The shrinking Aral Sea has released an estimated 825 million tonnes (748 million metric tonnes) of carbon dioxide since 1960, transforming what was once one of the world’s largest inland lakes into a major source of greenhouse gas emissions, according to a study published in the journal Science.
Researchers found that as the Aral Sea dried up due to large scale river diversions for irrigation, its exposed lake bed began releasing carbon that had remained trapped in sediments for centuries. Around half of these emissions occurred within the first 15 years after each section of the lake bed dried.
The study estimates that the dried lake bed has emitted carbon dioxide equivalent to nearly three times Spain’s annual emissions, while newly established vegetation has offset less than 1% of the released carbon.
Scientists also discovered that nearly 20% of the carbon escaped as wind blown dust instead of carbon dioxide gas, spreading carbon rich, salt laden particles across Central Asia.
Despite the large losses, researchers estimate that about 667 million tonnes of carbon dioxide remain locked beneath sediments that are still submerged. They say restoring water to parts of the Aral Sea could prevent these remaining carbon stores from being released into the atmosphere.
The researchers warn that drying lakes around the world including the Great Salt Lake in the United States, Lake Chad in Africa, and the Salton Sea in California could become significant but overlooked sources of greenhouse gas emissions, highlighting the need to include dried lake beds in future climate accounting.