On some public forests in Oregon, forest managers are using a timber harvest method called variable-retention harvest. In a variable-retention harvest, timber is logged in patches of varying sizes, leaving behind certain trees or clusters of trees to protect wildlife habitat or serve other ecological needs.
The Bureau of Land Management uses the silvicultural method in southwestern Oregon to design harvests with the competing goals of generating timber revenue while also protecting forest habitat for species such as the threatened northern spotted owl.
Variable-retention harvest involves carefully planning a series of patch cuts that mimic clearings in the forest created by a wildfire or other natural disturbance. These forest clearings are important habitat for deer, elk, butterflies, songbirds and small mammals.
At the same time, the BLM preserves stands of older trees as habitat for the northern spotted owl and the marbled murrelet, a seabird that flies inland to nest in forests. Before each harvest, a team of foresters, fish and wildlife biologists, and other resource specialists inspects the proposed site. They mark areas with streams, sensitive areas and other vital plant and animal habitat as protected from the harvest. Hardwoods and other trees species that contribute to overall biodiversity of the forest are preserved.
Because of the diverse management goals behind a variable-retention harvest, it falls somewhere between thinning and clearcutting. More trees are harvested than a thinning, but fewer than in clearcutting.
Variable-retention harvesting is being used by the Bureau of Land Management in southwestern Oregon to find a balance between its economic and ecological objectives.