Increasing atmospheric humidity and CO2 concentration alleviate forest mortality risk

Liu et al. used models to predict the effects of climate change on tree mortality in 13 temperate and tropical forest biomes across the globe. When only increased temperature and changes in precipitation are considered, mortality increases in most biomes, with higher emissions models leading to increased mortality. However, when increases in CO2 concentration are included in the models, some or most of the increased mortality is alleviated for most of the biomes, with the exception of needle-leaf forests which will suffer increased mortality in all models. Interestingly, the authors also investigated the origins of tree mortality, and concluded that in some biomes the trees are likely to die due to hydraulic failure, and in others due to inadequate CO2 uptake (as a consequence of excessive stomatal closure) leading to carbon limitation. Proc. Natl. Acad. Sci. USA  10.1073/pnas.1704811114