Climate change may turn some blue lakes green or brown.

 Climate change may turn some blue lakes green or brown

In the first global census of lake colors, scientists analyzed more than “85,000 lakes” around the world and concluded that nearly a third of the Earth’s lakes are blue, but when average summer air temperatures rise by a few degrees, we find that some of this clear water may It turns dark green or brown, according to the research team fromSouthern Methodist University. Changing lake colors can play a role in changing how people use that water, and can provide clues about the stability of lake ecosystems. The color of the lake depends on what is in the water, but there are other important factors such as the depth of the water and the uses of the land surrounding it. Compared with blue lakes, green or brown lakes contain more algae, sediments and organic materials, says Xiao Yang, a scientist. Hydrology at Southern Methodist University in Dallas, United States.

Satellite images to track the colors of lakes

Yang and his colleagues used satellite images from 2013 to 2020 to analyze “85,000 lakes” around the world or more. Since storms and changing seasons can temporarily affect the color of a lake, the researchers focused on the most common color observed from each lake. lake during the seven-year period referred to, and the researchers also created an interactive map online that can be used to explore the colors of these lakes. “The approach followed in this study is “A very exciting approach, as satellite data represents strong information and evidence that can be built upon in the future.” The research team looked at local climates during that period to see how they might be linked to the color of lakes around the world. For many small or remote bodies of water, there are no records of temperature and precipitation; So the researchers relied on climate forecasts calculated for every spot on the Earth, which were compiled together from relatively disparate sources. The researchers found that lakes in places where average summer air temperatures are below 19 degrees Celsius are more likely to turn blue, as up to 14 percent of the blue lakes they studied were found at this temperature limit. But when average summer temperatures increase by another 3 degrees Celsius, an amount scientists believe is reasonable, by the end of the century, “3,800 lakes” could turn green or brown. This is because warm water helps algae multiply more; Which changes the properties of the water, giving it a brown or green color, says Yang.

Changes in the colors of lakes and what they mean

The research team faced some difficulties in monitoring a large number of lakes, says study co-author Catherine O’Reilly, an aquatic ecologist at Illinois State University, who added: “We do not know how many lakes there are in the world. Many of the lakes are so small that “They cannot be reliably detected by satellite, but according to some estimates, tens of thousands of large lakes may lose their beautiful blue color.” The danger of the colors of lakes turning green or brown is that some of the resources acquired by surrounding communities will lose their value if some lakes become less blue, as lakes are often used for drinking water or providing food through the fish that are caught. Or even for recreational purposes, but if the water is clogged with algae, it may require more expensive cleaning for drinking, and it may also greatly affect the species that live in these lakes.

Color changes do not necessarily mean that lakes are less healthy at all. The matter requires studying the diversity in each lake, and the conditions in which it exists. An increase in algae may represent good news for specific types of fish, contrary to the prevailing belief in the absolute evil of algae growth. The color of the lake can indicate the stability of the lake's ecosystem, as the changing colors of lakes indicate the changing conditions of the creatures that live in the water. One advantage of the new study is that it provides scientists with a basis for evaluating howclimate change will affect the Earth's freshwater resources, and continued monitoring of the lakes could help scientists detect future changes. In conclusion, Mike Pace, an aquatic ecologist at the University of Virginia, who was not involved in the study, says: “The study sets a baseline against which we can compare future results, and this, to me, is the great benefit of this study.”