Global warming, habitat shifts and potential refugia for biodiversity conservation in the neotropical Guayana Highlands

Current global average temperatures are 2 °C cooler than during the last interglacial period. The expected increase in temperature during the 21st century will be most stressful for cold-adapted and stenothermic mountain species, forcing them to migrate upwards, and eventually to concentrate into either large areas with favourable climates (refugia) or small stands under locally favourable microclimates (microrefugia). We investigate potential refugia in the neotropical Guayana Highlands mountain biome (Pantepui), consisting of ∼50 isolated table mountains (tepuis), to develop strategies for conserving biodiversity during future global warming. We predict the amount of loss of altitudinal habitats of endemic vascular flora of 26 tepuis and evaluate potential threats to these taxa with respect to species extinction, habitat loss, habitat connectivity and the degree of isolation. We compare past, present and future Pantepui landscape configurations through fragmentation analysis and identify potential in situ refugia. Spatial analysis forecasts more species isolation and declining biodiversity at the end of this century relative to current and past levels. Habitats are predicted to experience >80% loss, with the disappearance of 38 habitat patches. One large patch (Chimantá massif) accounts for 46% of the predicted remaining habitat. This patch can be considered a potential refugium for future vascular flora, as it is predicted to contain some present-day resistant species from lower altitudinal levels and other species eventually persisting in microrefugia. The easternmost Pantepui district, containing the Chimantá massif and other tepuis, seems to be the most suitable for the application of in situ conservation strategies.