Tropical tree mortality has increased with rising atmospheric water stress

• Published in: Nature (London) Vol. 608; no. 7923; pp. 528 - 533
• Main Authors: Bauman, David, Fortunel, Claire, Delhaye, Guillaume, Malhi, Yadvinder, Cernusak, Lucas A., Bentley, Lisa Patrick, Rifai, Sami W., Aguirre-Gutiérrez, Jesús, Menor, Imma Oliveras, Phillips, Oliver L., McNellis, Brandon E., Bradford, Matt, Laurance, Susan G. W., Hutchinson, Michael F., Dempsey, Raymond, Santos-Andrade, Paul E., Ninantay-Rivera, Hugo R., Chambi Paucar, Jimmy R., McMahon, Sean M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18.08.2022; Nature Publishing Group
• Subjects: 631/158/1745; 631/158/2165; 631/158/2450; 631/158/2454; 631/158/853; Anthropogenic factors; Atmospheric water; Biodiversity; Biodiversity and Ecology; Botanics; Carbon; Carbon budget; Carbon sequestration; Carbon sinks; Climate change; Climate prediction; Cyclones; Ecology, environment; Ecosystems; Environmental Sciences; Forests; Global warming; Health risks; Humanities and Social Sciences; Life expectancy; Life Sciences; Life span; Local climates; Mortality; Mortality risk; multidisciplinary; Risk; Science; Science (multidisciplinary); Species; Systematics, Phylogenetics and taxonomy; Threatened species; Trees; Tropical environments; Tropical forests; Vapor pressure; Vegetal Biology; Water stress; Community ecology; Population dynamics; Tropical ecology; Climate-change ecology; Forest ecology
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-022-04737-7

Evidence exists that tree mortality is accelerating in some regions of the tropics 1 , 2 , with profound consequences for the future of the tropical carbon sink and the global anthropogenic carbon budget left to limit peak global warming below 2 °C. However, the mechanisms that may be driving such mortality changes and whether particular species are especially vulnerable remain unclear 3 – 8 . Here we analyse a 49-year record of tree dynamics from 24 old-growth forest plots encompassing a broad climatic gradient across the Australian moist tropics and find that annual tree mortality risk has, on average, doubled across all plots and species over the last 35 years, indicating a potential halving in life expectancy and carbon residence time. Associated losses in biomass were not offset by gains from growth and recruitment. Plots in less moist local climates presented higher average mortality risk, but local mean climate did not predict the pace of temporal increase in mortality risk. Species varied in the trajectories of their mortality risk, with the highest average risk found nearer to the upper end of the atmospheric vapour pressure deficit niches of species. A long-term increase in vapour pressure deficit was evident across the region, suggesting that thresholds involving atmospheric water stress, driven by global warming, may be a primary cause of increasing tree mortality in moist tropical forests. Over the past 35 years, annual tree mortality risk has increased in the moist tropical forests of Australia and is associated with increased atmospheric water stress.