Assessing forest ecosystem health in the Inland West - includes related article - Lookout

American Forests, March-April, 1994 by R. Neil Sampson, David L. Adams, Stanley Hamilton, Stephen P. Mealey, Robert Steele, Dave Van De Graaf

Forest health is a condition of ecosystems that sustains their complexity while providing for human needs. Millions of western acres fail to qualify.

In many forested areas of the inland western United States, trees across large landscapes are dying faster than they are growing or being replaced. In other areas, conditions exist that virtually guarantee an onset of serious forest health problems, which may lead to large wildfires, reburning, erosion, and loss of habitat and property. In those areas, it is not just trees and their values that are at risk. Where terrestrial ecosystems are adversely impacted, the entire range of aquatic resources, wildlife, and other values are affected as well. The current conditions, many of which are unprecedented in recent times, demand urgent response. Forest managers on both public and private lands, even though they manage for a different combination of objectives, face a common forest health challenge when the forests in their care are deteriorating.

Within this region, there are also forest areas that, either through management efforts or natural controls, represent examples of healthy, thriving forest ecosystems. In both the healthy and unhealthy areas, managers are challenged to design forest health strategies that focus on: a) the prevention of socially undesirable forest conditions by protecting the forest from insects, diseases, and fire in an ecological framework and b) the restoration of socially desired forest conditions on those areas where it is needed. Management needs to reflect a strong commitment to retain healthy conditions for many values, as well as to study current variability in ecosystem conditions.

Forest health is defined in this context as a condition of forest ecosystems that sustains their complexity while providing for human needs, and it is clear that many of the forests in the Inland West fail the test. In areas where insects, disease, and wildfire are causing total or near-total tree mortality, the evidence of forest health problems is visual and stark. In other areas, visual evidence and widespread mortality may be lacking, but the onset of major ecosystem setbacks are assured by the existence of conditions that inevitably lead to large, stand-replacing wildfires. Managers are challenged to take rapid preventive action to restore these forests to conditions more similar to their historical range of variability, or, where that is judged not possible or desirable, to strive for another sustainable condition.

Without the application of needed silvicultural treatments within a fairly short time (15-30 years), there is great danger that over the next century this region's forest legacy will be a series of large, uniform landscapes recovering from wildfires and other widespread ecosystem setbacks. These landscapes will present future societies with a set of limited options and needlessly high costs that, in many ways, will mirror today's situation. Both now and in the future, the preferred situation is a more diverse, heterogeneous landscape that is more consistent with the historical range of variability, less susceptible to wide-area disturbances, and thus more easily sustainable.

FORESTS AT RISK

The forests at greatest risk are composed of an unsustainable combination of tree species, densities, and age structures that are susceptible to the fire and drought regimes common to the region. This is a particular problem in forests where the species mix has shifted dramatically away from ponderosa and other long-needled pines and toward firs. This species shift, attributable to a combination of logging, grazing, fire suppression, and related activities over the past century, has been well documented.

In a review of Idaho forest data for the period 1952 to 1987, Jay O'Laughlin of the University of Idaho found that western white pine and ponderosa pine components in Idaho forests had declined 60 percent and 40 percent respectively, while true firs, Douglas-fir, and lodgepole pine had increased 60, 39, and 15 percent. In Arizona's Coconino National Forest, Wallace Covington and Margaret Moore estimated that stem counts on basalt-derived soils had shifted from a pre-settlement average of 23 trees per acre to 851 today. On the Kaibab National Forest, presettlement tree densities on limestone soils averaged 56 per acre, compared to 276 today.

Under these altered conditions, competition for moisture and nutrients creates stress that exacts a significant toll in reduced growth, while opening the way for epidemic outbreaks of insects, disease, and wildfire. Wildfires in these ecosystems have gone from the high-frequency, low-intensity patterns that historically shaped and sustained the system to numerous high-intensity fires that require enormously costly suppression attempts, which often prove futile in the face of overpowering fire intensity. High fuel loads, related to the long-time absence of fire, and dead and dying trees, resulting from insects and diseases, have fed fire intensities, resulting in the destruction of soils, watersheds, fisheries, and other ecosystem components.