Old carbon routed from land to the atmosphere by global river systems

Dean, Joshua F. ORCID: https://orcid.org/0000-0001-9058-7076; Coxon, Gemma ORCID: https://orcid.org/0000-0002-8837-460X; Zheng, Yanchen; Bishop, Jack; Garnett, Mark H. ORCID: https://orcid.org/0000-0001-6486-2126; Bastviken, David ORCID: https://orcid.org/0000-0003-0038-2152; Galy, Valier ORCID: https://orcid.org/0000-0003-0385-8443; Spencer, Robert G.M. ORCID: https://orcid.org/0000-0003-0777-0748; Tank, Suzanne E. ORCID: https://orcid.org/0000-0002-5371-6577; Tipper, Edward T. ORCID: https://orcid.org/0000-0003-3540-3558; Vonk, Jorien E. ORCID: https://orcid.org/0000-0002-1206-5878; Wallin, Marcus B. ORCID: https://orcid.org/0000-0002-3082-8728; Zhang, Liwei ORCID: https://orcid.org/0000-0002-1610-2816; Evans, Chris D. ORCID: https://orcid.org/0000-0002-7052-354X; Hilton, Robert G. ORCID: https://orcid.org/0000-0002-0499-3332. 2025 Old carbon routed from land to the atmosphere by global river systems. Nature, 642 (8066). 105-111. 10.1038/s41586-025-09023-w

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Abstract/Summary

Rivers and streams are an important pathway in the global carbon cycle, releasing carbon dioxide (CO 2 ) and methane (CH 4 ) from their water surfaces to the atmosphere 1,2 . Until now, CO 2 and CH 4 emitted from rivers were thought to be predominantly derived from recent (sub-decadal) biomass production and, thus, part of ecosystem respiration 3–6 . Here we combine new and published measurements to create a global database of the radiocarbon content of river dissolved inorganic carbon (DIC), CO 2 and CH 4 . Isotopic mass balance of our database suggests that 59 ± 17% of global river CO 2 emissions are derived from old carbon (millennial or older), the release of which is linked to river catchment lithology and biome. This previously unrecognized release of old, pre-industrial-aged carbon to the atmosphere from long-term soil, sediment and geologic carbon stores through lateral hydrological routing equates to 1.2 ± 0.3 Pg C year −1 , similar in magnitude to terrestrial net ecosystem exchange. A consequence of this flux is a greater than expected net loss of carbon from aged organic matter stores on land. This requires a reassessment of the fate of anthropogenic carbon in terrestrial systems and in global carbon cycle budgets and models.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1038/s41586-025-09023-w
UKCEH and CEH Sections/Science Areas:	Land-Atmosphere Interactions (2025-)
ISSN:	0028-0836
Additional Information:	Open Access paper - full text available via Official URL link.
Additional Keywords:	carbon cycle, hydrology
NORA Subject Terms:	Hydrology Atmospheric Sciences
Related URLs:	Dataset Code
Date made live:	12 Jun 2025 10:59 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539573

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