Drying of the Aral Sea reshapes the anthropogenic carbon inventory of Central Asia.

Lakes store large quantities of carbon in their sediments, contributing to climate regulation. Yet the fate of this carbon after lake desiccation remains unclear. Using a space-for-time substitution approach, combining sediment cores, carbon dioxide flux measurements, and remote sensing, we quantified organic carbon losses from the world's largest desiccated lake, the Aral Sea. Since 1960, exposed lake bed sediments have released 204 ± 53 teragrams of carbon (Tg C), with vegetation growth offsetting less than 1%. Incorporating these emissions alters the regional carbon budget, transforming the Aral Sea basin from a presumed land-use-change carbon sink into a net source. Reflooding the sea could prevent an additional 165 ± 13 Tg C release, reframing restoration not only as an ecological and humanitarian imperative but also as a climate mitigation opportunity.