Snag Trees and Healthy Ecosystems

“Dead” trees are actually full of life

What are the ecological benefits of snags? Standing dead trees, called snags, provide birds and mammals with shelter to raise young and raptors with unobstructed vantage points.

Snag trees can be beautiful. They also provide vital habitat for birds and wildlife. Photo: Kelly Smith / United by Blue

As forest ecologist Jerry Franklin, likes to say: “A dead tree is more alive than a live tree.” Alive with critters from large to small, that is!

Hundreds of native birds, mammals, amphibians, reptiles, and nearly all fish – because of the beneficial effect of snags on watersheds – benefit from snags for food, nesting, or shelter.

Snags are homes

Only 30 bird species are capable of making their own nest cavities in trees. The pileated woodpecker is a famous example. Another 80 animal species – like fishers – depend upon previously excavated or natural tree holes for their nests. Some, like wolverines, count on deep drifts piled around natural obstructions like dead tree trunks to dig their deep dens in winter.

The insulation of a tree trunk home allows wildlife to survive high summer and low winter temperature extremes. Tree cavities and loose bark are used by many animals to store their food supplies, while insects living in dead wood eat thousands of forest pests which can harm living trees. Woodpeckers and creepers feast on the wood-eating insects and provide “sawdust” for ants to process. Deer and mountain caribou eat the lichen growing on the trunks.

When they eventually fall into or near water and wetlands, fish and amphibians hide under and around dead wood. This aquatic “structure” provides important shelter for juvenile salmon, steelhead, char and trout. Without woody debris in our rivers and streams, these watersheds can’t provide adequate habitat for many native fish species.

Whether created through natural processes or active forest restoration, standing and down dead wood play an important role on the landscape. Learn more about the debate around snag trees in this article from Yale Environment 360!

Respecting human needs while preserving habitat

We are working with partners to increase awareness of the importance of snags, and ensure that forest management policies on our public lands protect the values they offer. Three national forests in Washington – the Okanogan-Wenatchee, Umatilla and Colville National Forests (click here to see a map of acreage open to snag felling in Washington) – currently allow the felling of snags on portions of their lands for firewood unless there are active cavity nests in the tree.

A snag tree preserved for wildlife habitat in the Central Cascades. Photo: Chase Gunnell

Firewood cutting and snag felling is also already restricted in wilderness and some sensitive areas. A firewood gathering guide from Okanogan-Wenatchee National Forest can be found here. The Okanogan-Wenatchee and other national forests also provide special firewood collection zones. Often these are small trees left behind or piled up after forest thinning and stand reduction projects.

However, from the ground it can be extremely difficult for woodcutters to determine if a snag or dead tree is being used for nesting or denning. Sensible firewood gathering regulations are needed to protect nesting and denning sites.

Due to the policies mentioned above and a lack of enforcement capacity, researchers have documented not only the continued loss of snags on the landscape but the removal of trees providing home to wildlife such as the black-backed woodpecker, white-headed woodpecker, Pileated woodpecker, Lewis’ woodpecker, and American three-toed woodpecker.

We understand that firewood gathering is an important activity for campers and those living in rural areas, but it’s important to leave big snags standing and when possible, to gather downed dead wood from the forest floor!  

While there is important social and economic value to firewood gathering and recreation on these national forests (and often some ecological benefit from the removal of small and downed dead fuels), the removal of standing dead wood needs sensible and scientifically-sound management guidelines to help protect nesting sites, wildlife habitat and healthy ecosystems.

Learn more about snags