Jason and Aga Jones loved the magnificent oak tree that was once the centerpiece of their backyard. In 2013 — a year after they bought their home in Takoma Park, Md. — they restored a circular stone retaining wall around the base of the tree. In 2019, they added an extension to the back of the home with enormous windows from which they could admire the majestic branches and watch squirrels build nests and collect acorns.

Then late last summer, when they hired a company to lop off branches encroaching on the neighbor’s yard, the company’s workers pointed out ominous symptoms: browning leaves, dead branches. Within a year, the tree was dead.

“It’s sad. We bought the house because of this oak tree. It’s a great old tree,” Jason Jones said, shaking his head as he peered up at the brown leaves clinging to lifeless limbs on the last evening before workers came to cut it down.

He fetched a tape measure from his basement to take stock of the tree: 12 feet in circumference, 4 feet in diameter. “A couple of arborists told me that it is probably one of the oldest trees in the state, but unfortunately it has the blight and it has to come down,” he said, looking across his neighborhood’s sweeping green canopy, then back at his own withered oak.

Oak trees are dying across the Mid-Atlantic region, crippled by extreme weather, old age, construction and development, then finally succumbing to disease and pests. Experts say the oak decline was triggered by the year of record rainfall that waterlogged the Washington region from 2018 to 2019, immediately followed by a flash drought in the hot, dry summer of 2019.

“The anaerobic conditions of flooded soil are not good for oaks,” said Karen Rane, director of the Plant Diagnostic Laboratory at the University of Maryland, noting that many of the hard-hit oaks are next to highway construction, where there are changes in drainage and soil compaction.

“They lose oxygen in the soil. That’s stress on older trees — or on any tree, but older ones can’t tolerate it the way younger trees can. That may have triggered an acceleration of decline in these older trees,” Rane said. “Once the trees weaken, trees emit signals that allow opportunistic insects to find them and attack. That’s the last straw that breaks the camel’s back.”

The oak decline has affected the D.C. region and states including Pennsylvania, Virginia, Maryland, Delaware, West Virginia and New Jersey, experts said. Symptoms are early browning of leaves, thinning canopy cover and loss of branches, Dorothy Borowy, an ecologist and coordinator of integrated pest management for the National Park Service’s D.C. region, wrote in an article last year.

Anne Arundel County in Maryland has even set up a web page where residents can report sick or dying trees.

The resulting tree loss has been most evident in communities with older trees, such as Takoma Park, where residents fret as the roar of chain saws and mulching machines portends the loss of another big shade tree.

Takoma Park, a D.C. suburb known as a liberal enclave, has strict provisions to protect its trees. A permit is required for the removal of any tree, living or dead, with a trunk more than two feet in circumference, and for any construction, excavation or pruning that would remove more than 10 percent of the “live canopy.”

Marty Frye, the city’s urban forest manager, said that in the years he has worked for Takoma Park, more than half of the tree removal permits he has reviewed have been for oak trees. He started his current job in October 2020 but began working on the city’s tree removal permits about three years ago — which is when, he said colleagues and property owners told him, the uptick in oak tree deaths began.

Rane, who has traveled throughout the region to observe the oak tree situation, said of Takoma Park, “There happen to be a lot of over-mature trees in that town.”

Her U-Md. colleague Dave Clement, a plant pathologist who joined her for a video interview with The Washington Post, estimated that most of the dying trees in the region are between 80 and 120 years old.

Rane added: “People think oaks live to 300 years, but not in an urban environment. There’s just too much going on.”

At the Jones home, Jason Jones picked up pieces of bark the tree had shed to reveal little piles of sawdust at the base of the tree. These piles, Frye said, are a “telltale sign” of pests such as Ambrosia beetles, which attack after a tree signals its weakness.

Some trees die slowly, losing branches over many years, Frye said. But others, such as the Jones family’s tree, die suddenly.

“That’s a more disconcerting, shocking sight,” Frye said. “It seemed to leaf out pretty well, then it browned out kind of early. It is consistent with the Ambrosia beetle putting the nail in the coffin.”

The early symptoms of a sick tree are subtle: a thinner canopy, reduced leaf size and new twigs that are about half the usual length, Clement said. “People don’t notice leaf size, how thin a canopy looks, if you see light through the canopy — those are subtle indications that things are on a less-than-normal path.”

Then the symptoms shift toward the sawdust from beetles attacking the trunk, he said. “You start to see these organisms, and people ask, ‘What can I do?’ Well, it’s way too late for remedial action.”

The dying oaks are suffering from numerous blows — and conditions caused by humans can exacerbate the problem, experts say.

During the video interview, when Rane and Clement saw a photo of the retaining wall around the base of the tree, they both emitted knowing gasps. “That retaining wall around the tree didn’t help if it went up in the past 10 years,” Clement said. “If that tree had been a 25-year-old tree, it probably wouldn’t have struggled or had that much of an effect. But an older tree, if you start to do stuff around that, any root disturbance, they’re a lot more sensitive. It’s harder for them to recover.”

“Some of these yard trees die from TLC,” Rane added.

Aga Jones said a flimsy stack of bricks had encircled the tree when they bought the house. The Joneses fortified it and built it up shortly after moving in.

Experts say retaining walls, construction near the tree or even piling up soil can deprive the roots of oxygen, and the bigger a wall, the worse it can be for the tree. The builders did warn the Joneses that they couldn’t build the wall too high because it would stress the tree, Jason Jones said, adding, “That was something we thought about when we built the wall, but we thought it was a calculated risk.”

On Oct. 20, the Joneses had the large branches cut off but kept the bulk of the trunk, thinking they would build a treehouse for their children. But the dead trunk was too sad a sight — a reminder of what they had lost. They will leave it for now for the woodpeckers to feast on but plan to have it cut to a smaller stump in the spring, Aga Jones said.

Homeowners throughout the region have sought answers from experts about how to save their trees. Clement said remedial soil work might help sick trees recover — alleviating soil compaction with an air spade or breaking up the surface layers of the soil. He advised people to keep things away from the trunks — retaining walls, other plants or even more soil — and to avoid running the lawn mower over the surface of the roots. Mulching can help, Rane said, but she added, “If we keep getting extreme weather events ... we’ll continue to see these events.”

Most important, Clement said, is a tree replacement strategy — a 25-to-30-year cycle of adding, removing and replacing trees.

“When a big tree comes down, plant with another big tree — not with a short-lived tree” such as a crepe myrtle, dogwood or redbud, Clement said. “I would encourage people to keep planting more shade trees. Stagger their planting, space out the plantings. If you have a small yard, a single large tree is all you really have room for.”

The Joneses are planning to plant another tree behind the spot where the oak was located. Jason Jones worries the oak’s decomposing roots could cause his yard to buckle and become uneven. Clement said that shouldn’t be a concern and suggested looking at the bright side: “He may see mushrooms pop up. He’ll have an increase in insect soil microorganisms, all kinds of good stuff happening.”

For now, the death of their oak tree means a lot less yard work: Jason Jones said he had to rake a half-dozen times each fall and clean up “tons of acorns.” But he already misses the squirrels that feasted on the nuts and nested in the tree: “This used to be Grand Central for them.”