MacDougall A. S., Vanzant B., Sulik J., Bagchi S., Naidu D., Muraina T. O., Seabloom E. W., Borer E. T., Wilfahrt P., Slette I., Hierro J. L., Pearson D. E., Mariotte P., Siewert M. B.
The global extent of the grassland biome and implications for the terrestrial carbon sink.
Land cover data are commonly used to model the terrestrial carbon (C) sink, yet these data have wide margins of error that signi!cantly 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 misidenti!cation arose from inconsistent de!nitions on grassland identity and classi!cation #aws 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 !ndings underscore the challenges of biome mapping for ecosystem accounting and policy, when lacking !eld-validated remotely sensed data.