America's Forests
1999 Health UpdateOverview MapIntroduction
Issues and Examples of Forest Ecosystem Health Concerns
IV. Loss of Biodiversity

Tied to the previous issues, but important enough in its own right, is the concern over the loss of biodiversity. Exotic insects and diseases may lead to the loss of biodiversity on all levels of the landscape. Western white pine has decreased by 95 percent due to white pine blister rust across its natural range in the West. Whitebark pine is also in decline due to the same disease. The introduction of the American chestnut blight from Asia led to the loss of an ecologically important species from deciduous eastern forests of the United States. As a result of the introduction of exotic grasses and forbs, the amount and diversity of native vegetative cover has decreased in riparian ecosystems. Examples of the impact of these exotic species is discussed earlier in this report. U.S. forests are riddled with more examples.

Examples

Port-Orford Cedar Root Disease—Port-Orford cedar has a distribution limited to southwestern Oregon and northwestern California. It is an essential component of riparian vegetation in significant portions of its range. An exotic root disease threatens this species in much of its range. Loss of Port-Orford cedar affects stream habitat for endangered species of salmon and rare plants. Current efforts of the USDA Forest Service and its partners to manage Port-Orford cedar root disease include preventing or slowing the spread of the pathogen into uninfested areas and breeding trees for resistance to the disease organism.

Port-Orford cedar resistant to root disease Port-Orford cedar susceptible to root disease

Humans have been the main vectors in spreading the spores of the pathogen that causes Port-Orford cedar root disease. Major spread to new watersheds has occurred through the movement of dirt in road construction, road maintenance, mining, and recreational traffic flow on forest roads. To limit spread, a combination of management activities are being used, including (a) excluding entry in roadless areas, (b) establishing road closures (both permanent and seasonal), (c) using sanitation treatments, and (d) educating forest workers and users about how the disease spreads and how to avoid activities that may enhance the spread of the pathogen. Methods to slow the spread of Port-Orford cedar root disease are considered during the planning of all projects carried out on the national forests within the range of Port-Orford cedar.

The USDA Forest Service, U.S. Department of the Interior Bureau of Land Management, and Oregon State University are cooperating in a program to identify trees resistant to this disease. In the past 2 years, over 7,000 candidate trees have been screened. To establish a breeding and conservation orchard, collections have been made from the 961 best performers. Results of the resistance effort are encouraging. Outplanting tests of the most resistant families have survived for more than 5 years in the presence of high levels of spore loads.

Butternut Canker—Butternut Canker, a disease of unknown origin, is a major threat to butternut in the United States. Ecologically, butternut is an important source of wildlife mast (food), especially in the northern parts of its range where walnut is not present. It is also valued for its specialty products and carving. In the last 15 years, there has been a dramatic decrease in the number of live butternut trees. For example, butternut decreased by 58 percent in Wisconsin and 84 percent in Michigan. Butternut has been hit hard, and the slow, systematic loss of the infected trees causes concern for the viability of the species. It is currently listed under the Endangered Species Act in a vulnerable category. The USDA Forest Service has developed management guidelines to create stand conditions that will result in the regeneration of this species. We also have a resistance breeding program to identify resistant seed sources for restoration and conservation of the species.

Butternut canker causes death of a valuable tree
 
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