Snags, stumps, and logs provide habitat

Three birds perched on a snag. A ball moss
(Tillandsia recurvata) also lives on this snag.

Dead standing trees are snags. If a snag is located so that it will not hurt people or damage property, leave it standing for its wildlife value. Snags are highly productive sources of habitat that work well in both natural areas and designed landscapes.

Tree basics

The vast majority of organisms on our planet depend upon the life-giving process of photosynthesis. Plants and other organisms with chlorophyll combine carbon dioxide from the air and water with energy from the sun to form sugars and oxygen gas. The plant can then combine the sugars to form starches, fats, enzymes, or whatever the plant needs. 

Photosynthesis: 6CO2 + 6H2O >> C6H12O6 + 6O2

Then most living organisms (plants, animals, fungi, bacteria) take in oxygen and digest the sugars in one form or another to gain energy for life through respiration, a process the equal and opposite of photosynthesis. 

Respiration: C6H12O6 + 6O2  >> 6CO2 + 6H2O 

Since trees normally live for many years, they sequester carbon in their wood and root tissues as long as they live, while the flowers, fruits and leaves store carbon only temporarily until they are eaten or decompose. Much of this decomposing plant matter ends up in the soil. But when a tree dies, the wood begins to break down as bacteria, fungi, insects, and other organisms begin to absorb the wood tissue so they can gain energy for life. As the wood deteriorates, then birds and other larger animals can consume the decomposers and so the carbon-based sugars stored in the wood moves up the food chain. The organisms store the sugars created during photosynthesis, but as they respire and when they die, the carbon is released into the atmosphere.

One note here on carbon sequestration: The soil sequesters 3 to 4 times as much carbon as all the terrestrial plants, including rain forests. Peat is especially important since it can sequester carbon for thousands of years. This is important because the more carbon sequestered means less carbon dioxide, our most abundant greenhouse gas, in the atmosphere and that is good for our only planet. (Read my article on peat moss.)

After a tree dies, fungi and other decomposers
begin to break down and digest the wood.
 

Snags as habitat

As trees die, they become habitat for many species of insects, fungi, lichens, and mosses. These, in turn, serve as food for animals further up the food chain that eat them. For example, the outer surface of the bark is where small birds such as Nuthatches eat bark beetles, spiders, and ants. The inner bark is where woodpeckers, other large birds, and mammals such as raccoons and black bear eat protein-rich larvae and pupae of insects. This source of insect food is particularly important in winter when insects are harder to find.

The holes woodpeckers make vary in size. Some will naturally enlarge due to the opening rotting thus providing habitat for an even greater number of species. In North America, more than 50 bird species nest in cavities. Eastern Bluebirds, American Kestrels, Wood Ducks, and some species of owls rely on cavities in dead wood for successful reproduction.

Hollow snags and large knot-holes are used by many species of mammals such as squirrels, porcupine, and raccoons. Bats nest and reproduce in the spaces under the bark where it is peeling off the tree. Amphibians, reptiles, and invertebrates seek refuge in natural cavities and dens.

Stumps, snags and logs are important elements in bird-friendly landscapes. Illustration from "The Art of Maintaining a Florida Native Landscape"

Leave dead trees as snags only in areas where they will do minimal damage when they fall.

Stumps and logs

Instead of leaving logs on the curb for yard waste collection, use them as path liners or as a foundation for a stick pile. This helps create habitat in your landscape.

Instead of grinding a stump away, after a tree came down in our back yard during a hurricane, we covered it with pond muck and compost to build a pollinator garden. Years later, we expanded the bed and planted blueberries.

Leaving snags standing is best for habitat values, but where trees are downed for one reason or another, keeping them in your landscape also adds to the habitat and slows down the decomposition so the carbon is sequestered for a bit longer.

If you are left with a stump, incorporating it into the landscaping one way or another is best for creating habitat. The stump shown above that we buried became part of the soil and it was totally gone by the time I planted the blueberries.

We humans are not the only beings on our planet and we can work to better support our fellow inhabitants.Snags, stumps, and logs can play an important role in creating more habitat.

Green Gardening Matters,
Ginny Stibolt

More references

- Habitat gardening
- The value of trees
- Transpiration: Forests' most important service
- Invite birds to your yard
- 6 easy steps to support wildlife