On a late-fall walk through a Barrington backyard or along a quiet trail, it’s easy to pass a dead tree without a second glance—dark trunk, broken branches, a few hollowed scars. But that snag may be one of the liveliest pieces of the landscape. “It’s almost like an apartment building for wildlife,” said Spencer Campbell, Plant Clinic manager at The Morton Arboretum.
A different kind of housing
Holes in trees, known as cavities, form when branches crack, storms scar a trunk, or fungi soften wood that animals can excavate and expand, The Morton Arboretum explains. Once a tree dies, weather and decay create even more ready-made rooms for tenants ranging from bats and owls to bluebirds and squirrels, according to The Morton Arboretum.
The housing market in a cavity can be a chain of handoffs. Woodpeckers are the neighborhood’s master carpenters—primary cavity excavators that drill into soft spots to nest—while other species move in later as secondary cavity users, as summarized by Wikipedia. In yards and woodlots alike, that succession means one hole can host multiple species over many seasons. “The mammals are opportunists,” said Lyn Myers, lead education program guide at The Morton Arboretum. “They take advantage of a cavity that’s already there.”
Not every resident needs a full-on doorway. Deep, craggy bark can shelter overwintering insects and even small bats tucked under sun-warmed bark on the south side of a trunk, according to The Morton Arboretum. “It’s amazing how small they are when they’re folded up,” Myers said.
Cavities can also benefit living trees. When insect-eating birds and mammals concentrate their foraging around a cavity, they can reduce the larvae and wood-borers that might otherwise harm the tree. “If woodpeckers and other animals have a cavity to live in, they may be helping it by eating the insect larvae that would be eating the wood,” Myers said in guidance shared by The Morton Arboretum.
What falls back to the soil
A dead tree doesn’t stop working for the neighborhood. As it breaks down, “it keeps giving back in a different way,” Campbell said. Fungi, insects, and microbes slowly feed on the wood, returning nutrients to the soil and improving its structure and moisture-holding capacity—processes that help new plants take root, according to U.S. Fish and Wildlife Service. Downed logs and standing snags also store carbon that would otherwise return more quickly to the atmosphere, the agency notes.
That is why natural-area managers often keep non-hazardous dead trees in place. The Arboretum notes that where there’s no risk to people or property, leaving snags standing supports birds, mammals, insects, and fungi that depend on them for nesting, roosting, and foraging, according to The Morton Arboretum. “A dead tree that isn’t at risk of falling on people or property can actually be more valuable left standing,” Campbell said.
When to call an arborist
Of course, not every dead or cavity-bearing tree belongs next to a driveway or playground. Urban forestry is a balancing act: communities aim to keep the ecological payoffs of snags while protecting public safety through regular assessments and targeted removals, according to National Geographic. Homeowners face the same trade-off on their lots.
“If you see cavities in a tree in your yard, you should have it inspected by a certified arborist to determine whether it poses any risk,” Campbell said. “Sometimes, a decayed branch or tree may need to be removed.” But he also emphasized that not every hole is a hazard; many living trees can safely host cavities without compromising their structure, according to The Morton Arboretum.
When a professional deems a cavity-bearing tree stable and out of harm’s way, keeping it can be a quiet act of conservation. Woodpeckers—iconic primary excavators—create many of the spaces that secondary cavity users need, a dynamic that links one tree to the well-being of a whole community of wildlife, as outlined by Wikipedia. Meanwhile, the gradual return of wood to soil enriches the ground beneath our feet and helps hold moisture after rains, strengthening the yard’s living foundation, according to U.S. Fish and Wildlife Service.
So the next time a jagged silhouette rises at the back of a Barrington lot or along the edge of a preserve, pause before deciding it’s just an eyesore. There may be more neighbors than you think inside that bark and branchwork. And if you’re unsure about the safety of a particular tree, start with an expert assessment—then, where it’s safe, let that “apartment building for wildlife” keep doing what it does best, as The Morton Arboretum and National Geographic advise.
