Enric Gomis, Simone Strydom, Nicole R. Foster, Diana I. Montemayor, Miguel Á. Mateo, Eduard Serrano, Karina Inostroza, Roisin McCallum, Anna Lafratta, Chanelle L. Webster, Caitlyn M. O’Dea, Nicole E. Said, Natasha Dunham, Rachele Bernasconi, Axel Werner, Federico Vitelli, Viena Puigcorbé, Alexandra D’Cruz, Cristian Salinas, Kathryn McMahon, Glenn A. Hyndes, Paul S. Lavery, Albert Pessarodona, Carlos M. Duarte, Óscar Serrano
Seagrass meadows play a key role in the global carbon cycle through storing carbon in their biomass and soils. However, the lack of global assessments of carbon stocks in seagrass biomass and net primary production (NPP) limits our understanding of their role in the carbon cycle. Here, we provide global estimates of biomass carbon stocks and NPP encompassing seagrasses with different life-history strategies, across bioregions and 66 countries. Seagrass meadows show up to 800-fold differences in biomass across different life-history strategies and bioregions (mean ± SE; 1551 ± 40 kg C ha−1), whereas seagrass NPP (5833 ± 557 kg C ha−1 yr−1) ranks among the highest within photosynthetic ecosystems. We estimate seagrass biomass carbon stocks at 24–40 Tg C and NPP at 83–137 Tg C yr−1 within 160,387 to 266,500 km2 of global seagrass extent. This study showcases the role of seagrasses in the global carbon cycle and provides the basis for their inclusion in carbon crediting schemes towards implementing conservation actions for climate change mitigation. Seagrass meadows store 24–40 million tons of carbon and fix 83–137 million tons of carbon annually in their biomass, ranking among the most productive ecosystems on Earth. Seagrass conservation can contribute to climate change mitigation.