When lakes decline, can they recover?

The world's largest lakes may shrink significantly by the end of the century, posing severe threats to ecosystems and impacting roughly a quarter of the global population. While restoration efforts have been successful in some cases, many inland water bodies face daunting challenges. The Caspian Sea, the world's largest inland water body, has been rapidly shrinking since the 1990s due to dam construction and increased evaporation from climate change.

By 2100, water levels could drop up to 21 meters, potentially drying up large portions of the shallow northern basin. This decline has already led to increased dredging requirements, pressure on fish stocks and wetlands, and drying habitats for endangered species like the Caspian seal. Scientific warnings also suggest that exposed lakebeds could release dust and pollutants.

Lake Constance, shared by Germany, Austria, and Switzerland, experienced high evaporation rates this summer, causing water levels to drop significantly in some areas. Decades ago, the lake dealt with severe nutrient pollution, resulting in algal blooms, oxygen depletion, fish population threats, and swimming bans. However, wastewater treatment improvements and phosphorus removal from sewage have stabilized lake trout populations and stabilized the lake's ecosystem.

Nevertheless, the lake still faces challenges from shoreline development, invasive species, and climate change.

The Aral Sea, once the fourth-largest lake in the world, has shrunk by over 50,000 square kilometers since the Soviet era, causing a massive environmental catastrophe. Only a few fish species remain, and entire communities have disappeared. The North Aral Sea has benefited from a dam that has raised water levels, while saxaul shrubs are being planted to stabilize the sand and reduce contaminated dust. Over 1.8 million hectares have been planted since 2018, according to the Kazakh government.

In the United States, Muskegon Lake was once polluted by industrial waste and contaminated sediments. Extensive clean-up efforts removed contaminated soil and historic sawmill waste, restoring 54 hectares of shoreline and surrounding areas. As a result, authorities removed the lake from the list of severely degraded lakes in 2025.

The restoration efforts now generate an estimated $28 million in additional recreational value annually and attract roughly 500,000 extra visitors each year. However, certain fish species remain contaminated, and authorities warn against eating them.

In Africa, Lake Chad has been fluctuating in size due to climate change, irrigation, and deforestation. Covering up to 25,000 square kilometers in the 1960s, it has reduced to roughly 12,000 to 20,000 square kilometers today. The lake provides water for millions of people and wildlife, supporting livelihoods across the region. Climate change, irrigation, and deforestation continue to threaten its recovery, contributing to a broader ecological crisis affecting 30 million people who depend on the lake's resources.