Reactive forest management can also be proactive for wood-living beetles in hollow oak trees

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The debate about whether proactive (focused on irreplaceable species) or reactive (focused on vulnerable species) conservation is more effective usually focuses on the global or multinational scale and knowledge of how these principles interact on-the-ground is lacking. Here we use the first long-term dataset on an entire oak-living beetle community in hollow oaks (Quercus spp.) to ask whether policy-driven conservation actions aimed at vulnerable species can also be proactive for unthreatened, but irreplaceable species. Hollow oaks are vital keystone structures that are rich in both vulnerable and irreplaceable wood-living beetles. We sampled in excess of 23,000 individuals from 307 species over four seasons, across the oak range in Norway. We assessed the importance of key environmental variables for vulnerable, irreplaceable and generalist species. We show that simple management actions taken to benefit vulnerable species in hollow trees could also contribute to preventing the decline of important, irreplaceable species. Clearing regrowth is predicted to increase vulnerable species richness by 75–100%, specialist richness by 65%, and to benefit two generalist species. Regrowth clearance is likely to be similarly beneficial in all oak-based habitats with hollow trees across Europe and North America. Increased oak circumference and local habitat quantity were also beneficial for species richness and influenced species composition. Based on this we provide advice for targeting conservation action. We suggest economic, carbon and recreational benefits of clearance that could increase the attractiveness of conservation for policy-makers. We show the importance of examining large-scale conservation planning principles at a local scale to elicit how they work on the ground where conservation actually happens.