Age, extent and carbon storage of the central Congo Basin peatland complex (original) (raw)

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Acknowledgements

We thank the Wildlife Conservation Society Congo Programme for logistical support and the villages that hosted our fieldwork: Bokatola, Bolembe, Bondoki, Bondzale, Ekolongouma, Ekondzo, Itanga, Mbala and Moungouma. We thank F. Twagirashyaka, T. F. Moussavou, P. Telfer, A. Pokempner, J. J. Loumeto and A. Rahïm (logistics); R. Mbongo, P. Abia (deceased), T. Angoni, C. Bitene, J. B. Bobetolo, C. Bonguento, J. Dibeka, B. Elongo, C. Fatty, M. Ismael, M. Iwango, G. Makweka, L. Mandomba, C. Miyeba, A. Mobembe, E. B. Moniobo, F. Mosibikondo, F. Mouapeta, G. Ngongo, G. Nsengue, L. Nzambi and J. Saboa (field assistance); M. Gilpin, D. Ashley and R. Gasior (laboratory assistance); D. Quincy (remote sensing and GIS support); D. Harris, J. M. Moutsambote (plant identification); P. Gulliver (radiocarbon analyses); F. Draper (access to Peruvian data); and T. Kelly and D. Young (discussions). The work was funded by Natural Environment Research Council (CASE award to S.L.L. and G.C.D.; fellowship to E.M.; NERC Radiocarbon Facility NRCF010001 (alloc. no. 1688.0313 and 1797.0414) to I.T.L., S.L.L. and G.C.D.); Wildlife Conservation Society-Congo (to G.C.D.), the Royal Society (to S.L.L.), Philip Leverhulme Prize (to S.L.L.), and the European Union (FP7, GEOCARBON to S.L.L.; ERC T-FORCES to S.L.L.). JAXA, METI, USGS, NASA and OSFAC are acknowledged for collecting and/or processing remote sensing data.

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Author notes

  1. Greta C. Dargie and Simon L. Lewis: These authors contributed equally to this work.

Authors and Affiliations

  1. School of Geography, University of Leeds, Leeds, LS2 9JT, UK
    Greta C. Dargie & Simon L. Lewis
  2. Department of Geography, University College London, London, WC1E 6BT, UK
    Greta C. Dargie & Simon L. Lewis
  3. Department of Geography and Sustainable Development, University of St Andrews, St Andrews, KY16 9AL, UK
    Ian T. Lawson
  4. School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UK
    Edward T. A. Mitchard
  5. Department of Geography, University of Leicester, Leicester, LE1 7RH, UK
    Susan E. Page
  6. Faculté des Sciences et Techniques, Université Marien Ngouabi, Brazzaville, Republic of the Congo
    Yannick E. Bocko & Suspense A. Ifo

Authors

  1. Greta C. Dargie
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  2. Simon L. Lewis
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  3. Ian T. Lawson
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  4. Edward T. A. Mitchard
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  5. Susan E. Page
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  6. Yannick E. Bocko
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  7. Suspense A. Ifo
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Contributions

S.L.L. conceived the study. G.C.D., S.L.L., I.T.L., S.A.I and S.E.P. developed the study. G.C.D. collected most of the data, assisted by B.E.Y., S.L.L. and I.T.L. Laboratory analyses were performed by G.C.D. G.C.D. and E.T.A.M. analysed the remotely sensed data. G.C.D., S.L.L., I.T.L., E.T.A.M. and S.E.P. interpreted the data. G.C.D. and S.L.L. wrote the paper, with input from all co-authors.

Corresponding author

Correspondence toGreta C. Dargie.

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The authors declare no competing financial interests.

Additional information

Reviewer Information Nature thanks J. Chambers, L. Fatoyinbo and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Figure 1 Peatland water table time-series data.

a, b, Time series of water-table levels for the Ekolongouma (a) and Itanga (b) transects for the time period March 2013 to May 2014 (black, blue and red lines indicate different sample locations along the transects). c, d, Time series of water-table levels for the wet-season month of October 2013 for the Ekolongouma (c) and Itanga (d) transects, when river-caused flood events are more likely (left-hand axis; black, blue and red lines), and daily TRMM rainfall estimates (right-hand axis; purple lines). No obvious flood waves are seen. e, Relationship between the summed monthly cumulative increase in water table (CIWT) from 10 pressure transducers (Itanga, Ekolongouma, Bonzale and Bondoki transects), for months in which CIWT > 0, and summed monthly rainfall estimates for the same months from TRMM (best-fitting line: y = 0.959_x_ − 133, _R_2 = 0.90, P < 0.001). Months during which the water table was not always above the peatland surface (CIWT ≤ 0) were excluded from the analysis, owing to large changes in the water table that obscure the relationship between water table and water input. Data from 10 pressure transducers are included, because two transducers had no months during which the water table was consistently above the peat surface.

Extended Data Figure 2 Spatial distribution of the ground-truth points across the Cuvette Centrale.

Main panel, ALOS PALSAR imagery of the Cuvette Centrale area and the spatial distribution of the ground-truth points (crosses for GPS, circles for Google Earth derived points) that were used as test and training data in the 1,000 runs of the maximum likelihood classifications used to estimate regional peat extent. The black boxes correspond to the other panels: a, the main study region; b, c, two regions within DRC where GPS ground-truth points were also obtained.

Extended Data Figure 3 Relationship between estimates of peat depth using the field-pole method and those using peat cores followed by laboratory analysis, and the relationship between corrected peat depth and total peat carbon stocks.

a, Relationship between peat depth (in m) estimated using a metal pole (rapid protocol) and estimated using coring and laboratory analysis (full protocol); LOI, loss-on-ignition; best-fitting line: y = 0.888_x_ − 34.8, _R_2 = 0.97, P < 0.001, where y is cored peat depth and x is pole peat depth. The organic matter content of the core must be ≥65% to be classified as peat. Soft carbon-rich material that is <65% organic matter is captured using the rapid protocol, which lies beneath peat using our definition, but above the more typical mineral soil. b, Relationship between core depth (in m) and total carbon stocks (in Mg C ha−1) for cores from the Cuvette Centrale (best-fitting line: carbon stocks = 1,374 + 2,425log10(total core depth), _R_2 = 0.89, P < 0.0001).

Extended Data Figure 4 Distribution of peatland carbon stock estimates.

Estimated carbon stocks from 100,000 resamples of peatland area, peat depth and per-unit-area carbon storage. Median, 30.6 Pg C; mean, 29.8 Pg C; 95% CI, 6.3–46.8 Pg C.

Extended Data Table 1 Description of remote-sensing products used to identify field sites in the Cuvette Centrale

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Extended Data Table 2 Radiocarbon dates from nine peat cores

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Extended Data Table 3 Average peat accumulation rate and long-term rate of carbon accumulation (LORCA) for nine radiocarbon-dated peat cores

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Extended Data Table 4 Vegetation classes encountered in the field, and their associations (or not) with peat

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Extended Data Table 5 Remote-sensing products used in the maximum likelihood classification to map peatland extent within the Cuvette Centrale

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Extended Data Table 6 Land-cover classes, ground-truth sample sizes, estimated extent of each class from 1,000 maximum likelihood model runs, and producer’s, user’s and overall accuracy of the classifications

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Dargie, G., Lewis, S., Lawson, I. et al. Age, extent and carbon storage of the central Congo Basin peatland complex.Nature 542, 86–90 (2017). https://doi.org/10.1038/nature21048

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