Wildlife studies on the Tongass National Forest challenge essential assumptions of its wildlife conservation strategy

Abstract

AbstractThe Tongass National Forest in southeast Alaska, USA, includes the Alexander Archipelago and narrow North American mainland, comprising one of the largest remaining, largely pristine, coastal temperate rainforest in the world. Management of the Tongass has become increasingly challenging because of expectations of a conservation framework designed to maintain viable populations of native wildlife species while decades of extensive clearcut logging of old‐growth forests has continued. We used the findings of multiple published studies conducted on the Tongass from 1998 to 2017 to examine 4 assumptions of its wildlife conservation strategy (WCS): forest planning assessments of wildlife viability were realistic, forest management and conservation policies are implemented at appropriate ecological scales, old‐growth reserves are effective habitat conservation areas and ensure functional connectivity, and forest‐wide standards and guidelines ensure sufficient habitat for sensitive species in managed landscapes. Several ecological field studies, population and spatial analyses and modeling, and statistical analyses revealed that wildlife viability assessments to evaluate forest plan alternatives underestimated the risk of extinction by only examining individual vulnerable species rather than considering joint probabilities across multiple species; the ecological scale of management and conservation policies do not adequately consider area‐sensitive vulnerabilities of island communities as evidenced by the increasing risk of extirpation of island endemics whose populations have become isolated and reduced; old‐growth reserves are unlikely to maintain viable populations of endemic small mammals in isolation or as functionally connected metapopulations; and a spatially explicit analysis of individual home ranges demonstrated that forest‐wide standards and guidelines provide about half the breeding habitat needed by a federally listed endemic raptor, the Queen Charlotte goshawk (Accipiter gentilis laingi), of which only half of that is secure. Thus, assertions that the WCS is properly functioning as designed are dubious because a comprehensive monitoring plan has not been implemented and vital underlying assumptions are not supported by available science. We recommend 3 forest management and conservation policy adjustments: limit size and location old‐growth forest harvests, restore forests through intermediate stand management of second growth, and conduct a formal review of WCS elements and assumptions.