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- Title
Enhanced Drought Exposure Increasingly Threatens More Forests Than Observed.
- Authors
Xu, Chongyang; Liu, Hongyan; Ciais, Philippe; Hartmann, Henrik; Camarero, Jesús J.; Wu, Xiuchen; Hammond, William M.; Allen, Craig D.; Chen, Fahu
- Abstract
Forest protection and afforestation have been identified as a means to partially offset anthropogenic CO2 emissions. Yet, increasingly frequent observations of drought‐induced tree mortality are reported. Here, we applied a risk analysis framework for global drought‐induced forest mortality by examining extreme reductions in greenness and water content of forest canopies during past mortality events as well as growth recovery of surviving individual trees following stand‐scale mortality events. We defined a drought‐induced mortality risk index (DMR) that explains 80% of documented tree mortality. Rising CO2 alleviated the increase of DMR with short‐term drought, however, the observed DMR increases with long‐term drought no matter whether considering plant responses to CO2. DMR in sites where tree mortality has been observed significantly increased since the 1980s. More than that, drought exposure threatened 0.28 billion hectares of forested areas. Our framework highlights how climate change‐induced drought, especially hotter‐droughts, threatens the sustainability of global forests. Plain Language Summary: Planting trees remains one of the most effective strategies for mitigating climate change. Studies suggest that an additional 900 million hectares of new tree‐planted areas could be supported by current climate conditions. However, the benefits of massive forestation efforts may be offset by increasing drought‐induced mortality. We conducted a risk analysis based on the robust relationship between forest mortality and drought. Our findings show that drought‐induced mortality risk can identify 80.0% of documented tree mortality events. While rising CO2 levels can alleviate the increase of mortality risk in short‐term droughts, it has little effect on mortality risk during long‐term droughts. In the past decades, both short‐ and long‐term droughts have threatened 0.28 billion hectares of forested areas globally, and the mortality risk has been increasing in particular regions. Key Points: Forest mortality risk increased with drought exposure (DE) in both pulse and press droughtsRising CO2 alleviated the increase of mortality risk with pulse drought, but it has little effect on that in press droughtsDE threatened 0.28 billion hectares of global forested areas in the past decades and has been increasing in particular regions
- Subjects
TREE planting; FOREST protection; TREE mortality; FOREST canopies; CARBON emissions; THROUGHFALL
- Publication
Earth's Future, 2024, Vol 12, Issue 1, p1
- ISSN
2328-4277
- Publication type
Article
- DOI
10.1029/2023EF003705