The Aral Sea, once the fourth largest inland lake on Earth, has released about 748 million metric tons of carbon dioxide since 1960 as it dried up, according to a study published in Science. Researchers sampled lakebed sediment along a timeline of drying and found that exposed organic carbon turns from a long-term sink into a source. Windblown dust from the dried bed accounted for nearly a fifth of the total emissions, a pathway often missing from lake carbon budgets. The study estimates another 605 million metric tons of CO2 could still be released, but that also represents carbon that could stay locked in the ground if water returns. The authors put the value of that avoided release at around $18 billion in carbon credits. Similar risks apply to Lake Chad, the Caspian Sea, the Salton Sea, and the Great Salt Lake, which means drying inland waters are a growing and undercounted part of the global carbon cycle.
