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Reply to: Little evidence that Amazonian rainforests are approaching a tipping point

Nature Climate Change volume 13, pages 1321–1323 (2023)Cite this article

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The Original Article was published on 09 November 2023

replying to S. Tao et al. Nature Climate Change https://doi.org/10.1038/s41558-023-01853-8 (2023)

Tao et al.1 raise concerns with our publication2 (Boulton et al. hereafter), which used vegetation optical depth (VOD) from the VOD Climate Archive (VODCA) product3 and normalized difference vegetation index (NDVI) from the Advanced Very-High-Resolution Radiometer4 to show that the Amazon rainforest has lost resilience since the early 2000s. We have grouped these into three main concerns. (1) The VOD data are contaminated by soil moisture, resulting in erroneously high anomalies during two major flood events. (2) Varying signal-to-noise ratios (SNRs) in the VODCA time series, due to merging different sensors, affect the resilience results. (3) The loss of resilience was weaker, and began later, in 2011 rather than the early 2000s, on the basis of lag-1 temporal autocorrelation (AR(1)) of a radar-based vegetation dataset5. We address each of these concerns in detail below.

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Fig. 1: Time series of the Ku-band from the VODCA product3 averaged over the Amazon basin and the AR(1) signals obtained from it (as in Fig. 2c of Boulton et al.) alongside the AR(1) signals obtained from the radar data of Tao et al.
Fig. 2: Trends in AR(1) for the Amazon region VOD data from only the AMSR-E sensor, using the same preprocessing and methods as Boulton et al.

Data availability

Data measuring VOD from AMSR-E in the X- and C-bands can be found here: https://disc.gsfc.nasa.gov/datasets/LPRM_AMSRE_D_SOILM3_002/summary.

References

  1. Tao, S. et al. Little evidence that Amazonian rainforests are approaching a tipping point. Nat. Clim. Change https://doi.org/10.1038/s41558-023-01853-8 (2023).

  2. Boulton, C. A., Lenton, T. M. & Boers, N. Pronounced loss of Amazon rainforest resilience since the early 2000s. Nature Clim. Change 12, 271–278 (2022).

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  8. Espinoza, J. C. et al. The major floods in the Amazonas River and tributaries (Western Amazon Basin) during the 1970–2012 period: a focus on the 2012 flood. J. Hydrometeorol. 14, 1000–1008 (2013).

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Author information

Authors and Affiliations

  1. Global Systems Institute, University of Exeter, Exeter, UK

    Chris A. Boulton, Timothy M. Lenton & Niklas Boers

  2. Earth System Modelling, School of Engineering & Design, Technical University of Munich, Munich, Germany

    Niklas Boers

  3. Potsdam Institute for Climate Impact Research, Potsdam, Germany

    Niklas Boers

Authors
  1. Chris A. Boulton
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  2. Timothy M. Lenton
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  3. Niklas Boers
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Contributions

C.A.B. ran the analysis and all authors contributed to the writing of the manuscript.

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Correspondence to Chris A. Boulton.

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The authors declare no competing interests.

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Nature Climate Change thanks Bernardo Flores and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Boulton, C.A., Lenton, T.M. & Boers, N. Reply to: Little evidence that Amazonian rainforests are approaching a tipping point. Nat. Clim. Chang. 13, 1321–1323 (2023). https://doi.org/10.1038/s41558-023-01854-7

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