Abstract

A substantial amount of the atmospheric carbon taken up on land through photosynthesis and chemical weathering is transported laterally along the aquatic continuum from upland terrestrial ecosystems to the ocean. So far, global carbon budget estimates have implicitly assumed that the transformation and lateral transport of carbon along this aquatic continuum has remained unchanged since pre-industrial times. A synthesis of published work reveals the magnitude of present-day lateral carbon fluxes from land to ocean, and the extent to which human activities have altered these fluxes. We show that anthropogenic perturbation may have increased the flux of carbon to inland waters by as much as 1.0 Pg C yr−1 since pre-industrial times, mainly owing to enhanced carbon export from soils. Most of this additional carbon input to upstream rivers is either emitted back to the atmosphere as carbon dioxide (0.4 Pg C yr−1) or sequestered in sediments (0.5 Pg C yr−1) along the continuum of freshwater bodies, estuaries and coastal waters, leaving only a perturbation carbon input of 0.1 Pg C yr−1 to the open ocean. According to our analysis, terrestrial ecosystems store 0.9 Pg C yr−1 at present, which is in agreement with results from forest inventories but significantly differs from the figure of 1.5 Pg C yr−1 previously estimated when ignoring changes in lateral carbon fluxes. We suggest that carbon fluxes along the land–ocean aquatic continuum need to be included in global carbon dioxide budgets.

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Acknowledgements

This paper is the outcome of the workshop 'Exploring knowledge gaps along the global carbon route: a hitchhiker's guide for a boundless cycle' held in Eprave, Belgium, in November 2011. The authors would like to thank S. Bonneville, L. Chou, P. Cox, H. Durr, T. Eglinton, K. Fleischer, J. Kaplan, T. Kleinen, D. Dan Li, A. Mouchet, H. Nick, C. Pallud, C. Prentice, D. Schimel, M. Serrano, J-L. Tison, P. Van Cappellen, C. Volta and J. Zhou for their input during the workshop. The workshop was officially endorsed by the Global Carbon Project (GCP) and by the Analysis, Integration and Modeling of the Earth System (AIMES) of the International Geosphere-Biosphere Programme (IGBP) and received financial support from the government of the Brussels-Capital region (Innoviris — Brains Back to Brussels award to P.R.), the Walloon Agency for Air and Climate (AWAC), the Fonds National de la Recherche Scientifique of Belgium (FNRS), The Belgian Federal Science Policy Office (BELSPO), the Université Libre de Bruxelles (Belgium), the Netherlands Organization for Scientific Research (NWO), the King Abdullah University of Science and Technology (KAUST) Center-in-Development Award to Utrecht University (The Netherlands), the University of Waterloo (Canada) and the University of Exeter (UK). The research leading to these results received funding from the European Union's Seventh Framework Program (FP7/2007–2013) under grant agreement number 283080, project GEOCARBON.

Author information

Affiliations

  1. Department of Earth and Environmental Sciences, CP160/02, Université Libre de Bruxelles, 1050 Bruxelles, Belgium

    • Pierre Regnier
    • , Goulven G. Laruelle
    • , Ronny Lauerwald
    •  & Nicolas Goossens
  2. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK

    • Pierre Friedlingstein
  3. Laboratoire des Sciences du Climat et l'Environnement, 91190 Gif-sur-Yvette, France

    • Philippe Ciais
    •  & Sebastiaan Luyssaert
  4. Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawai'i at Mãnoa, Honolulu, Hawaii 96822, USA

    • Fred T. Mackenzie
  5. Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, ETH Zürich, 8092 Zurich, Switzerland

    • Nicolas Gruber
  6. Departement Biologie, Universiteit Antwerpen, 2160 Wilrijk, Belgium

    • Ivan A. Janssens
  7. Institute for Biogeochemistry and Marine Chemistry, KlimaCampus, D-20146 Hamburg, Germany

    • Ronny Lauerwald
    •  & Jens Hartmann
  8. Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0202, USA

    • Andreas J. Andersson
  9. School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK

    • Sandra Arndt
  10. Department of Marine Sciences, University of North Carolina, Chapel Hill, North Carolina 27599, USA

    • Carol Arnosti
  11. University of Liège, Chemical Oceanography Unit, Institut de Physique (B5), B-4000 Liège, Belgium

    • Alberto V. Borges
  12. GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Wischhofstraβe 1-3, 24148 Kiel, Germany

    • Andrew W. Dale
  13. Department of Geography, University of Exeter, Exeter EX4 4RJ, UK

    • Angela Gallego-Sala
  14. Géosciences Environnement Toulouse, Centre National de la Recherche Scientifique, Observatoire Midi-Pyrénées, Université Toulouse III, 31400 Toulouse, France

    • Yves Goddéris
  15. Geophysical Institute, University of Bergen, N-5007 Bergen, Norway

    • Christoph Heinze
  16. Bjerknes Centre for Climate Research, N-5007 Bergen, Norway

    • Christoph Heinze
  17. Uni Bjerknes Centre, Uni Research, N-5007 Bergen, Norway

    • Christoph Heinze
  18. Max Planck Institute for Meteorology, 20146 Hamburg, Germany

    • Tatiana Ilyina
  19. Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, Bern CH-3012, Switzerland

    • Fortunat Joos
    •  & Renato Spahni
  20. Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA

    • Douglas E. LaRowe
  21. Agroscope Research Station ART, Reckenholzstrasse 191, 8046 Zurich, Switzerland

    • Jens Leifeld
  22. Royal Netherlands Institute of Sea Research, 4401 NT Yerseke, The Netherlands

    • Filip J. R. Meysman
  23. Department of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, 1050 Brussel, Belgium

    • Filip J. R. Meysman
  24. Laboratoire de Physique Atmosphérique et Planétaire, Université de Liège, B-4000 Liège, Belgium

    • Guy Munhoven
  25. Yale School of Forestry and Environmental Studies, New Haven, Connecticut 06511, USA

    • Peter A. Raymond
  26. School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK

    • Parvadha Suntharalingam
  27. Department of Environmental Microbiology, Helmholtz Centre for Environmental Research, Leipzig 04318, Germany

    • Martin Thullner

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Contributions

P.R. and P.F. initiated the Eprave workshop that led to this paper. P.R. coordinated and participated at all stages of the conception and writing of the paper. P.F., P.C., F.T.M. and N.G. were central to the conception of the paper and to the writing of the manuscript. I.A.J. proposed the overall design of Fig. 3. G.G.L. and R.L. produced Fig. 2, using the GloRiCh database for inland waters assembled by J. Hartmann and co-workers. S.L. took a leading role in the quantification of the terrestrial ecosystem budget. All other authors contributed to specific aspects of the budget analysis and commented on various versions of the manuscript. F.T.M. was instrumental to the genesis of this paper through his pioneering work in the field.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Pierre Regnier.

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https://doi.org/10.1038/ngeo1830

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