If global warming continues, Blue lakes around the world risk turning into a greenish-brown hue., according to a new study that includes the first world inventory of the color of lakes. According to their authors, changes in the tonality of the lakes can indicate: loss of ecosystem health.
While substances such as algae and sediment can affect the color of lakes, the new study concludes that air temperature, precipitation, and lake depth and height are also factors that play a role in lakes’ color.
Blue lakes, which make up less than a third of the world’s lakes, tend to be deeper and are found in cold, high latitudes, areas with high rainfall and winter ice cover. Greenish-brown lakes, which make up 69% of all existing lakes, are more common and are found in drier regions, inland and along shorelines.
Research published Geophysical Research Lettersjournal of scientific entity AGU.
Researchers used 5.14 million satellite images of 85,360 lakes and reservoirs worldwide between 2013 and 2020 to determine the most common color of water in these ecosystems.
“No one has studied the color of lakes on a global scale”said Xiao Yang, a remote sensing hydrologist at Southern Methodist University and author of the study. “There have been previous studies of maybe 200 lakes around the world, but the scale we’re looking at here is much larger in quantity, including small lakes. While we haven’t studied all the lakes in the world, we tried to analyze a large, representative sample of the planet.”
A lake’s color can change seasonally, in part due to changes in algae growth, so the authors determined the color by evaluating the most common hue over seven years.
Global warming is changing lakes
However, climate change causes a global change in this regard. Global warming of the planet could reduce the percentage of blue lakes, many are found in the Rocky Mountains, northeastern Canada, northern Europe, and New Zealand.
“The warmer water that causes more algae growth will tend to turn the lakes green.” Explained Catherine O’Reilly, a water ecologist at Illinois State University (USA) and author of the study. “There are many examples of people actually seeing this by looking at a single lake,” she said.
For example, The North American Great Lakes are experiencing increased algal blooms and are also among the fastest warming lakes on the planet.said O’Reilly. Yang said previous research has also shown that remote Arctic regions have lakes that are “increasingly greener.”
While the authors have used more complex and detailed systems to understand the overall health of these ecosystems in previous studies, water color is also a strong indicator of water quality and can also be seen from satellites.
“If you’re using a lake for fishing or obtaining water, changes in the quality of that water when that lake turns green will increase the difficulty of obtaining these resources,” O’Reilly said.There may be periods when the water is unavailable and fish species are no longer available.that is, when it changes from blue to green, we will not be able to receive the same ecosystem services from those lakes.”
As warming continues, northern European lakes are likely to lose their winter ice cover, which could also affect social, economic and cultural activities.
“No one wants to go swimming in a green lake.” “Aesthetically, some lakes that we always think of as sanctuaries or spiritual places may be disappearing as the color changes,” O’Reilly said.
Reference work: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL098925