Tropical ecosystems store over half of the world’s aboveground live carbon as biomass, and water availability plays a key role in its distribution. Although precipitation and temperature are shifting across the tropics, their effect on biomass and carbon storage remains uncertain. Here we use empirical relationships between climate and aboveground biomass content to show that the contraction of humid regions, and expansion of those with intense dry periods, results in substantial carbon loss from the neotropics. Under a low emission scenario (Representative Concentration Pathway 4.5) this could cause a net reduction of aboveground live carbon of ~14.4–23.9 PgC (6.8–12%) from 1950–2100. Under a high emissions scenario (Representative Concentration Pathway 8.5) net carbon losses could double across the tropics, to ~28.2–39.7 PgC (13.3–20.1%). The contraction of humid regions in South America accounts for ~40% of this change. Climate mitigation strategies could prevent half of the carbon losses and help maintain the natural tropical net carbon sink.
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CRU v.4.04 data can be downloaded from the CRU website (https://crudata.uea.ac.uk/cru/data/hrg/). Downscaled climate data from the Coupled Model Intercomparison Project Phase 5 (CMIP5) multimodel ensemble can be downloaded from https://gdo-dcp.ucllnl.org/downscaled_cmip_projections/dcpInterface.html. Global biomass data is available from https://developers.google.com/earth-engine/datasets/catalog/WHRC_biomass_tropical)2, https://doi.org/10.5281/zenodo.4161694 (ref. 3) and https://catalogue.ceda.ac.uk/uuid/5f331c418e9f4935b8eb1b836f8a91b8 (ref. 20). MODIS Land Cover data is available at https://lpdaac.usgs.gov/products/mcd12q1v006/. Continent borders are from the Environmental Systems Research Institute’s World Continents shapefiles v.10.3 (http://gis.ucla.edu/geodata/dataset/continent_ln)53. Preprocessed input data (as specified in the manuscript), partial results and final predictions of changes in area and biomass are available in a public repository via Dryad54.
Relevant R scripts used to process the data and perform the analyses are available in a public repository via Dryad54.
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We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups (listed in Supplementary Table 4) for producing and making available their model outputs. For CMIP, the U.S. Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provided coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. This research was supported through funding from the National Science Foundation (MSB-ECA award no. 1802754; INFEWS/T1 award no. 1739724).
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Extended Data Fig. 1 Distribution of climatic zones in the tropics for Historic and Future 30-year time periods (1950–1979, 1980–2009, 2010–2039, 2040–2069, and 2070–2099).
Colors represent the climatic zones. Contour lines in the maps and gray dashed lines in the scatterplots are plotted for reference to show the distribution and limits of the climatic zones in the period 1950–1979. Climate data from CRU v.4.0445 for 1950–2009 and from CMIP5 projections46,47 for 2010–2099 under RCP 8.5.
Extended Data Fig. 2 Individual model projections of precipitation and MCWD under RCP 8.5.
Dots represent each model’s mean Historic (1950–1979) climate for each climatic zone. Connected arrowheads represent average climate at the end of the century (2070–2099). The black shapes correspond to the average climate from all models. Models used are listed in Supplementary Table 1. Climate data from CRU v.4.0445 for 1950–2009 and from CMIP5 projections46,47 for 2010–2099 under RCP 8.5.
Extended Data Fig. 3 Biomass and biomass changes across the tropics under all scenarios.
Extended Data Fig. 4 Changes in carbon (Pg) in the tropics under RCP 8.5.
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Uribe, M.d.R., Coe, M.T., Castanho, A.D.A. et al. Net loss of biomass predicted for tropical biomes in a changing climate. Nat. Clim. Chang. 13, 274–281 (2023). https://doi.org/10.1038/s41558-023-01600-z