Attributing future Amazon forest loss to land-use change and climate change

Abstract

The Amazon rainforest is of vital importance for biodiversity, regional climate, as well as global water and carbon cycling. However, over the past decades, ecosystem functions of the Amazon rainforest have diminished through a combination of increasing anthropogenic pressure in form of land-use change and intensifying natural disturbances. Recent studies suggest that unabated deforestation and climate change could tip large parts of the Amazon towards a different, savanna-like vegetation state. Although such a scenario could lead to severe impacts on the climate system from regional to global scales, a holistic assessment of the risk of large-scale Amazon forest loss due to land-use change and climate change in the 21st century is currently lacking.  Here, we use data from multiple CMIP6 Earth System Models under two low climate mitigation scenarios to attribute Amazon forest loss until 2100 to land-use change and climate change, applying a novel ensemble member approach. We find that around 1 mio. km2 of forest will diminish by 2100, corresponding to a loss of around one fifth of the pre-industrial forest area. Historically and over the first half of the 21st century, land-use change is the main driver of forest loss, whereas forest loss due to climate change increases non-linearly beyond 2°C global warming and even exceeds forest loss caused by land-use change by the end of the century in some models. We further find a consistent increase in the probability of abrupt (rather than gradual) forest loss with progressing deforestation and climate change.  Overall, our results highlight that under plausible low mitigation socio-economic pathways 1) the Amazon rainforest will substantially diminish due to anthropogenic climate and land-use change and 2) the risk of forest loss due to climate change increases significantly beyond 2°C global warming. This stresses the urgent need for increased efforts to reduce deforestation and forest degradation through forest protection, conservation and sustainable land-use practices and for climate mitigation efforts in line with the Paris Agreement.