Half of the world’s largest lakes and reservoirs are at risk of drying up, posing a grave concern for future freshwater availability and impacting ecosystems, human populations, and industries dependent on these water sources, a recently Science Magazine’s published study said.
More than half of the world’s largest lakes and reservoirs are dwindling and placing humanity’s future water security at risk, with climate change and unsustainable consumption the main culprits, a study said Thursday.
Unlike rivers, which have tended to hog scientific attention, lakes aren’t well monitored, despite their critical importance for water security, said Balaji Rajagopalan, a professor at the University of Colorado Boulder and co-author of the paper, which appeared in Science.
But high-profile environmental disasters in large water bodies like the Caspian and Aral Seas signalled to researchers a broader crisis.
To study the question systematically, the team, which included scientists from the United States, France, and Saudi Arabia, looked at Earth’s biggest 1,972 lakes and reservoirs, using observations from satellites from 1992-2020.
They focused on larger freshwater bodies because of the better accuracy of satellites at a larger scale and their importance for humans and wildlife.
Their dataset merged images from Landsat, the longest-running Earth observation program, with water surface height acquired by satellite altimeters, to determine how lake volume varied over nearly 30 years.
The results: 53 percent of lakes and reservoirs saw a decline in water storage, at approximately 22 gigatons a year.
For natural lakes, much of the net loss was attributed to climate warming as well as human water consumption.
Increased temperatures from climate change drive evaporation, but can also decrease precipitation in some places.
Lead author Fangfang Yao, a visiting fellow at CU Boulder, added in a statement: “Many of the human and climate change footprints on lake water losses were previously unknown, such as the desiccation of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina.”
One surprising aspect was that lakes in both wet and dry regions of the world are losing volume, suggesting the “dry gets drier, wet gets wetter” paradigm frequently used to summarize how climate change affects regions doesn’t always hold.
Losses were found in humid tropical lakes in the Amazon and Arctic lakes, demonstrating a trend more widely spread than predicted. Accumulating sedimentation was blamed for storage loss in drying reservoirs.
But although most global lakes were dwindling, nearly a quarter saw significant increases in their water storage.
These included the Tibetan Plateau, “where glacier retreat and permafrost thawing partially drove alpine lake expansion,” the paper said.
Globally, freshwater lakes and reservoirs store 87 percent of the planet’s liquid freshwater, underscoring the urgency of new strategies for sustainable consumption and climate mitigation.
Miroslava Salazar with AFP
