Global terrestrial nitrogen fixation and its modification by agriculture

Carla R Reis Ely^{1

2}, Steven S Perakis³, Cory C Cleveland⁴, Duncan N L Menge⁵, Sasha C Reed⁶, Benton N Taylor⁷, Sarah A Batterman^{8

9

10}, Christopher M Clark¹¹, Timothy E Crews¹², Katherine A Dynarski⁴, Maga Gei¹³, Michael J Gundale¹⁴, David F Herridge¹⁵, Sarah E Jovan¹⁶, Sian Kou-Giesbrecht¹⁷, Mark B Peoples¹⁸, Johannes Piipponen¹⁹, Emilio Rodríguez-Caballero^{20

21}, Verity G Salmon²², Fiona M Soper²³, Anika P Staccone²⁴, Bettina Weber^{21

25}, Christopher A Williams²⁶, Nina Wurzburger²⁷

Affiliations

¹ Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, USA. carlargreis@gmail.com.
² Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA. carlargreis@gmail.com.
³ Forest and Rangeland Ecosystem Science Center, United States Geological Survey, Corvallis, OR, USA.
⁴ Department of Ecosystem and Conservation Sciences, W.A. Franke College of Forestry and Conservation, University of Montana, Missoula, MT, USA.
⁵ Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, NY, USA.
⁶ Southwest Biological Science Center, United States Geological Survey, Moab, UT, USA.
⁷ Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
⁸ Cary Institute of Ecosystem Studies, Millbrook, NY, USA.
⁹ School of Geography, University of Leeds, Leeds, UK.
¹⁰ Smithsonian Tropical Research Institute, Smithsonian Institution, Ancon, Panama.
¹¹ Office of Research and Development, US Environmental Protection Agency, Washington DC, USA.
¹² The Land Institute, Salina, KS, USA.
¹³ Association for Tropical Biology and Conservation, Minneapolis, MN, USA.
¹⁴ Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umea, Sweden.
¹⁵ School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia.
¹⁶ PNW Research Station, USDA Forest Service, Portland, OR, USA.
¹⁷ Department of Earth and Environmental Sciences, Dalhousie University, Halifax, Nova Scotia, Canada.
¹⁸ CSIRO Agriculture and Food, CSIRO, Canberra, Australian Capital Territory, Australia.
¹⁹ Water and Development Research Group, Aalto University, Espoo, Finland.
²⁰ Centro de Investigación de Colecciones Científicas de la Universidad de Almería (CECOUAL) y Departamento de Agronomía, Universidad de Almería, Almería, Spain.
²¹ Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany.
²² Environmental Science Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
²³ Department of Biology and School of the Environment, McGill University, Montreal, Quebec, Canada.
²⁴ Earthshot Labs, Sebastopol, CA, USA.
²⁵ Division of Plant Sciences, Institute for Biology, University of Graz, Graz, Austria.
²⁶ Graduate School of Geography, Clark University, Worcester, MA, USA.
²⁷ Odum School of Ecology, University of Georgia, Athens, GA, USA.

PMID: 40670639
PMCID: PMC12506932 (available on 2026-07-16)
DOI: 10.1038/s41586-025-09201-w

Global terrestrial nitrogen fixation and its modification by agriculture

Carla R Reis Ely et al. Nature. 2025 Jul.

. 2025 Jul;643(8072):705-711.

doi: 10.1038/s41586-025-09201-w. Epub 2025 Jul 16.

Authors

Affiliations

¹ Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, USA. carlargreis@gmail.com.
² Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA. carlargreis@gmail.com.
³ Forest and Rangeland Ecosystem Science Center, United States Geological Survey, Corvallis, OR, USA.
⁴ Department of Ecosystem and Conservation Sciences, W.A. Franke College of Forestry and Conservation, University of Montana, Missoula, MT, USA.
⁵ Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, NY, USA.
⁶ Southwest Biological Science Center, United States Geological Survey, Moab, UT, USA.
⁷ Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
⁸ Cary Institute of Ecosystem Studies, Millbrook, NY, USA.
⁹ School of Geography, University of Leeds, Leeds, UK.
¹⁰ Smithsonian Tropical Research Institute, Smithsonian Institution, Ancon, Panama.
¹¹ Office of Research and Development, US Environmental Protection Agency, Washington DC, USA.
¹² The Land Institute, Salina, KS, USA.
¹³ Association for Tropical Biology and Conservation, Minneapolis, MN, USA.
¹⁴ Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umea, Sweden.
¹⁵ School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia.
¹⁶ PNW Research Station, USDA Forest Service, Portland, OR, USA.
¹⁷ Department of Earth and Environmental Sciences, Dalhousie University, Halifax, Nova Scotia, Canada.
¹⁸ CSIRO Agriculture and Food, CSIRO, Canberra, Australian Capital Territory, Australia.
¹⁹ Water and Development Research Group, Aalto University, Espoo, Finland.
²⁰ Centro de Investigación de Colecciones Científicas de la Universidad de Almería (CECOUAL) y Departamento de Agronomía, Universidad de Almería, Almería, Spain.
²¹ Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany.
²² Environmental Science Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
²³ Department of Biology and School of the Environment, McGill University, Montreal, Quebec, Canada.
²⁴ Earthshot Labs, Sebastopol, CA, USA.
²⁵ Division of Plant Sciences, Institute for Biology, University of Graz, Graz, Austria.
²⁶ Graduate School of Geography, Clark University, Worcester, MA, USA.
²⁷ Odum School of Ecology, University of Georgia, Athens, GA, USA.

PMID: 40670639
PMCID: PMC12506932 (available on 2026-07-16)
DOI: 10.1038/s41586-025-09201-w

Abstract

Biological nitrogen fixation (BNF) is the largest natural source of new nitrogen (N) that supports terrestrial productivity^1,2, yet estimates of global terrestrial BNF remain highly uncertain^3,4. 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^-1, than previous empirical bottom-up estimates^3,4, 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^-1. 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^5,6, with implications for proposed safe operating limits for N use^7,8.

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Conflict of interest statement

Competing interests: The authors declare no competing interests.

References

Main references

1. Houlton BZ, Morford SL & Dahlgren RA Convergent evidence for widespread rock nitrogen sources in Earth’s surface environment. Science 360, 58–62 (2018). - PubMed
1. Fowler D et al. The global nitrogen cycle in the twenty-first century. Philos T R Soc B 368, (2013). - PMC - PubMed
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1. Kou-Giesbrecht S et al. Evaluating nitrogen cycling in terrestrial biosphere models: a disconnect between the carbon and nitrogen cycles. Earth Syst Dynam 14, 767–795 (2023).

Methods References

1. Soper FM et al. A roadmap for sampling and scaling biological nitrogen fixation in terrestrial ecosystems. Methods Ecol Evol 12, 1122–1137 (2021).
1. Winbourne JB et al. A new framework for evaluating estimates of symbiotic nitrogen fixation in forests. Am Nat 192, 618–629 (2018). - PubMed
1. Abatzoglou JT, Dobrowski SZ, Parks SA & Hegewisch KC TerraClimate, a high-resolution global dataset of monthly climate and climatic water balance from 1958–2015. Sci Data 5, (2018). - PMC - PubMed
1. Friedl MA & Sulla-Menashe D MCD12Q1 MODIS/Terra+Aqua Land Cover Type Yearly L3 Global 500m SIN Grid V006 [Data set]. NASA EOSDIS Land Processes Distributed Active Archive Center. 10.5067/MODIS/MCD12Q1.006 (2019). - DOI
1. Cummings SP, Humphry DR, Santos SR, Andrews M & James EK The potential and pitfalls of exploiting nitrogen fixing bacteria in agricultural soils as a substitute for inorganic fertiliser. Environ Biotechnol 2, 1–10 (2006).

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Global terrestrial nitrogen fixation and its modification by agriculture

Affiliations

Global terrestrial nitrogen fixation and its modification by agriculture

Authors

Affiliations

Abstract

Conflict of interest statement

References

Main references

Methods References

MeSH terms

Substances

Grants and funding

LinkOut - more resources

Full Text Sources

Miscellaneous