According to a recent study that provides the first global inventory of lake color, blue lakes all over the world run the risk of turning green-brown if global warming continues. Changes in lake water color may be a sign of an unhealthy lake ecosystem.
The new study finds that, in addition to factors like algae and sediments, air temperature, precipitation, lake depth, and elevation also have a significant impact on the most common water color of lakes.
Less than one-third of the world’s lakes are blue, and they are typically deeper and found in cool, high-latitude areas with lots of precipitation and winter ice cover. According to the study, green-brown lakes, which make up 69% of all lakes, are more common and can be found in drier areas, in the interiors of continents, and near coastlines.
The new study was released in Geophysical Research Letters, a journal of the American Geophysical Union that publishes high-impact, brief reports with immediate implications in all Earth and space sciences.
To identify the most prevalent water color of 85,360 lakes and reservoirs worldwide from 2013 to 2020, the researchers used 5.14 million satellite images.
Nobody has ever investigated the hue of lakes on a global scale, according to study author and remote sensing hydrologist Xiao Yang of Southern Methodist University. “The scale we’re attempting here is much, much larger in terms of the number of lakes and also the coverage of small lakes, compared to previous studies that involved perhaps 200 lakes around the world. Despite the fact that we are not researching every lake on the planet, we are attempting to cover a sizable and representative sample of the lakes that exist.”
The authors evaluated the most frequent lake color over a period of seven years to characterize lake color because a lake’s color can change seasonally in part due to changes in algal growth. The authors created an interactive map that allows users to explore the findings.
The new study also looked at how different levels of warming might impact water color if climate change continues. According to the study, the number of blue lakes, which are abundant in the Rocky Mountains, northeastern Canada, northern Europe, and New Zealand, may decrease due to climate change.
According to Catherine O’Reilly, an aquatic ecologist at Illinois State University and the study’s lead author, warmer water, which causes more algal blooms, tends to turn lakes greener. There are numerous instances where this has actually been observed, according to research into a single lake.
For instance, O’Reilly cited the North American Great Lakes as one of the lakes that are warming up the fastest and experiencing increased algal blooms. According to previous studies, isolated Arctic regions have lakes that are “intensifying green,” said Yang.
Water color is a straightforward yet useful metric for water quality that can be seen from satellites at the global scale, according to the authors, whereas earlier studies have used more complicated and finer scale metrics to understand overall lake ecosystem health. This methodology offers a way to investigate how climatic changes are affecting remote lakes.
“If you use lakes for fisheries, food, or drinking water, changes in water quality that are likely happening when lakes become greener will probably mean it will cost more to treat that water,” said O’Reilly. We won’t essentially receive the same lake ecosystem services from those lakes when they turn from blue to green because there might be times when the water isn’t usable and certain fish species aren’t present.
In countries like Sweden and Finland, where lakes are prevalent culturally, changes to water color may also have recreational and cultural effects, according to O’Reilly. Lakes in northern Europe will probably lose their winter ice cover as global warming progresses, which could have an impact on winter and cultural activities.
Aesthetically, some of the lakes that we may have always thought of as a refuge or as spiritual places, those places might be disappearing as the color changes. “Nobody wants to go swimming in a green lake,” said O’Reilly.
