In what may be the most significant regulatory backdown in state history, the Oregon Board of Forestry yesterday sharply reduced its obligation to review private timber sales on landslide-prone land. In the past, the state forester was required to approve all such logging and could be held liable if an approved project later resulted in harm to a threatened or endangered species. By changing the rule, the forestry board hopes to limit the state’s liability for damage done to salmon should logged hillsides collapse into streams and damage habitat. The rule-change means the state will no longer have to enforce the federal Endangered Species Act, which frequently holds timber operations to tougher standards than does Oregon’s Forest Practices Act; instead, timber companies themselves will have to comply with federal law. Environmental organizations plan to appeal the change.