Researchers looked at 235 lakes around the world over the past 25 years and found that, on average, they are gaining a third of a degree (Celsius) every decade. The study, which used onsite measurements and satellite temperature data, found that warming was most pronounced in northern and tropical regions.
“These results suggest that large changes in our lakes are not only unavoidable, but are probably already happening,” lead author Catherine O’Reilly, associate professor of geology at Illinois State University, Normal, said in a statement.
CREDIT: Geophysical Research Letters
Disturbing the ecosystem of lakes could have huge impact on human life. The lakes in the study, which spanned the six inhabited continents, contain more than half the world’s fresh water. Earlier research has found that rising temperatures have decreased fish productivity in lakes.
“Lakes are important because society depends on surface water for the vast majority of human uses — not just for drinking water, but manufacturing, energy production, irrigation and crops,” paper co-author Stephanie Hampton of Washington State University said. “Protein from freshwater fish is especially important in the developing world.”
Algal blooms, for instance, have already emerged as a critical issue for freshwater, and the researchers expect them to get worse. During an algal bloom, microscopic algae particles proliferate and can release chemicals into the water that are toxic to humans and wildlife. A bloom in Lake Erie in 2014 led to a three-day bottled water advisory in Toledo. Most people across the world depend on lakes for fresh water supplies.
Algal blooms can also suffocate fish by absorbing oxygen in the water. The blooms have been tied to warmer water temperatures.
“At the current rate, algal blooms, which ultimately rob water of oxygen, should increase by 20 percent over the next century. Some 5 percent of the blooms will be toxic to fish and animals.”
Algal blooms are just one example of the impacts of climate change on freshwater sources. In tropical lakes, temperatures might have already reached nearly the upper limit for fish to live, the researchers suggested.
“Consequences of this extensive warming are numerous and diverse,” they write.
The warmer lakes are expected to contribute 4 percent more methane — a potent greenhouse gas — than otherwise projected, the study says. They may also see more evaporation, which, in turn, could hurt not only fish populations, but water security for the millions of people who depend on lakes around the world.