Picture yourself walking through a deep, dark coniferous forest just before nightfall. Trees tower overhead, their branches draped with lichen. Moss covers toppled trunks. An owl calls in the distance, a twig snaps somewhere nearby, and the faint sound of paws skittering across the forest floor sends a chill down your spine. You start to get the feeling you’re not alone.
Mature and old-growth forests replete with large, old trees, snags, and logs aren’t just magical places filled with creepy creatures and forest friends alike. Older forests play an important role in the cycling of water. They also absorb and store huge amounts of carbon that help mitigate impacts from climate change. It’s no surprise that wildlife loves them, too. These forests can host many species – often in greater numbers than other forest types – in part because tall trees with thick, furrowed bark, multi-layered canopies, and an abundance of fallen logs and leaf litter create more niches for organisms to live in close proximity.
As trees age, damage from insects, diseases, and windstorms creates cavities. Creatures of all types use these hideaways to evade predators, seek shelter from rain or snow, or build nests to raise their young. Standing dead trees, or snags, also provide valuable habitat for cavity-nesting birds, mammals, and insects.
Older forests can also provide key habitat for species that feed on dead or decaying materials (known as “detritivores” and “saprotrophs”). These can include arthropods, fungi, and mollusks. (That’s right – mollusks live in forests, too: this group of organisms includes terrestrial snails and slugs!)
To some, snags and fallen logs might seem like “waste,” but we know that many species rely on these forest features. Increasingly, foresters and land managers will intentionally leave behind large snags or downed trees to provide habitat and to encourage other species – including seed-dispersing birds and mammals – to visit areas after timber harvest or extreme forest fires.
The U.S. Forest Service is currently considering a framework to ensure that mature and old-growth forests can survive and thrive even in the midst of our changing climate. That’s important not only for these forest creatures but for all of us humans who depend on the clean air, water, and climate benefits that forests provide.
Some of the organisms that live under logs or hide in holes in trees are misunderstood. Click on the photos below to learn more about six species who thrive in mature and old-growth forests across the country – and learn why they’re our friends, not foes. Each of them plays an important role in their ecosystem.