Tropical forests are approaching critical temperature thresholds

Christopher E. Doughty (), Jenna M. Keany, Benjamin C. Wiebe, Camilo Rey-Sanchez, Kelsey R. Carter, Kali B. Middleby, Alexander W. Cheesman, Michael L. Goulden, Humberto R. Rocha, Scott D. Miller, Yadvinder Malhi, Sophie Fauset, Emanuel Gloor, Martijn Slot, Imma Oliveras Menor, Kristine Y. Crous, Gregory R. Goldsmith and Joshua B. Fisher
Additional contact information
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
Humberto R. 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, Balboa
Imma Oliveras Menor: University of Oxford
Kristine Y. Crous: Western Sydney University, Hawkesbury Institute for the Environment
Gregory R. Goldsmith: Chapman University
Joshua B. Fisher: Chapman University

Nature, 2023, vol. 621, issue 7977, 105-111

Abstract: Abstract The critical temperature beyond which photosynthetic machinery in tropical trees begins to fail averages approximately 46.7 °C (Tcrit)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 Tcrit 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 Tcrit 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 Tcrit 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 biodiversity3,4.

Date: 2023
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DOI: 10.1038/s41586-023-06391-z

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