When lakes decline, can they recover?

Some of the world's largest lakes may shrink substantially within this century, impacting ecosystems and around a quarter of the global population living in affected areas. Although restoration efforts have worked in some cases, many inland bodies of water face extreme challenges.

The Caspian Sea, the largest inland body of water on Earth, is bordered by Iran, Russia, Azerbaijan, Turkmenistan, and Kazakhstan. Its surface area has rapidly receded since the 1990s due to dam construction and water management practices in the Volga River basin, as well as rising temperatures from burning fossil fuels. Scientific models predict water levels could fall up to 21 meters by 2100, leaving large parts of the shallow northern basin dry and eliminating nearly one-third of the lake's current surface area.

Lake Constance, shared by Germany, Austria, and Switzerland, has experienced high evaporation rates this summer, leading to significant water level declines. In the late 1970s, low water levels were not the main concern, as the lake suffered from severe nutrient pollution. Massive algal blooms and oxygen depletion in deeper waters threatened fish populations and led to swimming bans.

Stabilizing the lake through wastewater treatment and phosphorus removal helped the ecosystem recover, benefiting around 4 million people in Baden-Württemberg who rely on it for drinking water.

The Aral Sea, once the fourth-largest lake on Earth, saw its surface area shrink by more than 50,000 square kilometers due to water extraction for irrigation during the Soviet era. Thirty fish species that supported commercial operations have disappeared, and entire communities along the former shoreline have vanished. The North Aral Sea has benefited from the Kok-Aral Dam, raising water levels, while efforts to plant saxaul shrubs aim to stabilize the sand and reduce contaminated dust.

In Michigan, Muskegon Lake was polluted by industrial waste and contaminated sediment. Extensive clean-up efforts removed contaminated soil and historic sawmill waste, restoring 54 hectares of shoreline and surrounding areas. Authorities removed Muskegon from the list of severely degraded lakes, generating $28 million in additional recreational value annually and attracting 500,000 extra visitors each year.

However, contaminant levels in certain fish species remain too high, and authorities continue to warn against eating them.

In Africa, Lake Chad, located in the Sahel, has partially recovered from severe droughts and continues to face pressure from climate change, irrigation, and deforestation. Its size now fluctuates between roughly 12,000 and 20,000 square kilometers. Climate change, irrigation, and deforestation continue to threaten the lake, impacting the food security of millions who depend on its resources.