The global extent of the grassland biome and implications for the terrestrial carbon sink

MacDougall, A. S. and Vanzant, B. and Sulik, J. and Bagchi, S. and Naidu, D. and Muraina, T. O. and Seabloom, E. W. and Borer, E. T. and Wilfahrt, P. and Slette, I. and Hierro, J. L. and Pearson, D. E. and Abedi, M. and Akasaka, M. and Alberti, J. and Aleksanyan, A. and Amisu, A. A. and Anderson, T. M. and Arnillas, C. A. and Ayer, M. and Bakker, J. D. and Basant, S. and Basto, S. and Biederman, L. and Bloodworth, K. J. and Boscutti, F. and Boughton, E. H. and Bruschetti, C. M. and Buckley, H. L. and Buckley, Y. M. and Bugalho, M. N. and Caldeira, M. C. and Campetella, G. and Cannone, N. and Carbognani, M. and Carbutt, C. and Carniello, M. A. and Cervellini, M. and Chaudhary, T. and Chen, Q. and Clark, A. T. and Cousins, S. and Dalle Fratte, M. and Day, N. J. and Deák, B. and Dietrich, J. and Dixon, A. and Eisenhauer, N. and Elgersma, K. J. and Eren, O. and Eskelinen, A. and Estrada, C. and Fay, P. A. and Fayvush, G. and Flynn, K. C. and García Meza, D. and Gargano, D. and Gherardi, L. and Girkin, N. T. and González, L. and Graff, P. and Hagenberg, L. W. C. and Halbritter, A. H. and Havrilchak, N. A. and Herdoiza, N. and Hersch-Green, E. and Hopping, K. and Jentsch, A. and Jimoh, S. O. and Kerby, J. and Kirkman, K. and Knops, J. M. H. and Koerner, S. E. and Koltz, A. and Komatsu, K. J. and Koura, B. I. and Kruse, S. and Laanisto, L. and Lannes, L. S. and Li, W. and Liang, M. and Lkhagva, A. and López-Olmedo, L. and Lorenzo, P. and Lortie, C. J. and Loydi, A. and Luo, W. and Macek, P. and Malfasi, F. and Mariotte, P. and Martina, J. P. and Martínez-Blancas, A. and Martinson, H. and Martorell, C. and Meave, J. A. and Medina-Villar, S. and Mganga, K. Z. and Monsimet, J. and Nerlekar, A. N. and Niu, S. and Ohlert, T. and Oliveras Menor, I. and Oñatibia, G. R. and Ortega, Y. K. and Osborne, B. and Palpurina, S. and Pascual, J. and Pennings, S. C. and Pérez-García, E. and Peri, P. L. and Petit Bon, M. and Petraglia, A. and Pijcke, F. and Prober, S. M. and Quiroga, R. E. and Ramirez, J. I. and Reed, S. and Rosado, B. H. P. and Roscher, C. and Rowley, D. W. and Sereda, I. and Small, D. M. and Smith, N. G. and Song, Y. and Stevens, C. and Suarez Jimenez, L. E. and te Beest, M. and Tedder, M. and Terry, R. S. and Thornton, K. S. and Tian, D. and Titcomb, G. and Valkó, O. and ‘Ciska’ Veen, G. F. and Virtanen, R. and Welti, E. A. R. and Wheeler, G. R. and Wolf, A. A. and Wolff, P. and Young, A. L. and Young, H. S. and Zeglin, L. H. and Zhu, K. and Zong, S. and Siewert, M. B. (2026) The global extent of the grassland biome and implications for the terrestrial carbon sink. Nature Ecology and Evolution. ISSN 2397-334X

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Abstract

Land cover data are commonly used to model the terrestrial carbon (C) sink, yet these data have wide margins of error that significantly alter estimates of global C storage. Here we demonstrate this data vulnerability in grasslands, which are critical to C cycling but whose estimated distribution has varied by >50 million km2 (3.5–42% of the Earth’s terrestrial surface). Comparing multiple high-resolution land cover products with expertly annotated grassland data from six continents, we show sources of mapping error and discuss C implications based on 2023 United Nations (UN) FAO estimates. Past misidentification arose from inconsistent definitions on grassland identity and classification flaws especially relating to woody plant cover. Correcting these errors adjusted grassland coverage to 22.8% of the terrestrial land base (30.1 million km2), elevating UN projections of soil C stocks to 155.02 Pg (0–30 cm depth). These findings underscore the challenges of biome mapping for ecosystem accounting and policy, when lacking field-validated remotely sensed data.