Somebreathtaking blue lakes may not be so blue in the future, thanks to climate -组卷网

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Some breathtaking blue lakes may not be so blue in the future, thanks to climate change. In the first global record of lake color, researchers estimate that roughly one-third of Earth’s lakes are blue. But, if average summer air temperatures should rise by a few degrees, some of those pure waters could turn green or brown, the team reports in the Geophysical Research Letters.

Lake color depends in part on what’s in the water, but factors such as water depth and surrounding land use also matter. Compared with blue lakes, green or brown lakes are caused by more algae (水藻), sediment and organic matter, says Xiao Yang, a hydrologist at Southern Methodist University. If some lakes do become less blue, people will probably lose some of the resources they have valued.

Yang and his colleagues used satellite photos from 2013 to 2020 to analyze the color of more than 85, 000 lakes that are detectable around the world. The scientists found that lakes in cooler regions, with average summer temperatures below 19℃, tend to have a blue color compared to lakes with warmer water. This warmer environment encourages more algae growth, and thus its tint is changed, giving it a green-brown look, according to Yang. But what is worth mentioning is that the average summer temperatures may increase another 3℃—an amount that scientists think is possible by the end of the century.

Lake color can suggest the stability of a lake’s ecosystem, with shifting shades indicating changing conditions for the creatures living in the water. One benefit of the new study is that it gives scientists a baseline for assessing how climate change is affecting Earth’s freshwater resources. Continued monitoring of lakes could help scientists detect future changes.

【小题1】What contributes to blue lakes?