The Impact of Climate Change Turns 85,000 Blue Lakes Green

The impact of climate change has become the subject of much research by scientists, one of which is changes in the color of lakes. Scientists analyzed more than 85,000 lakes around the world, or approximately a third of the world's lakes are blue, due to the impact of climate change. Some beautiful blue lakes may not be blue anymore in the future, thanks to climate change.

If the average summer air temperature rises a few degrees, some of the crystalline water could turn cloudy green or brown, as the research team reported in Geophysical Research Letters on December 28, 2022. Compared with blue lakes, green or brown lakes have more algae, sediment, and organic matter, said Xiao Yang, a hydrologist at Southern Methodist University in Dallas.

Xiao Yang and colleagues used satellite photos from 2013 to 2022 to analyze the color of more than 85,000 lakes around the world. The researchers focused on the most frequently observed colours for each lake over a nine-year period.

The scientists then looked at local climate changes over that time to see how they might be linked to the color of lakes around the world. The researchers created calculated climate records for each place in the world studied.

Lakes in places with average summer air temperatures below 19° Celsius are more likely to be blue than lakes with warmer summers, the researchers found.

But up to 14 per cent of the blue lakes they studied were near that threshold. If average summer temperatures rise another 3 degrees Celsius - an amount scientists say is reasonable by the end of the century - those 3,800 lakes could turn green or brown. That's because warmer water helps algae grow more, which changes the properties of the water and gives it a green-brown color.

Extrapolation beyond this sample of lakes is somewhat tricky. Many lakes are too small to be detected via satellite, but according to some estimates, tens of thousands of larger lakes could lose their blue hue.

If some lakes become less blue, people may lose some of the resources they value. Lakes are often used for drinking water, food or recreation. If the water is clogged with algae, it certainly won't be interesting to visit or even drink the water.

But a change in color doesn't mean that the lake is any less healthy. The color of a lake can signal the stability of a lake's ecosystem, with changes in color indicating changes in the conditions of living creatures in the water.

This new study provides a basic understanding of how climate change affects Earth's freshwater resources and detects future changes.