Conducted 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 was offered, researchers said one in 10 lakes can expect to change color in the “future.” Blue lakes are generally found in the colder regions of Earth and are not very common, accounting for just 31 percent of the world’s lakes. Compared to lakes with greener or browner water, they are usually deeper and more likely to be covered by ice during the winter. The study, published Thursday in the journal Geophysical Research Letters, found that rising temperatures, leading to shrinking ice, are the main culprit behind the changing color of the 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 release. “There were earlier studies of maybe 200 lakes around the world, but the scale we’re attempting 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 worldwide from 2013 to 2020, the study’s researchers used 5.14 million satellite images. Generally, a lake’s color change is attributed to algae and other sediments, but new research now shows that varying degrees of warming could also be affecting the water’s color due to climate change. The lakes most likely to be affected are in northeastern Canada, New Zealand, the Rockies and northern Europe, the study says. Lake discoloration has already begun, according to study co-author Catherine O’Reilly, who pointed to North America’s Great Lakes that have “increased algal blooms” and are also “among the warming lakes faster”. Yang also said a similar trend can be seen in Arctic regions that are starting to have lakes with “intensifying greening.” Changes in lake colors could mean devastating effects to those who rely on lakes for drinking water, food or fishing. “There may be periods where the water is unusable and the fish species may no longer exist, so we’re not going to get the same ecosystem services essentially from those lakes when they shift from blue to green,” he said. O’Reilly. It could also mean that the lakes will no longer be used for recreational purposes. “No one wants to go swimming in a green lake,” O’Reilly said. “So, aesthetically, some of the lakes that we may have always thought of as sanctuary or spiritual places, those places may be disappearing.”
