Quantifying the effectiveness of habitat management to counter local extinction: A case-study on capercaillie

Abstract

The degradation of forest habitats in managed forests is a major threat to biodiversity. Accordingly, the conservation of forest-dwelling species has to be integrated with other goals and paradigms of production forestry. As those objectives may differ, it is crucial to quantify the potential effectiveness of habitat management for conservation to demonstrate its actual value. Here, we analysed detailed field-based distribution maps of a declining population of capercaillie (Tetrao urogallus), an indicator of open, structurally diverse conifer-dominated forests, in southwestern Germany to quantify the potential effect size of habitat management. We modelled range loss dynamics as a function of habitat structures obtained from high-resolution aerial stereo imagery, in order to estimate the potential increase in the probability of local capercaillie persistence under different management scenarios. Furthermore we identified situations in which habitat management would produce the largest conservation benefits. The probability of local capercaillie persistence during the study period was positively related to population connectivity, winter snow height and the availability of suitable forest structures. The positive effect of habitat management was largest at sites where persistence probability would otherwise be low to intermediate. Potential negative effects of decreasing snow load under climate change on local capercaillie persistence could be compensated more effectively by habitat improvement than a lack of population connectivity, implying that focusing habitat management on the edges of the distribution in addition to core areas would maximize conservation returns. Our results may thus contribute to an effective allocation of conservation investments where their leverage is highest.