Seattle Public Utilities Mami Hara, General Manager/CEO

Managing the Watershed

Upland Forest Restoration

Upper taylor basin legacy200 

Logging old-growth forests often left just a few large stumps within a dense second-growth forest.

About 84% of the watershed was harvested over the past 100 years by clearcutting (see map of Forest Age pdf). Clearcuts create conditions that are very different from natural disturbances, leaving few or no large trees, snags, or down logs behind. Many of the forests regenerated through natural seeding are now very dense, have few species, and very simple habitat structure. Trees in young dense stands are typically of similar sizes, have a closed canopy of crowns, and little light reaches the forest floor. This forest structure supports few understory trees, shrubs and herbs, and thus low plant species diversity.

These uniform forests provide few habitat niches for wildlife. Scientists predict that these types of forest will take longer than naturally established forests to develop complex old-growth forest characteristics, such as large trees, snags and logs, required by many at-risk wildlife species.

woodpecker

See slideshow of a comparison of old growth and second growth forest.

Numerous studies show that these uniform young forests can be enhanced for wildlife habitat through active restoration, by increasing forest structural complexity and species diversity. Active forest habitat restoration methods include creating canopy gaps or small forest openings, creating snags and logs, planting a variety of trees and shrubs, and thinning trees to variable densities.

Passive restoration simply means protecting the forest habitat from human-caused disturbance and allowing it to slowly develop habitat structure on its own.