Climate change is causing lakes to turn less blue, with many at risk of turning green-brown permanently, according to a new study.
Led by the American Geophysical Union, the study presents the first “global inventory of lake color” and takes into account changes in water color to determine water quality.
Although no specific time frame has been offered, the researchers said that one in 10 lakes can be expected to change color in “the future”.
Blue lakes are generally found in the coldest regions of the Earth and are not very common, representing only 31% of the world’s lakes. Compared to lakes with greener or browner water, they are generally deeper and more susceptible to ice cover during the winter.
The study, published Thursday in the journal Geophysical Research Letters, found that rising temperatures, leading to less ice, are the main culprit behind the color change of blue lakes.
“No one has ever studied the color of lakes on a global scale,” Xiao Yang, co-author of the study, said in a statement.
“There have been previous studies of maybe 200 lakes around the world, but the scale we’re trying here is much, much larger in terms of the number of lakes and also the coverage of small lakes. Although we don’t study every lake on Earth, we try to cover a large and representative sample of the lakes we have.
Covering the hues of 85,360 lakes and reservoirs around the world from 2013 to 2020, the study’s researchers used 5.14 million satellite images.
Typically, a lake’s change in color is attributed to algae and other sediments, but new research now suggests that varying degrees of warming could also impact water color due to climate change.
The lakes likely to be affected are in northeastern Canada, New Zealand, the Rocky Mountains and northern Europe, according to the study.
The lakes’ color change has already begun, according to study co-author Catherine O’Reilly, who pointed to the North American Great Lakes that have “increased algal blooms” and are also “among the lakes which heat up the fastest.
Yang also said a similar trend can be seen in arctic regions that are beginning to have lakes with “increasing greenness.”
Changes in the color of the lakes could have devastating effects on those who depend on the lakes for drinking water, sustenance or fishing.
“There may be times when the water is not usable and the fish species may no longer be present, so we will not get the same ecosystem services essentially from these lakes when they turn from blue to green” , O’Reilly said.
It could also mean that the lakes will no longer be used for recreational purposes.
“Nobody wants to go swimming in a green lake,” O’Reilly said.
“So aesthetically some of the lakes that we would have always considered refuge or spiritual places, those places might be disappearing.”