What’s best for the trees?

Asheville’s drinking-water watersheds have been in the spotlight recently as City Council has considered developing a forest-management plan for these protected water sources. But amid all the heated discussion, one topic has been conspicuously absent: What type of activity or inactivity would best serve the forest itself?

Over the past 60 years or so, our region’s forests have been steadily assaulted by a succession of introduced insects and pathogens. The American chestnut has been eliminated as an overstory tree, and virtually every white walnut has been expunged from the Southern Appalachians. Flowering dogwood now occupies less than half of its native range. The American beech has been dislodged from forests over 4,500 feet. And now, hemlocks are under attack by a small, exotic insect known as the hemlock woolly adelgid. Bit by bit, our forests continue to be degraded.

Much as we might wish for the assault to halt or at least ease up, the truth is that expanded global trade increases the number of pathogens and insects invading our forests. The gypsy moth, sudden oak death and the emerald ash borer have all become entrenched in large sections of this country, and there’s a high probability that one or more of these pests will be established in our region within the next 20 years.

This insidious degradation of our forests will inevitably degrade water quality in Asheville’s watersheds. Consider the case of the hemlock woolly adelgid. Most hemlocks grow along clear mountain streams, where their shade helps moderate water temperature. When hemlocks die, there’s a greater fluctuation in water temperature, which can affect the survival and dynamics of microorganisms as well as aquatic plants and insects. It will probably impact the decomposition of organic material in the water as well. The extent to which the loss of hemlocks affects water quality will depend on which tree species replaces them and whether it’s native or exotic.

International trade agreements and port-of-entry regulations are needed to prevent the introduction of exotic pests. But active forest management can mitigate the harm that exotic plants, insects and pathogens do to our forests. And in Asheville’s drinking-water watersheds, this can be accomplished without exploitive commercial logging, clear-cutting or extensive daylighting.

Active management does mean maintaining existing roads in a non-erodible state, closing obsolete roads, reducing and restricting the presence of exotic plants, and yes — it does mean cutting trees. But trees should be selectively cut to promote improved stand structure and the growth of genetically superior trees. And the cost of forest management should not be borne by taxpayers; it should be covered by the revenue from harvested trees. Conversely, however, that revenue should be used to benefit the forests that generated it — not tapped to fund water-system needs.

Can active management be accomplished in an ecologically benign fashion? Yes. Many municipal watersheds throughout the United States are actively managed. In fact, Asheville residents supplied by the South Mills River Pumping Station are already using water that comes from an actively managed forest.

Active management of the watersheds may or may not restore the American chestnut to the forests over the next 10 years; it may or may not preserve at least a remnant of the region’s hemlock trees. But doing nothing is neglectful, if not an outright betrayal of our responsibility to nurture the watersheds’ forests.

[Monty Wooten, a registered N.C. forester and certified arborist, serves on the Asheville Tree Commission.]