Human activities have caused more than half of the world’s largest lakes to shrink dramatically over the past 30 years, according to a new study published in the journal Science. The consequences pose risks to human health, economies and the natural world.
Combined, researchers found, the global decline in water storage is equivalent to 17 Lake Meads — the largest reservoir in the United States
Humans overusing water for agriculture and development and anthropogenic climate change are the primary causes of the decline, especially in natural lakes, said Fangfang Yao, the study’s lead author. In reservoirs, dirt and sand accumulated behind dams also played a large role in falling water levels.
The results were staggering, the authors said.
“About a quarter of the world’s population lives in a basin with a drying lake,” Yao said. “So the potential impact could be significant.”
The study examined nearly 2,000 of the planet’s largest lakes and reservoirs, using three decades of satellite observations and climate models to measure how bodies of water have shrunk or grown over time, and to analyze what influenced the change. For example, did a lake shrink due to increased evaporation with warmer temperatures or because it was diverted for agriculture?
The results revealed “significant declines,” the research paper said, across 53% of the lakes and reservoirs studied by the team from the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences.
At least half of the decline in natural lakes was driven by anthropogenic climate change and overuse. It’s a finding, Yao said, that should help water managers better manage and protect endangered lakes around the world.
“If you know that a lake is declining and the loss is attributable to human activities, then we can put more emphasis on conservation and improving water efficiency,” Yao asked.
A climate change-driven mega-drought and an ever-growing human thirst have continued to drain the two largest reservoirs in the United States—Lake Powell and Lake Mead, which the Colorado River feeds. Lake Chad, one of Africa’s largest freshwater lakes, which supplies nearly 40 million people with water, has shrunk by an estimated 90% since the 1960s.
The UN considers access to clean drinking water a universal human right. But its own figures show that about 2 billion people around the world do not have access to it, and about half the world’s population experiences severe water scarcity at least once a year.
“Uncertainties are increasing,” said Richard Connor, editor-in-chief of a UN water report published earlier this year at a press conference in late March where world leaders met to try to find better strategies to manage the planet’s scarce fresh water. “If we don’t solve it, there will definitely be a global crisis.”