A human-made desert exhales
The Aral Sea, once the fourth-largest lake on Earth, has lost over 90% of its volume since 1960. Soviet-era irrigation projects diverted the Amu Darya and Syr Darya rivers, the sea's two main inputs, to cultivate cotton and other crops in the desert. This diversion shrank the sea catastrophically, leaving behind a vast, dry seabed. By 2007, the sea was only 10% of its original size. This new, 40,000-square-kilometer landscape is called the Aralkum Desert, the youngest desert in the world.
The exposed lakebed is not inert; it is a massive source of atmospheric methane. Decades of accumulated organic matter—from plankton and other aquatic life—are now exposed to the air. As this material decomposes in the saline soil, microbes produce methane (CH4), a potent greenhouse gas. The remaining hypersaline water bodies of the Aral system also show high concentrations of dissolved methane due to the decomposition of organic material in anoxic, or oxygen-free, bottom layers. The estimated methane flux from the surface of the remaining Large Aral Sea is higher than that from many other lakes worldwide.
From carbon sink to carbon source
For millennia, the Aral Sea acted as a carbon sink, burying organic matter in its sediments. Now, its desiccation has reversed this function. The dried sediments are laden with salts and agricultural chemical residues like pesticides. Windstorms pick up this contaminated salt-dust and transport it hundreds, sometimes thousands, of kilometers. These dust storms, which can occur up to ten times a year, degrade soil fertility in surrounding regions and pose public health risks.
The local climate has also changed. Without the sea's moderating influence, winters have become colder and summers are hotter and drier. Dust emissions from the Aralkum Desert increased from 14 million to 27 million tons annually between 1984 and 2015. This dust can coat nearby glaciers, accelerating their melt and further straining the region's water resources. The combination of direct methane release and the wider climatic effects transforms the dead sea into a driver of environmental change. Restoration efforts, such as the Kok-Aral dam in the northern part of the sea, have brought back some water and fish to that section, but the vast southern basin continues to shrink and emit greenhouse gases.