Abstract
The Corsican Nuthatch (Sitta whiteheadi) is red-listed as vulnerable to extinction by the IUCN because of its endemism, reduced population size, and recent decline. A further cause is the fragmentation and loss of its spatially-restricted favourite habitat, the Corsican pine (Pinus nigra laricio) forest. In this study, we aimed at estimating the potential impact of climate change on the distribution of the Corsican Nuthatch using species distribution models. Because this species has a strong trophic association with the Corsican and Maritime pines (P. nigra laricio and P. pinaster), we first modelled the current and future potential distribution of both pine species in order to use them as habitat variables when modelling the nuthatch distribution. However, the Corsican pine has suffered large distribution losses in the past centuries due to the development of anthropogenic activities, and is now restricted to mountainous woodland. As a consequence, its realized niche is likely significantly smaller than its fundamental niche, so that a projection of the current distribution under future climatic conditions would produce misleading results. To obtain a predicted pine distribution at closest to the geographic projection of the fundamental niche, we used available information on the current pine distribution associated to information on the persistence of isolated natural pine coppices. While common thresholds (maximizing the sum of sensitivity and specificity) predicted a potential large loss of the Corsican Nuthatch distribution by 2100, the use of more appropriate thresholds aiming at getting closer to the fundamental distribution of the Corsican pine predicted that 98% of the current presence points should remain potentially suitable for the nuthatch and its range could be 10% larger in the future. The habitat of the endemic Corsican Nuthatch is therefore more likely threatened by an increasing frequency and intensity of wildfires or anthropogenic activities than by climate change.
Highlights
The main causes of current species extinctions are the destruction and fragmentation of habitats, invasion by alien species and climate change [1]
We can note that for the Corsican pine, the potential future distribution obtained with the lowest probability threshold (LPT) is very close to the current distribution obtained with the the presences points (TSS) threshold: almost all current Corsican pine presences are included in the future distribution obtained with the LPT (Fig. 4)
The potential impacts of climate change on the nuthatch distribution will result from climate change impacts on the Corsican pine
Summary
The main causes of current species extinctions are the destruction and fragmentation of habitats, invasion by alien species and climate change [1] Some of these factors can have amplified consequences on threatened species on islands, which have been highly vulnerable to recent human activities [2,3,4,5,6]. The Corsican Nuthatch is red-listed as vulnerable to extinction by the International Union for the Conservation of Nature [11] because of its endemism, reduced population size (1,557–2,201 territories) [10] and recent decline, and because its favourite habitat, the mature Corsican pine forest, is currently spatially-restricted (less than 16,000 ha) and decreasing in extend because of fires and logging [12]. Climate change might be a further threat to this island endemic tree, either directly by shifting suitable climatic conditions further up in altitude, or indirectly by increasing the frequency and/or intensity of forest fires
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