Official conservation efforts for the northern spotted owl began in the United States in 1975 when it was declared “threatened” in the state of Oregon; efforts continued in a sporadic and unsystematic way through the 1980s. In 1989 the Interagency Scientific Committee (ISC) was established by Congress and charged with the development of a scientifically defensible conservation strategy covering the entire range of the northern spotted owl, which includes parts of the states of Oregon, Washington, and California. The ISC collated all spotted owl research and approached questions concerning the need for a conservation strategy and the efficacy of potential reserve designs as testable hypotheses. Because the hypothesis tests were based on incomplete data and highly stylized population models, uncertainty concerning the conclusions of the ISC remained. Subsequent research focused on answering those uncertainties, and here we revisit the ISC's conclusions, asking which if any of them have been invalidated. The ISC's major conclusions have remained robust: he population of spotted owls is declining due to reductions in old growth habitat. Subsequent trend-analyses confirmed the levels of population decline calculated by the ISC and in addition concluded that the rate of decline was accelerating. The ISC's response to these conclusions was to recommend the establishment of an extensive network of large reserves. Subsequent research and more detailed computer modeling have confirmed the conceptual validity of this conservation plan but suggest that optimistic assumptions led the ISC to propose a minimal reserve structure. Current federal management plans in the Pacific Northwest propose more habitat than the ISC envisioned, providing a greater likelihood of persistence.


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  • Article Type: Review Article
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