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How much old-growth is left?

In February 1991, the U.S. Forest Service and the Wilderness Society each released inventories and maps of the remaining old-growth forests in the Pacific Northwest and northern California. These inventories were long-awaited because they promised to provide basic information for resolving the old-growth controversy: How much old-growth remains? Where is it? How much is threatened by timber harvesting?

The results, however, were startling in their contrast. Although the Forest Service and Wilderness Society based their inventories on the same definition of ecological old-growth and used similar high-tech geographic information systems for analysis and mapping, their estimates of old-growth differed significantly. This left many policymakers in a quandary, wondering why the estimates vary so much and which information to use in attempting to settle the old-growth dispute.

The basic old-growth definition used in both surveys was developed by a task group in 1986 at the Forest Service's Pacific Northwest Research Station. The definition has come to be known as "PNW-447" after the publication number in which the definition is presented, and essentially it is the ecological definition of old-growth forests in the Douglas-fir region. The definition contains various criteria for determining whether a forest qualifies as ecological old-growth: It must have a given number of large trees per acre, a certain amount of crown closure, a multilayered canopy, a number of dead standing trees or snags, and down logs.

According to Forest Service fact sheets, the criteria that the agency used in its old-growth inventory came as close to PNW-447 as possible, but did not include snags or down logs since these are not detectable from the air.

The Wilderness Society inventory gave estimates of both "ancient forest," which contains some but not all of the old-growth characteristics identified in PNW-447, and "old-growth," which has a high probability of meeting all the criteria of PNW-447, including snags and down logs.

The Forest Service inventory found 4.3 million acres of old-growth remaining in 13 national forests (about one-fourth of the total acreage in those forests). The Wilderness Society inventory found 3.8 million acres of "ancient forest" remaining on 12 national forests-one fewer than the Forest Service surveyed. This half-million-acre discrepancy seems reasonable given the difference in number of national forests, the magnitude of the survey, and the potential for variation in definitions and survey methods.

However, based on more detailed surveys of four national forests and previous inventories of the other eight, the Wilderness Society estimated that "old-growth" accounts for only two million acres of the ancient forest. This estimate--less than half of the Forest Service old-growth estimate-created discrepancy that is much more difficult to understand.

To gain some insight into the differing results, we compared the Forest Service and Wilderness Society estimates of remaining old-growth on the four national forests for which the Wilderness Society had done more detailed assessments--the Mt. Hood, Mt. Baker--Snoqualmie, Olympic, and Gifford Pinchot. Although the Forest Service estimated 1.7 million acres of old-growth in these forests, the Wilderness Society reported only 650,000 acres. Thus the results--in the national forests where the surveys can be most readily compared--show a significant variation. It appears that there are indeed substantial differences in the manner in which the Forest Service and Wilderness Society applied the PNW-447 definition in their respective surveys.

How much of the remaining old-growth is threatened by timber harvesting? The Forest Service inventory shows that 966,000 acres are protected in wilderness areas; another 1.4 million acres are protected under various designations in current national forest plans-at least for the duration of those plans; an additional 646,000 acres would be protected as Habitat Conservation Areas (HCAs) under the strategy proposed by the Interagency Scientific Committee to conserve the spotted owl--if the agency adopts this strategy. Thus, the Forest Service estimates that nearly 3 million acres (68 percent) of the remaining old-growth would be protected with the HCAs, though 1.4 million acres (31 percent) would be available for timber harvesting.

The Wilderness Society inventory shows that 934,600 acres of the remaining ancient forest are permanently protected in congressionally designated wilderness, special areas, and Research Natural Areas (RNAs); an additional 1,088,500 acres would be protected if the HCAs were adopted. Thus, the Wilderness Society estimates that more than 2 million acres (54 percent) of the remaining ancient forest would be protected with the HCAs.

Although the Forest Service and Wilderness Society acreages differ, the estimates of the percentage of old-growth currently protected is quite similar. Basically, both indicate that more than half of the remaining old-growth would be protected from timber harvesting if the HCAs were adopted.

The difference between the Forest Service estimate of 68 percent protected and the Wilderness Society estimate of 54 percent is accounted for by the fact that the Wilderness Society does not consider lands classified as unavailable for timber harvesting under current national forest plans to be protected.

An expectation that the Forest Service and Wilderness Society might come up with similar estimates of the remaining old-growth forests in the Pacific Northwest was probably too optimistic. Despite the fact that they used the same definition and survey techniques, the inventories still required a great deal of subjective judgment and interpretation. The task of inventorying forests, which appears at first to be highly scientific and objective, is actually an art as well as a science, especially when definitions and inventory methods are in their formative stages.

Policymakers who were hoping for some consensus on how much old-growth remains may be disappointed. Unless the inventories are reconciled, these policymakers will have to choose between them, and the decision for many will be largely a political one.

Despite the discrepancy, the inventories still provide much better information about the remaining ecological old-growth than was available a year ago when the old-growth debate began to heat up in Congress. At that time, the Forest Service still had to rely on previous inventories in which old-growth, in simple terms, meant forests with old trees, not necessarily with the other characteristics of ecological old-growth forests. That is why Forest Service estimates at that time were much higher-more than six million acres in the PNW national forests.

Although the new inventories provide different figures for how much old-growth remains and how much more needs to be protected, the Forest Service and Wilderness Society have narrowed the debate, promoted better understanding of what constitutes ecological old-growth, and generated maps policymakers can use to better comprehend the situation.
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Title Annotation:forests
Author:Eng, Anita
Publication:American Forests
Date:Sep 1, 1991
Words:1077
Previous Article:"Destructive recreation" on our public forests.
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