There are over 100 million lakes worldwide, but many are no longer what they once were. Climate change, pollution, and over-abstraction are transforming these freshwater ecosystems, sometimes causing lakes to shrink, flood, or turn green.
Dianna Kopansky, head of the Freshwater Ecosystems and Wetlands Unit at the United Nations Environment Programme (UNEP), warns: “Some of the world’s best-known lakes are a shadow of their former selves. They appeared much fuller and healthier a few decades ago. If we don’t act, it could be calamitous for hundreds of millions of people who depend on them.”
The first World Lake Day on 27 August highlighted the urgent need to safeguard these vital resources.
Climate Change Impacts
Rising temperatures and shifting rainfall patterns are destabilizing the global water cycle. In some regions, droughts are shrinking lakes, such as in Cape Town, South Africa. In others, increased rainfall is causing flooding, a growing concern for Kenya’s Lake Turkana.
Mountainous areas face additional risks from glacial-lake outbursts, which can trigger catastrophic downstream flooding as ice dams melt.
Human Over-Abstraction
Over-abstraction, or removing water faster than it can naturally replenish, is a major threat. Water is often diverted for cities, hydroelectric dams, or irrigation.
The Aral Sea in Central Asia is a prime example, having dramatically shrunk since the 1960s. In Bolivia, Lake Poopo has turned into a barren salt flat due to a combination of water diversions and climate change.
A 2024 UNEP and UN-Water report found that 364 basins worldwide, home to 93.1 million people, are experiencing significant lake losses.
Pollution Worsens the Crisis
Raw sewage, agricultural runoff, and industrial waste are adding pathogens, pesticides, and nutrients to lakes. Excess nitrogen and phosphorus can feed toxic algal blooms, deplete oxygen, and create dead zones hostile to aquatic life.
Lake Victoria in Africa is an example, where green waters indicate a surge in harmful bacteria. UNEP monitoring shows that more than one-quarter of 4,000 large lakes are becoming turbid, and nearly 15% show rising organic matter levels.
“These numbers should be a wake-up call,” says Kopansky. “We can’t continue to treat lakes like dumping grounds.”
Solutions for a Sustainable Future
Lakes supply 90% of the world’s surface freshwater and support an estimated 60 million livelihoods. Kopansky recommends three key actions:
- Implement integrated water resources management to balance human and ecological needs.
- Use basin-level approaches to involve local communities, Indigenous groups, and stakeholders in water and pollution management.
- Invest in data collection and monitoring to detect problems early.
“The technology and knowledge exist to reverse this trend,” Kopansky adds. “What we need now is the will to treat lakes as the precious resources they are.”