Global terrestrial nitrogen fixation and its modification by agriculture

Biological nitrogen fixation (BNF) is the largest natural source of new nitrogen (N) that supports terrestrial productivity<sup>1,2</sup>, yet estimates of global terrestrial BNF remain highly uncertain<sup>3,4</sup>. Here we show that this uncertainty is partly because of sampling bias, as field BNF measurements in natural terrestrial ecosystems occur where N fixers are 17 times more prevalent than their mean abundances worldwide. To correct this bias, we develop new estimates of global terrestrial BNF by upscaling field BNF measurements using spatially explicit abundances of all major biogeochemical N-fixing niches. We find that natural biomes sustain lower BNF, 65 (52-77) Tg N yr<sup>-1</sup>, than previous empirical bottom-up estimates<sup>3,4</sup>, with most BNF occurring in tropical forests and drylands. We also find high agricultural BNF in croplands and cultivated pastures, 56 (54-58) Tg N yr<sup>-1</sup>. Agricultural BNF has increased terrestrial BNF by 64% and total terrestrial N inputs from all sources by 60% over pre-industrial levels. Our results indicate that BNF may impose stronger constraints on the carbon sink in natural terrestrial biomes and represent a larger source of agricultural N than is generally considered in analyses of the global N cycle<sup>5,6</sup>, with implications for proposed safe operating limits for N use<sup>7,8</sup>.

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Publication Details

Journal
Nature
Published
2025-07-16
DOI
https://doi.org/10.1038/s41586-025-09201-w
Citations
24
Primary Topic
Soil Carbon and Nitrogen Dynamics
Type
article
Field-Weighted Citation Impact
28.46
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article

Global terrestrial nitrogen fixation and its modification by agriculture

Johannes Piipponen, Duncan N. L. Menge, Cory C. Cleveland, Verity Salmon et al.
24 citations
Nature
Soil Carbon and Nitrogen Dynamics
28.46
article

Global terrestrial nitrogen fixation and its modification by agriculture

Johannes Piipponen, Duncan N. L. Menge, Cory C. Cleveland, Verity Salmon, C. A. Williams, Steven S. Perakis, Maga Gei, Michael J. Gundale, Mark B. Peoples, Bettina Weber, Christopher M. Clark, Sasha C. Reed, Sarah Jovan, Katherine A. Dynarski, Benton N. Taylor, Nina Wurzburger, Anika P. Staccone, Sarah A. Batterman, Carla Roberta Gonçalves Reis, Sian Kou‐Giesbrecht, Fiona M. Soper, Emilio Rodríguez‐Caballero, Timothy E. Crews, D. F. Herridge
article en
24 citations

Abstract

Biological nitrogen fixation (BNF) is the largest natural source of new nitrogen (N) that supports terrestrial productivity<sup>1,2</sup>, yet estimates of global terrestrial BNF remain highly uncertain<sup>3,4</sup>. Here we show that this uncertainty is partly because of sampling bias, as field BNF measurements in natural terrestrial ecosystems occur where N fixers are 17 times more prevalent than their mean abundances worldwide. To correct this bias, we develop new estimates of global terrestrial BNF by upscaling field BNF measurements using spatially explicit abundances of all major biogeochemical N-fixing niches. We find that natural biomes sustain lower BNF, 65 (52-77) Tg N yr<sup>-1</sup>, than previous empirical bottom-up estimates<sup>3,4</sup>, with most BNF occurring in tropical forests and drylands. We also find high agricultural BNF in croplands and cultivated pastures, 56 (54-58) Tg N yr<sup>-1</sup>. Agricultural BNF has increased terrestrial BNF by 64% and total terrestrial N inputs from all sources by 60% over pre-industrial levels. Our results indicate that BNF may impose stronger constraints on the carbon sink in natural terrestrial biomes and represent a larger source of agricultural N than is generally considered in analyses of the global N cycle<sup>5,6</sup>, with implications for proposed safe operating limits for N use<sup>7,8</sup>.

NatureVol. 643(8072)
Oak Ridge Associated Universities (US), Smithsonian Tropical Research Institute (PA), United States Geological Survey (US), Oak Ridge National Laboratory (US), Commonwealth Scientific and Industrial Research Organisation (AU), Dalhousie University (CA), Environmental Protection Agency (US), Clark University (US), University of Leeds (GB), Oregon State University (US), US Forest Service (US), Harvard University (US), University of Graz (AT), University of Georgia (US), Minnesota Medical Association (US), Swedish University of Agricultural Sciences (SE), Cary Institute of Ecosystem Studies (US), The Land Institute (US), Advanced MRI Technologies (United States) (US), Max Planck Institute for Chemistry (DE), McGill University (CA), University of Almería (ES), University of Montana (US), Columbia University (US), University of New England (AU), Aalto University (FI)
Zero hunger
Openalex Percentile: Top 0%
Soil Carbon and Nitrogen Dynamics
28.46
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