Reassessment of the risks of climate change for terrestrial ecosystems

SUMMARY Forecasting the risks of climate change for species and ecosystems is necessary for developing targeted conservation strategies. Previous risk assessments mapped the exposure of the global land surface to changes in climate 1–4 However, this procedure is unlikely to robustly identify priority areas for conservation actions because non-linear physiological responses and co-limitation processes ensure that ecological changes will not map perfectly to the forecast climatic changes. Here, we combine ecophysio­logical growth models of 135,153 vascular plant species and plant growth form information to transform ambient and future climatologies into phytoclimates, which describe the ability of climates to support the plant growth forms that characterise terrestrial ecosystems. We forecast that 33% to 68% of the global land surface will experience a significant change in phytoclimate by 2070 under RCP 2.6 and RCP 8.5, respectively. Novel phytoclimates without present-day analogue are forecast to emerge on 0.3-2.2% of the land surface, and 0.1-1.3% of currently realised phytoclimates are forecast to disappear. Notably, the geographic pattern of change, disappearance and novelty of phytoclimates differs markedly from the pattern of analogous trends in climates detected by previous studies 1,3,4 , thereby defining new priorities for conservation actions and highlighting the limits of using untransformed climate change exposure indices in ecologicaI risk assessments. Our findings suggest that a profound transformation of the biosphere is underway and emphasise the need for a timely adaptation of biodiversity management practices.