Editor's Column

Guest Columns

Forest Facts

By: Jim Petersen

Across the Northeast, net annual forest growth exceeds harvesting by safe margins, except in Maine spruce-fir forests devastated by the most recent spruce budworm epidemic. (See nearby, “Condition and Outlook for Maine’s Spurce-fir Forests: Aftermath of the Spruce Budworm Eipdemic”). Fig. 12 (pg. 19) illustrates net annual growth and removals of growing stock and sawtimber for Maine and New York counties in the Northern Forest Lands Study Area. Such detailed information is not available for Vermont and New Hampshire because the relatively low intensity of field inventory plots did not provide statistically valuable estimates at the county level.

How Timber Harvesting Affects Migratory Birds

The remarkable recovery of northeastern forests is paralleled by the equally remarkable recovery of many wildlife species that were pushed to the brink of extinction by nineteenth century timber and farming influences. Among this century’s success stories: the return of moose, black bear, white-tailed deer and wild turkeys.

Until recently, much less was known about the recovery of migratory bird populations. Now there is evidence many of them are doing quite well, while others still have some distance to go. Not all bird species use the same kinds of forest habitat, a fact that has a direct bearing on their population numbers. For example, birds that do well in younger, more open forests appear to have no difficulty adapting to timber harvesting, while others that prefer more mature, closed-canopy forests do have trouble adapting to harvest-created habitat changes. How much difficulty these birds are having is hard to gauge, because even species that prefer the seclusion of mature forests sometimes find their food in more open environs.

Black-throated Green Warbler

Some of the most interesting habitat research currently underway in the Northeast is being conducted byDr. John Hagan, Senior Ecologist and Director of ConservationForestry at Manoment in Brunswick, Maine. Manomet (formerly Manomet Observatory) is a non-profit scientific research group. It got its start in the 1960s monitoring migratory bird populations. Since 1992, Dr. Hagan has been studying the effects of industrial forestry on birds and forest structures in Maine. His research is concentrated on lands belonging to S. D. Warren and Great Northern Paper.

“What we can say at this point is that some bird species benefit from harvesting, while others appear to be hindered,” Dr. Hagan said in an April interview. “We also know that clearcutting does not create ‘biological deserts’ as some have suggested.”

Among bird species that benefit from clearcut-related habitat changes: Chestnut-sided Warbler, Common Yellowthroat, American Kestrel, Lincoln’s Sparrow and Mourning Warbler. And among birds that are hindered: Blackpoll Warbler, Black-throated Green Warbler and Blackburnian Warbler.

Most bird species are “site-faithful,” meaning they return year after year to where they were the year before.When they find their previous nesting area has been harvested, they generally move to an adjacent forest. What is not known is how or if harvest related habitat losses impact population numbers. Some birds seem to need no more than an acre of habitat, while other breeding pairs need a hundred acres or more.

"We have some data for southern New England," Dr. Hagan reports. "We know urban-related forest fragmentation  is a big problem for some birds, but annual surveys have only recently been conducted in northern Maine, so in a long-term sense, we don't know how bird numbers are impacted by harvest-related habitat changes."Given the likelihood that reliable harvest impact data  will not be available anytime soon-and to reduce the potential risk of species loss-Dr. Hagan is encouraging the Northeast's large landowners to maintain an ageclass distribution that provides ample mature (80-120 year old) habitat for species that need it.

"Presently, I cannot identify anybird species in Maine that require  old growth forests to maintain a healthy population," Dr. Hagan says. "The challenge is to figure out how to keep a full array of habitat in a working forest. That's not easy to do when you are a paper manufacturer. Paper company forests are definitely trending toward younger age classes."

The trend toward younger maximum forest age has become a focal point in Dr. Hagan's habitat research. With annual harvest rates running at about 1.5 percent, he wonders whether any plant or animal species associated with mature forests will drop out as younger forests become more predominant in northern Maine.

"The forests we see today are the product of an earlier era when the annual harvest rate was less than it is now," he explains. "What this means is that the Maine forest landscape we see today will not look the same in 30 or 40 years. We need to learn how to accommodate a full range of wildlife species in this changing landscape."

But how can such a range of wildlife species be accommodated in forests that are growing younger? Many who voted to ban clearcutting in Maine think such a ban would produce the older forests they believe would most benefit wildlife, but Dr. Hagan is less certain how wildlife would benefit.

Common Yellowthroat

"Selection cutting usually involves harvesting 20 to 30 percent of the timber in a stand every 15 or 20 years," he explains. "The result is a more open-canopy forest with fewer slightly older trees than would naturally be present. But selection harvesting does not mimic the mature, closed-canopy forest nature would offer up across much of Maine's Northern Forest if given the chance. Both techniques-clearcutting and selection harvesting-mimic nature is some ways, but neither technique produces an exact replica of natural disturbance patterns produced by wind, disease, ice or the occasional fire we see in the North woods."

Then there is the acreage factor: given the demand for-say-a billion board feet of wood fiber annually, it takes many more partial cut acres to meet demand than it does clearcut acres. Is it better to disturb fewer acres more intensively every 60 to 70 years, or is it better to enter a stand less aggressively every 15 or 20 years? Which alternative produces the better overall outcome for wildlife? Dr. Hagan concedes he does not know. But the Maine Forest Service has come up with some interesting numbers worth considering. Between 1989 and 1994, clearcutting decreased from 45 to 11 percent of annual harvest acres. At the same time, the number of partial cuts increased from 55 to 89 percent-and the number of total acres harvested by clearcut and partial cut increased from 326,000 to 504,000 acres.

To help mitigate the immediate impacts of harvesting, Dr. Hagan offers a suggestion that seems certain to raise the eyebrows of a public obsessed with orderliness in forests: leave more snags and woody debris-branches and treetops-in harvested areas. Such debris holds moisture, enriches the soil and provides hiding and nesting cover for birds, small mammals and amphibians.

"Leaving woody debris may seem to add to the eyesore clearcuts create," Dr. Hagan explains, "but logging residue is very helpful where wildlife is concerned. Policymakers need to accept the fact that many of the things that benefit wildlife don't fit well within the public's perception of what constitutes good forest stewardship."

Where the future is concerned, Dr. Hagan is both a pragmatist and an optimist. "About all we can do is learn as we go," he says. "We need to be flexible and open to new knowledge. Where wildlife is concerned, we will never have perfect knowledge, and we will never know all there is to know."

Editor’s note: To learn more about Dr. Hagan’s views concerning timber harvesting and wildlife habitat, read “Clearcutting in Maine: Would somebody please ask the right question?” Maine Policy Review, July 1996, or write Dr. John Hagan, Manomet, 14 Maine St., Suite 404, Brunswick, Maine, 04011.

"We must always consider the environment and people together, as though they are one, because the
human need to use natural resources is fundamental to our continued presence on earth."