Abstract
Tropical terrestrial ecosystems play an important role in modulating the global carbon balance. However, the complex dynamics and factors controlling tropical aboveground live biomass carbon (AGC) are not fully understood. Here, using remotely sensed observations, we find a moderate net AGC sink of 0.21â±â0.06âPgCâyrâ1 throughout the global tropics from 2010 to 2020. This arises from a gross loss of â1.79âPgCâyrâ1 offset by a marked gain of 2.01â±â0.06âPgCâyrâ1. Fire emissions in non-forested African shrubland/savanna biomes, coupled with post-fire carbon recovery, substantially dominated the interannual variability of tropical AGC. Fire radiative power was identified as the primary determinant of the spatial variability in AGC gains, with soil moisture also playing a crucial role in shaping trends. We highlight the dominant roles of anthropogenic and hydroclimatic determinants in orchestrating tropical land carbon dynamics and advocate for land management to conserve indispensable ecosystem services worldwide.
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Data availability
The L-VOD data are available at the SMOS-IC website (https://ib.remote-sensing.inrae.fr/). The TMF data are available at https://forobs.jrc.ec.europa.eu/TMF. The van Wees fire emission data were downloaded from ref. 29 (https://zenodo.org/records/7229675). The GFED5 burned area data are available via Zenodo at https://doi.org/10.5281/zenodo.7668423 (ref. 59). The ESA-CCI AGB data are available at https://climate.esa.int/en/odp/#/project/biomass. The Zarin AGB data are available at https://data.globalforestwatch.org/datasets/3e8736c8866b458687e00d40c9f00bce_0/about. The Avitabile AGB data are available at http://lucid.wur.nl/datasets/high-carbon-ecosystems. The Baccini AGB data are available at https://developers.google.com/earth-engine/datasets/catalog/WHRC_biomass_tropical. The two Jet Propulsion Laboratory AGB maps are available at https://gfw2-data.s3.amazonaws.com/forest_cover/zip/tropical_forest_carbon_stocks.tif.aux.zip and https://zenodo.org/records/7583611(ref. 48), respectively. The atmospheric CGR data are available at https://gml.noaa.gov/. The links to the predictors for BRT models are provided in the Supplementary Information. The baseline map for map figures was obtained from GADM (https://gadm.org/). The generated maps of AGC losses and gains are available online at https://data.tpdc.ac.cn/zh-hans/data/97a05aa3-5d4f-4e44-99d1-e474166e62a6.
Code availability
The scripts used to generate all the results are MATLAB (2022B). The code is available from the corresponding author on request.
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Acknowledgements
This research has been funded by the European Space Agency Climate Change Initiative (ESA-CCI) Biomass project (ESA ESRIN/ 4000123662) and RECCAP2 project 1190 (ESA ESRIN/ 4000123002/18/I-NB). J.-P.W. acknowledges support from the CNES (Centre National dâEtudes Spatiales) TOSCA programme. P.C. and J.-P.W. acknowledge support from the One Forest Vision programme of the French Ministry of Research. This study was also supported by the CALIPSO (Carbon Losses in Plants, Soils and Ocean) funded through the generosity of Eric and Wendy Schmidt by recommendation of the Schmidt Futures programme.
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P.C., J.-P.W. and Y.F. designed the research. Y.F. performed the analysis. X.L. and J.-P.W. prepared the raw SMOS-IC L-VOD data. D.v.W prepared the fire emission product. Y.F. and P.C. wrote the draft. All authors contributed to the interpretation of the results and the writing of the paper.
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Nature Climate Change thanks Roger Auch, Rico Fischer, Graciela Tejada and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Extended data
Extended Data Fig. 1 Extent of the study region over the tropics.
a, availability of valid L-VOD observations. b, availability of TMF products. c, final study domain. The tropics are defined as the regions between 23.5°N and 23.5°S but excluding Australia, following our previous studies11. The final study domain covers the tropical regions covered by valid L-VOD observations and TMF products.
Extended Data Fig. 2 L-VOD-based AGC changes for each loss and gain process.
AGC gross losses comprise three parts, including fire emissions, deforestation and forest degradation through non-fire means. Fire emissions, encompassing both forest and non-forest areas, were estimated utilizing the van Wees fire emission product29. Non-fire deforestation and forest degradation were quantified using the Tropical Moist Forests (TMF) dataset. AGC residuals were determined by subtracting AGC losses from AGC net changes. These residuals comprise AGC changes originating from old forests and non-fire shrub/savannah loss that are not detected by TMF, and vegetation regrowth/gain, with vegetation regrowth/gain emerging as the predominant part. Consequently, the AGC residuals were deemed a proxy for AGC gross gains.
Extended Data Fig. 3 Changes in aboveground live biomass carbon (AGC) relative to 2010 from 2011â2020 over the tropics (a) and three tropical continents of America (b), Africa (c) and Asia (d).
The solid lines indicate the mean of AGC changes and shaded areas represent ±1âs.d. among the 18 estimates (see Methods).
Extended Data Fig. 4 Bivariate map of aboveground live biomass carbon (AGC) gains vs. the four most influential factors of FRP (a), Ft (b), young forest regrowth (c), and Rs (d) for spatial variability modeling.
The unit for the y-axis of the legend (AGC gains) is MgC haâ1 yrâ1.
Extended Data Fig. 5 Continental partial dependence plots of the top four variables in explaining the spatial patterns and trends in aboveground live biomass carbon (AGC) gains.
aâd, the top four variables in explaining the spatial patterns of AGC gains. The unit for the y-axis of AGC gains is MgC haâ1 yrâ1. eâh, the top four variables in explaining the trends in AGC gains. δ denotes the trends in time series. The unit for the y-axis of δAGC gains is MgC haâ1 yrâ2. Dash lines are the 30 individual estimates and solid lines are the median (see Methods).
Extended Data Fig. 6 Bivariate map of trends in aboveground biomass carbon (δAGC) gains vs. the four most influential factors of δSM (a), δRs (b), Rs (c), and livestock density (d) for δAGC gains modeling.
The unit for the y-axis of the legend (AGC gains trend, that is, δAGC) is MgC haâ1 yrâ2. δ denotes the trends in time series.
Supplementary information
Supplementary Information
Supplementary Table 1 and Figs. 1â12.
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Feng, Y., Ciais, P., Wigneron, JP. et al. Global patterns and drivers of tropical aboveground carbon changes. Nat. Clim. Chang. 14, 1064â1070 (2024). https://doi.org/10.1038/s41558-024-02115-x
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DOI: https://doi.org/10.1038/s41558-024-02115-x