America's Forests | Changed Ecological Conditions


		VII. Changed Ecological Conditions

As a result of a combination of many of the concerns discussed, America’s forests display many examples of habitat changes. Past management practices, combined with native and nonnative invasive species, have created landscapes in some areas that experience more frequent or intense disturbances than in the past. These lands are costly to manage, less able to provide the values that humans desire, and are not sustainable ecologically. The USDA Forest Service has begun to address this issue by using a risk mapping process to assess forest health conditions at the national scale. The risk mapping process produces risk maps that are used in combination with other tools to help determine where national attention may be needed to address forest health. The maps are used to identify broad geographic areas that need additional analysis. These maps are based on three core key data layers: (1) insects and diseases, (2) fire, and (3) wildland/urban interface. The insects and diseases layer identifies 59 million acres at risk in the United States, of which 24 million acres are on National Forest System lands.

Idaho Panhandle Douglas-Fir Bark Beetle Outbreak—Today, the Idaho Panhandle National Forest is experiencing high mortality caused by the Douglas-fir bark beetle. This infestation is merely one symptom of a larger problem. Years of successful fire fighting, past logging practices, and the infestation of white pine blister rust have resulted in substantial losses of western white pine, ponderosa pine, and larch (tamarack). Today, the forest contains almost twice as much Douglas-fir as was historically present. As a result, insects—such as the Douglas-fir bark beetle—and root rot diseases are flourishing beyond historic levels.

Figure 2. Forest Lands Most at Risk of Mortality to Insects and Diseases.

During the winter of 1996-97, snow, ice, and wind damaged Douglas-fir trees in the forests of northern Idaho and northeastern Washington. Douglas-fir bark beetles attacked standing green Douglas-fir trees in the spring and summer of the following year. In addition, the hot, dry summer in 1998 created additional stress to living Douglas-fir trees, resulting in additional beetle attacks. In the fall of 1998, Douglas-fir tree mortality occurred over a wide area of northern Idaho, with some of the most significant damage in the wildland/urban interface around Coeur d’Alene. Although the Douglas-fir beetle is a normal component of forest ecosystems, the size of this infestation is unusually large. Many areas of wildland/urban interface are affected, which is putting people’s lives and property at risk. The infestation is widespread, affecting about 125,000 acres of forest lands.

The USDA Forest Service, with other Federal and State agencies, formed a team of specialists to evaluate the magnitude of the outbreak, predict its future behavior, and develop recommendations for management. They also led efforts to increase public awareness of the problem and management options, such as removing dead trees that contribute to severe wildfires, recovering the value of dead trees before deterioration, planting pines and larch to improve species composition, and improving aquatic and wildlife habitat. The project also includes a pilot test to evaluate pheromones to alter insect behavior and impacts.

Douglas-fir bark beetle outbreak in the Idaho Panhandle National Forest

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