Aral Sea: its desiccated bed has released 748 million tonnes of CO₂ since 1960

Herz — World Desk · 16 July 2026 at 19:36 · 30s summary · 4 min read

What we know

A study published on July 16, 2026 in Science journal, led by Rafael Marcé of the Centro de Estudios Avanzados de Blanes — a laboratory affiliated with the CSIC, Spain's leading public research institution — quantifies the carbon footprint of the Aral Sea's desiccated bed. The team has worked for fifteen years on the carbon cycle in rivers and lakes undergoing desiccation.

Since 1960, this former water body has released 748 million tonnes of CO₂, equivalent to the combined annual emissions of Spain, France, and Belgium together.

An estimated 605 million tonnes of additional CO₂ could still be released from this site — more than double Spain's annual emissions.

The mechanism: from carbon sink to emission source

When a lake dries up, the disappearance of the water layer exposes sediments at the bottom to atmospheric oxygen. Microbial communities then degrade the accumulated organic matter and release CO₂ — transforming a carbon sink into an emission source.

The proposal: financing refilling through carbon credits

To stop these future emissions, the team proposes converting them into tradeable carbon credits — certificates representing a quantity of CO₂ not emitted, exchangeable on dedicated markets. Their value is estimated at between €3.1 and €15.8 billion, a wide range due to the absence of fixed pricing on these markets.

These revenues would finance the partial refilling of the Aral Sea and prevent most of the 605 million tonnes of CO₂ still at stake.

Context: the desiccation of a once-giant lake

The Aral Sea, located between Kazakhstan and Uzbekistan, was once the world's fourth-largest lake. It began shrinking in the early 1960s after the Soviet Union diverted its two main tributary rivers to irrigate cotton cultivation.

Today, less than 10% of its original area remains. The rest has become a salt desert.

Timeline

1. Early 1960s
   Soviet diversion of two rivers for cotton irrigation; Aral Sea desiccation begins.
2. 1960–2026
   748 million tonnes of CO₂ released by the desiccated bed, according to the study's measurements.
3. Rafael Marcé's team expedition to the site to measure the carbon footprint of the salt desert.