Conserving biological diversity (biodiversity) means keeping healthy populations of all plants and animals naturally occurring in forests. In Oregon, for example, there are 329 species of mammals, birds, reptiles, and amphibians that live at least part of their lives in the forest. In the past 150 years, five species of mammals and six species of birds have disappeared from a significant portion of, or entirely from, the area where they used to live. These include such well-known species as the grizzly bear, gray wolf, and northern spotted owl.

A number of other species of plants and animals are sensitive to disturbance(things like fire and timber harvesting). Scientists are working to find out which species are most at risk, and how best to protect them from extinction. Timber harvest is currently restricted on about 30 to 35% of Oregon's forest lands, in order to protect wildlife, wilderness, or other non-market values.

On the map at right, restricted lands are shown in dark green, blue, red, pink, and orange.

Map courtesy of Oregon Department of Forestry

Most scientists believe that the best way to conserve biodiversity is to maintain a mix of different-aged forests across the landscape. Some plants and animals require open areas and young forest stands, while others need the large trees, snags, down logs and other features that are found mostly in older forests. Under the federal government's Northwest Forest Plan, the amount of older forests will be allowed to increase from current levels.