A team of international researchers reported that some of the world's most important freshwater sources - from the Caspian Sea between Europe and Asia to South America's Lake Titicaca - lost water at a cumulative rate of around 22 gigatonnes per year for nearly three decades. That's about 17 times the volume of Lake Mead, the United States' largest reservoir.
Fangfang Yao, a surface hydrologist at the University of Virginia who led the study in the journal Science, said 56% of the decline in natural lakes was driven by climate warming and human consumption, with warming "the larger share of that".
Climate scientists generally think that the world's arid areas will become drier under climate change, and wet areas will get wetter, but the study found significant water loss even in humid regions. "This should not be overlooked," Yao said.
Scientists assessed almost 2,000 large lakes using satellite measurements combined with climate and hydrological models.
They found that unsustainable human use, changes in rainfall and run-off, sedimentation, and rising temperatures have driven lake levels down globally, with 53% of lakes showing a decline from 1992 to 2020.
Neary 2 billion people, who live in a drying lake basin, are directly affected and many regions have faced shortages in recent years.
Scientists and campaigners have long said it is necessary to prevent global warming beyond 1.5 degrees Celisus (2.7 degrees Fahrenheit) to avoid the most catastrophic consequences of climate change. The world is currently warming at a rate of around 1.1C (1.9F).
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