Some of the world's largest lakes are experiencing significant shrinkage, with implications for ecosystems and approximately a quarter of the global population residing in affected areas. Restoration efforts have shown success in certain instances, but many inland water bodies face considerable challenges.
The Caspian Sea, the largest inland water body on Earth, bordered by Iran, Russia, Azerbaijan, Turkmenistan, and Kazakhstan, has been rapidly receding since the 1990s. This decline is attributed to dam usage and water management practices in the Volga River basin, as well as increased evaporation rates due to rising temperatures linked to fossil fuel consumption. Scientific models predict that water levels could drop by up to 21 meters (68 feet) by 2100, with a 10-meter decline potentially drying out significant portions of the northern basin, reducing the lake's surface area by nearly one-third. The effects are already visible, with ports requiring extensive dredging, fish stocks and wetlands under pressure, and habitats for the endangered Caspian seal diminishing. Additionally, exposed lakebeds may release dust and pollutants, complicating conservation efforts among the five coastal states.
Lake Constance, bordered by Germany, Austria, and Switzerland, has also been affected by high temperatures, leading to significant evaporation. In the late 1970s, the lake faced severe nutrient pollution, risking ecological collapse due to algal blooms and oxygen depletion. Improvements in wastewater treatment and phosphorus removal have stabilized fish populations, benefiting local communities that rely on the lake for drinking water. However, challenges such as shoreline development, invasive species, and climate change persist, necessitating further restoration efforts.
The Aral Sea in Central Asia exemplifies the devastating impact of water extraction. Once the fourth-largest lake globally, it has shrunk by over 50,000 square kilometers since the Soviet era due to water diversion for agriculture. The disappearance of fish species and communities along the former shoreline has led to the emergence of the Aralkum Desert, which covers approximately 62,000 square kilometers. Dust storms from the lakebed pose health risks. However, the North Aral Sea has seen some recovery due to the Kok-Aral Dam, with efforts to stabilize the area through planting saxaul shrubs.
In Michigan, Muskegon Lake faced pollution from industrial waste, but extensive cleanup efforts have restored 54 hectares of habitat, leading to its removal from the list of severely degraded lakes in 2025. The restoration generates an estimated $28 million (€23 million) in additional recreational value annually, attracting around 500,000 extra visitors each year, although some fish species remain unsafe to eat due to high contaminant levels.
Lake Chad, located in the Sahel region, is a vital source of water for people and wildlife. It has fluctuated in size due to climate change, irrigation, and deforestation, with its area ranging from 12,000 to 20,000 square kilometers. The decline of Lake Chad has contributed to a broader ecological crisis, threatening food security for millions. Approximately 30 million people rely on the lake's resources, and investment projects worth $10 million have been initiated to preserve the lake as a habitat and economic resource for the region.