2010-01-21 / Community News

Importance of Snags

Most everyone understands the benefits that living trees provide for wildlife, however, not many people understand the value of dead trees. Dead trees (or “snags”) are created by a variety of natural processes such as wind, fire, flooding, drought, disease and old age. Snags can also be created unnaturally by man as a result of over watering, construction damage to root zones, root suffocation, herbicide application, etc. Usually people want to remove snags as soon as possible. We seem to think that once a tree dies it is no longer useful and should therefore be removed, however that is not the case. Snags are extremely valuable to the forest ecosystem.

Many wildlife species rely heavily on snags for their survival. While some woodpeckers nest in cavities excavated in living trees, many of them nest only in cavities excavated in snags. Without snags, these woodpeckers can’t exist. Once cavities are abandoned by woodpeckers, secondary cavity-nesters move in such as chickadees, titmice, wrens, and bluebirds. In addition to excavated cavities, the often hollow trunks and limbs of snags provide excellent homes for owls, raccoons, squirrels and certain species of bats.

There are often situations that require human action to maximize the usefulness of snags while minimizing any drawbacks. If a snag is located where it would pose no danger to people or structures if it should fall, then it could be left alone without serious drawbacks. However, if a snag is located near a structure, driveway, or walkway, steps should be taken to reduce the risk of injury to people or property. The height of the tree determines the radius that could be affected should any part of the tree fall. For example, if a 30-ft tree falls, then anything within a 30-ft radius could be affected. To reduce the risk of damage, you can “limb” the tree or remove the major limbs leaving only the main trunk standing. You may also consider “topping” the snag or removing just enough of the top so that it doesn’t extend beyond

the height of surrounding trees. (Topping should be done by a professional.) Both of these techniques will reduce wind stress on the snag, thus allowing it to stand longer.

Because snags are extremely valuable for

many wildlife species, it is

often recommended that they are “created” if none exist in the area. To create snags, carefully select a tree and “girdle” it. To girdle a tree, you simply cut a ring into the base of the tree that is about an inch deep and an inch wide at the bark. Since it is only the outer rim of the tree that is alive and transporting nutrients, cutting this section will kill the standing portion of the tree. Depending on the species, the roots may or may not remain alive and re-sprout. When selecting a tree to girdle, consider those that are not native to the area, are short-lived, or are undesirable for some other reason. Remember to also consider the tree’s proximity to structures, driveways, etc. before girdling it.

Finally, it is important to help others understand the value of snags. Educating others will not only help them understand why snags are needed by wildlife, but will also help them understand the actions of those who are employing these management practices.

If you would like to contact your local biologist, see our website at; http://www.tpwd.state.tx.us/ wildlifebiologist.

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