January 06, 2023

Climate Change Likely to Cause More Windthrows in the Amazon

The connection between convective storms and tree mortality in the Amazon projects a large increase in future windthrow events.

The spatial pattern of windthrows matches well with convective available potential energy (CAPE), which represents the favorable environment to produce storms.

[Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0) from Feng, Y., et al. "Amazon Windthrow Disturbances Are Likely to Increase with Storm Frequency Under Global Warming." Nature Communications 14, 101 (2023). DOI:10.1038/s41467-022-35570-1.]

The Science

A leading cause of tree mortality in the Amazon is windthrow, i.e., trees broken or uprooted by high winds and heavy rainfall in extreme storms. In this study, researchers built a linkage between extreme storms in the atmosphere and forest mortality on the land surface. As global warming makes extreme storms more intense, projected storms are likely to make tree mortality by windthrow commonplace over about 50% more of the Amazon by the century’s end.

The Impact

Amazon forests play important roles in regulating the global carbon cycle, but variable natural disturbances increase uncertainty of the carbon capacity. Extreme storms are important drivers of tree mortality in the Amazon region. In this study, researchers provide a framework for representing coupling between land surface forest mortality and atmospheric extreme storms. This analysis highlights potential for predicting the rate of future storm-driven tree mortality, which is not currently included in global models and emphasizes the need to improve land-atmosphere relationship in models.

Summary

Forest mortality caused by convective storms (windthrow) is a major disturbance in the Amazon. However, linkage between surface windthrows and convective storms in the atmosphere remains unclear. In addition, current Earth system models (ESMs) lack mechanistic links between convective wind events and tree mortality. In this study, researchers manually map 1,012 large windthrow events encompassing 30 years from 1990–2019 and generate hourly convective available potential energy (CAPE) from ERA5 reanalysis data. An empirical relationship is found that maps CAPE, which is well simulated by ESMs, to the spatial pattern of large windthrow events. This relationship builds connections between strong convective storms and forest dynamics in the Amazon. Based on the relationship, the model projects a 51% ± 20% increase in the area favorable to extreme storms and a 43 ± 17% increase in windthrow density within the Amazon by the end of this century under the high-emission scenario (SSP 585). These results indicate significant changes in tropical forest composition and carbon cycle dynamics under climate change.

Principal Investigator

Yanlei Feng
University of California–Berkeley
ylfeng@berkeley.edu

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
brian.benscoter@science.doe.gov

Funding

This research was supported as part of the Next-Generation Ecosystem Experiments Tropics (NGEE Tropics), which is funded by the Biological and Environmental Research (BER) program within the U.S. Department of Energy’s (DOE) Office of Science under contract number DE-AC02-05CH11231. The World Climate Research Programme’s Working Group on Coupled Modelling coordinated and promoted the Coupled Model Intercomparison Project Phase 6 (CMIP6). Support was also received from climate modeling groups, the Earth System Grid Federation (ESGF), and multiple funding agencies that support CMIP6 and ESGF.

References

Feng, Y., et al. "Amazon Windthrow Disturbances Are Likely to Increase with Storm Frequency Under Global Warming." Nature Communications 14 101 (2023). https://doi.org/10.1038/s41467-022-35570-1.