When lakes decline, can they recover?

The world's largest lakes could significantly shrink over the coming century, threatening ecosystems and impacting roughly a quarter of the global population. The Caspian Sea, despite its name, is the largest inland body of water and has experienced a rapid decline in surface area since the 1990s due to dam construction and increased evaporation from higher temperatures.

Even a 10-meter drop could leave much of the northern basin dry, losing a third of its current surface area. Scientific models predict water levels could fall up to 21 meters by 2100.

Lake Constance in Europe has also been affected by high temperatures, with rising evaporation rates causing significant water level declines. Decades ago, it was suffering from severe nutrient pollution, which led to ecological collapse and algae blooms. However, improvements in wastewater treatment and phosphorus removal have stabilized fish populations and allowed the lake to recover.

The Aral Sea, once the fourth-largest lake in the world, suffered a devastating decline due to water extraction for irrigation. By 2010, its surface area had shrunk by over 50,000 square kilometers, creating the Aralkum Desert and displacing communities. The North Aral Sea has benefited from the Kok-Aral Dam, which has helped raise water levels, while areas where restoration is unlikely have seen the planting of saxaul shrubs to stabilize the sand and prevent dust and toxic residues from spreading.

In the United States, Muskegon Lake was heavily polluted with industrial waste and contaminated sediment. Extensive clean-up efforts removed contaminated soil and waste, restoring 54 hectares of shoreline and surrounding areas. While authorities have removed the lake from the list of severely degraded bodies of water, high contaminant levels in certain fish species still pose health risks.

Lake Chad, located in the Sahel, has undergone considerable fluctuations in size due to climate change, irrigation, and deforestation. Covering up to 25,000 square kilometers in the 1960s, it has lost over 90% of its area during severe droughts. The lake now supports the livelihoods of 30 million people, and its decline has contributed to a wider ecological crisis in the region.