Tropical Forests are Approaching Critical Temperature Thresholds

Authors

Christopher E. Doughty, Northern Arizona University
Jenna M. Keany, Northern Arizona University
Benjamin C. Wiebe, Northern Arizona University
Camilo Rey-Sanchez, North Carolina State University
Kelsey R. Carter, Michigan Technological University
Kali B. Middleby, James Cook University
Alexander W. Cheesman, James Cook University
Michael L. Goulden, University of California, Irvine
Humberto R. da Rocha, Universidade de São Paulo
Scott D. Miller, State University of New York at Albany
Yadvinder Malhi, University of Oxford
Sophie Fauset, University of Plymouth
Emanuel Gloor, University of Leeds
Martijn Slot, Smithsonian Tropical Research Institute
Imma Oliveras Menor, University of Oxford
Kristine Y. Crous, Western Sydney University
Gregory R. Goldsmith, Chapman UniversityFollow
Joshua B. Fisher, Chapman UniversityFollow

Document Type

Article

Publication Date

8-23-2023

Abstract

The critical temperature beyond which photosynthetic machinery in tropical trees begins to fail averages approximately 46.7 °C (T_crit)¹. However, it remains unclear whether leaf temperatures experienced by tropical vegetation approach this threshold or soon will under climate change. Here we found that pantropical canopy temperatures independently triangulated from individual leaf thermocouples, pyrgeometers and remote sensing (ECOSTRESS) have midday peak temperatures of approximately 34 °C during dry periods, with a long high-temperature tail that can exceed 40 °C. Leaf thermocouple data from multiple sites across the tropics suggest that even within pixels of moderate temperatures, upper canopy leaves exceed T_crit 0.01% of the time. Furthermore, upper canopy leaf warming experiments (+2, 3 and 4 °C in Brazil, Puerto Rico and Australia, respectively) increased leaf temperatures non-linearly, with peak leaf temperatures exceeding T_crit 1.3% of the time (11% for more than 43.5 °C, and 0.3% for more than 49.9 °C). Using an empirical model incorporating these dynamics (validated with warming experiment data), we found that tropical forests can withstand up to a 3.9 ± 0.5 °C increase in air temperatures before a potential tipping point in metabolic function, but remaining uncertainty in the plasticity and range of T_crit in tropical trees and the effect of leaf death on tree death could drastically change this prediction. The 4.0 °C estimate is within the ‘worst-case scenario’ (representative concentration pathway (RCP) 8.5) of climate change predictions² for tropical forests and therefore it is still within our power to decide (for example, by not taking the RCP 6.0 or 8.5 route) the fate of these critical realms of carbon, water and biodiversity^3,4.

Comments

This article was originally published in Nature, volume 621, in 2023. https://doi.org/10.1038/s41586-023-06391-z

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Recommended Citation

Doughty, C.E., Keany, J.M., Wiebe, B.C. et al. Tropical forests are approaching critical temperature thresholds. Nature 621, 105–111 (2023). https://doi.org/10.1038/s41586-023-06391-z

Copyright

Springer