To early settlers and loggers, the forests of Oregon's Coast Range seemed endless and inexhaustible. But in less time than it took to grow them, most of the original forests were harvested. Recent analysis by researchers at Oregon State University and the U.S. Forest Services Pacific Northwest Research Station suggests that old growth covered an average of 48 percent of the Coast Range over the past 3,000 years and that forests containing trees greater than 80 years old covered an average of 71 percent of the land.

These forests were and still are important to salmon. Aquatic scientists have studied the effects timber harvest on fish habitat for decades. They have learned that throughout the past century and a half, logging, road building and related activities damaged salmon freshwater habitat. Gordon Reeves, a fish biologist with the U.S. Forest Service Aquatic and Land Interactions (ALI) Team, investigates the impact of forestry throughout the Pacific Northwest, from Alaska to Oregon. He says we have changed our forest ecosystems in profound ways in terms of salmon habitat.

Logging practices and associated road
building have damaged salmon habitat
(Forests and Forestry: College of Forestry
Photographs (P 61), Subgroup 2, 979-11-102;
Courtesy of Oregon State University Libraries,
University Archives)

Examples of earlier damaging practices:

• In the 1800s, trees were frequently removed from wooded riversides and coastlines and floated away to mill sites. When the timber within easy access of a navigable stream or river was exhausted, logging operations moved on
• Heavily logged river valleys resulted in unstable soils, higher water temperatures and increased sediment deposits in spawning gravel. Food for fish declined, and the supply of large, woody debris that naturally formed the structure for fish habitat disappeared
• Early logging operations built temporary structures called "splash dams" across small streams in more than 160 locations on Oregon's coastal streams and Columbia River tributaries. First, a dam was built and filled with water. When it was blown up, mammoth logs roared downstream in a huge torrent. These torrents of water and logs would scour stream bottoms as logs pushed gravel off stream bottoms, leaving bare bedrock. Salmon, their habitat and their offspring were often destroyed
• After World War II, heavy equipment was used to harvest trees. Yarders, loaders, bulldozers and trucks came down extensive networks of newly built roads into areas formerly inaccessible to timber harvest. On federal lands, there is now an average of between three and four miles of road per square mile of watershed area, according to a 1993 Federal Ecosystem Management Assessment Team Report. Forest Service studies showed that where roads were built on steep terrain in the 1940s through the 1960s, the frequency of landslides increased dramatically compared to steep roadless terrain
• Mechanized timber harvest and associated road construction increased sediment into streams and raised stream temperatures. Inadequately designed road culverts blocked salmon migration to spawning areas. Until the 1980s, large woody debris was often removed from salmon streams because biologists thought it helped fish migrate upstream to spawn

Since the 1990s, logging now has less impact on forest soils, water, and fish due to harvest of smaller trees with new techniques, lighter machines, better road practices and replacement of barriers to migration with new culverts and bridges.

However, Bill Arsenault, who operates a small woodland farm near Elkton and is a vice president of the Oregon Small Woodlands Association, is working to address this lack of large woody debris in streams. "What I'm doing on my place primarily is putting wood back in the streams. This is very important as an interim step [in improving salmon habitat]. Current forest practices are designed to allow the natural system to put wood back in the streams. But that's a long-term process."

Although timber practices are now changing for the better and public land managers are now protecting more areas for natural, non-consumptive uses including wilderness, wildlife, fisheries and water quality, the salmon will be affected by past forest practices for many decades, said Reeves.

Sources - Floods

Sources - Tsunamis

Compiled by John Ame, Science Writer (2007); Revised by Hal Salwasser, Dean, OSU College of Forestry