According to a study published in the journal Science on July 16, 2026, and led by the Center for Advanced Studies of Blanes in Spain, the exposed dry-bed sediments of the Aral Sea in Central Asia have released 748 megatons of carbon dioxide since the 1960s, turning a historic environmental disaster into a significant localized climate driver.
The Soviet Diversion and the Collapse of the Fourth-Largest Lake
Once holding the title of the fourth-largest lake in the world, the Aral Sea sits in Central Asia spanning the borders of Kazakhstan and Uzbekistan. In the span of roughly half a century, the inland saltwater body lost about 90% of its total volume. Its surface area and overall volume plummeted by 75% and 90% respectively over sixty years.
This collapse stems directly from Soviet-era agricultural policies. The former Soviet Union deliberately diverted the powerful Amudarya and Syrdarya rivers away from the basin. The goal was massive agricultural production, specifically wheat and cotton grown inside the surrounding desert. Today, the basin is fractured into two distinct water bodies: the Lesser Aral Sea trapped by a dam in the north, and the critically dying Greater Aral Sea in the south.
How Exposed Lake Sediments Vent Carbon
Inland water bodies operate as core regulators of the global carbon cycle. Microscopic algae and aquatic plants naturally capture atmospheric carbon, which ultimately settles and stores over long periods within lake-bed sediments as organic matter. However, dropping water levels disrupt this storage mechanism completely.
When engineering shifts or climate pressures expose those oxygen-rich sédiments directly to the atmosphere, the organic matter undergoes rapid aerobic decomposition. This biological and chemical breakdown converts stored carbon directly into vented CO2 gas. Furthermore, the researchers discovered that roughly one-fifth of the total carbon is not released directly as a gas from the soil. Instead, high-velocity sandstorms sweep up carbon-laden dust particles and transport them across the region.
The study mapped out a precise timeline for this atmospheric venting. During the first fifteen years of the regression, half of the total sediment-bound CO2 escaped into the atmosphere. As the pool of easily accessible organic carbon depleted, the emission flux naturally began to slow down. Meanwhile, active regional revegetation efforts—such as planting saxaul trees known scientifically as Haloxylon ammodendron—currently offset less than 1% of total carbon losses.
Locking Remaining Carbon Through Targeted Rehabilitation
Despite decades of degradation, the ecosystem retains remaining reserves. Subsurface sediments that have not finished drying completely still trap an estimated 605 megatons of carbon dioxide. Without direct conservation intervention, this remaining carbon will inevitably escape into the atmosphere.
To prevent further atmospheric loading, the study authors called for the ecological rehabilitation of the Aral Sea basin. Proposed interventions include partial water restoration or targeted rehydration projects designed to lock the remaining carbon safely back into wet sediment layers. Economic models suggest that restoring the region could generate between 3,6 (limite basse) et 18 milliards de dollars (limite haute) in tradeable carbon credits on international voluntary markets. Under these market mechanisms, a single avoided metric ton of CO2 equates to an avoided carbon credit.
Funding for such an ambitious rehabilitation project would likely bypass the national budgets of Kazakhstan and Uzbekistan. Instead, researchers propose that international private sectors—including aviation, hydrocarbon, tech, and finance giants seeking credible offsets for their own operational footprints—could purchase these voluntary credits to finance the restoration.
