The Pacific Northwest Old-Growth Forest--A Unique Ecosystem

• The Pacific Northwest old-growth forest is a conifer forest, dominated by large, old trees. In the Pacific Northwest, the most common type of old-growth ecosystem is a forest dominated by Douglas-firs and western hemlocks, generally 350 to 750 years old. The youngest old-growth forests are 200 years old, and the oldest are about 1,000 years old.

- The Pacific Northwest also has old-growth forests dominated by Sitka spruce and western hemlock, along the Pacific Coast, and at higher elevations in the Cascade Range, true fir and hemlock old-growth forests.

• Among all the forests of the world, the Pacific Northwest old-growth forest is unique because of the size and old age of its trees, the accumulations of biomass (weight and density of living organisms), and the climate, with its wet, mild winters and dry, warm summers.

- No other forest has an entire group of tree species that equals the trees in the Pacific Northwest old-growth forest for their size and long lives. Some of California's giant redwoods are bigger than the biggest Douglas-fir tree. But several species of big trees grow in the Pacific Northwest old-growth forest, not just one. In other forests, some junipers and bristlecone pines live longer. But several species of trees live for hundreds of years in the Pacific Northwest old-growth forest, not just one.

• Scientists have done a lot of research on old-growth forests in the last 30 years. Much of this work was done by Pacific Northwest Research Station scientists. Click on the other headings on this page to learn more about Pacific Northwest old-growth forests.