the East Coast and grown down in Tennessee, and then each city has a cohort of oaks from different parts of the East Coast that is their genetic makeup,” Ozyck said.

The project is called assisted migration, “where you’re helping forests move more quickly, so that the species that rely upon them are not so vulnerable” to climate change, he said.

Chris Martin, Connecticut’s state forester with the Department of Energy and Environmental Protection, said the dry conditions can alter the ecology of the forest. One example is the spongy moth (once called the gypsy moth), introduced in Massachusetts in the early 1900s.

Spongy moths feed on tree leaves, defoliating the trees.

“In the late 1980s, there was a fungus in the soil that is activated when wet, and it kills the spongy moth caterpillars before they pupate, before they become a moth,” Martin said.

But in 2016-17, drought arrived in eastern Connecticut. “We had this episodic drought in the spring; the soils stayed dry; the fungus never emerged,” he said. “And the caterpillars thrived, pupated, became moths. And then the moths lay the eggs later in the summer, so you had several years of consecutive spring drought and the population just blossomed.”

The outbreak ended in eastern Connecticut in 2018-19, but now it’s in upper Litchfield County, Martin said. As the drought wanes, things should return to normal, he said.

“The natural ecological weather pattern systems have normalized and created somewhat of an equal playing field for both caterpillar and fungus,” he said. “But you throw the weather off kilter and then the whole system doesn’t function the way it should.”

The age of Connecticut’s forests makes the spongy moth more dangerous, Martin said. “They’re naturally aging out, so they become more susceptible and more vulnerable to stressors,” he said.

“One year of defoliation, maybe two years of defoliation consecutive would, in the past, in the 1980s, certainly curb growth,” Martin said. “You might have some mortality, but what we saw most recently with the older oak trees now being attacked in the 21st century, they’re succumbing after the second year of defoliation.”

The white oak has the hardest time rebounding, even though trees will put out a second set of leaves in the summer. “They’re utilizing two growing seasons of energy in one growing season, and so it really stresses them out and puts them in a weakened state where they need to recover,” he said.

The loss of oaks affects wildlife too, Martin said.

“Oak trees, with their mass production of acorns, is one of our most valuable wildlife trees … for larger mammals and turkeys and whatnot, but also for all kinds of insects and butterflies and other types of native species,” he said. “We call it one of our keystone tree species. It’s really critical for southern New England and obviously Connecticut’s functional ecology.”

Connecticut is typed as majority oak-hickory forest by the U.S. Forest Service, “and there’s an associate of trees that are within that definition of forest type, red maple being one of them. But red maple itself is the dominant tree species” in the state, Martin said. “So red maple’s doing very well. Sugar maple is doing better.”

Another tree affected by drought is the white pine, although Martin said it’s doing fairly well. “White pine will show some mortality two or three years later, past the drought. So it’s like a delayed response. So sometimes we do see white pine die back from drought,” Martin said.

A large number of the state’s ash trees have died after being attacked by the emerald ash borer, which arrived about 10 years ago.

“Some of this ties back to our global economy, where we’ve had shipments of different wood products from other parts of the country or even stowaways on cargo ships not associated with packaging material, emerald ash borer being the one that’s kind of run the gamut across Connecticut already,” Martin said.

“It’s causing major headaches for municipal tree budgets and forest landowners and, actually, private free small property ownership,” he said. “You have a dead tree in your yard, or a house or garage or swing set, you’ve got to address it and people have incurred some financial hits because of these dead trees.”

Some ashes manage to survive, and the University of Pennsylvania is studying the “lingering ash” phenomenon, Martin said. Also, the Connecticut Agricultural Experiment Station has been releasing a parasitic wasp “that feeds specifically on these emerald ash borer beetles, and there seems to be some hope there,” he said.

The idea is that as the beetles run out of ashes to feed on — they only attack mature trees — and as the wasps lower their numbers, the ash will come back, he said.

The parasitic beech leaf disease, caused by a wormlike nematode, has been attacking that species, Martin said. Not all beech trees die from the disease, but those that “have some other type of weakness to them, whether overcrowded or old or having some beech bark concerns. If they’re weakened, they’ll definitely succumb.

“It’s scary-looking because beech was almost like the infallible tree. Nothing can touch a beech,” Martin said. “But here we have this nymph that’s curling up the leaves and making them look kind of mottled and odd. I think the jury’s still out on that.”

As the ashes and oaks die off, invasive species tend to thrive, Ozyck said.

“We’re going to open up huge sections of forests to light, and those invasives are going to start taking off and it’s hard for our native trees to really compete,” he said. “So we’ve got this double whammy that’s happening. Globalism brings in these exotic species that prey on our non-defensible natives and that climate is stressing the plants.”

Also in New Haven, the Friends of Edgewood Park Green Team has been removing invasives such as bittersweet, which “were twining around a lot of healthy mature trees and lots of little baby trees,” said Stephanie Fitzgerald.

The group now monitors any new growth of bittersweet. “And we’ve probably planted about 100 trees in the last 10 years,” she said. “In the beginning … we were planting really for aesthetic purposes. And that’s fine.

“And then Chris (Ozyck) has got us interested in trying to plant different kinds of trees. … One of the ones that we’re really having fun with, at least it seems to be doing very, very well, is a bald cypress,” she said.

They’ve planted three of the trees, to go along with one at the edge of the duck pond, which was planted 40 to 50 years ago.

A bright spot in the state’s forests is the federal money coming into the state to improve the tree cover, Martin said.

“The Inflation Reduction Act in particular has potential to bring millions of new dollars into Connecticut to help with our urban forests,” he said. “And that’s one thing that the governor himself has really tuned into, where he wants to see, as well as we do, obviously, a 5% increase in tree canopy cover in the communities that are most vulnerable to heat islands.”

Connecticut is fortunate in having so many species of trees, which show their glory each fall, Martin said.

“Where it really hits home with folks that have traveled a lot in different parts of the country and where there’s only maybe a half a dozen or three or four different tree species on the landscape,” he said.

“In Connecticut, we can have up to 20 different tree species within one acre of land. If any state is poised to thrive in the climate change scenario,  Connecticut is, because we already have a very diverse forest type as far as a lot of different kinds of trees growing here,” he said. “So something is going to thrive and something is going to succumb but we’re going to have trees.” 

Ed Stannard can be reached at estannard@courant.com.