A new study led by Professors ZHANG Yunlin and SHI Kun from the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (NIGLAS), has completed the first global assessment of lake water clarity, revealing widespread changes driven by climate and human activities. 

Published in Science Bulletin, the research analyzed 1.4 million satellite images to track the transparency of 170,799 large lakes from 1995 to 2023.

Results reveal that about 67% of global lakes have experienced a decline in transparency, with 39% showing significant decreases. On average, global lake transparency declined by about 13% over the study period, indicating the widespread impact of climate warming on lake ecosystems. 

In North America and Europe, rising temperatures, permafrost thawing, and algal proliferation were identified as major contributors to declining clarity. 

In contrast, about 44% of lakes in Asia exhibited increasing transparency. This improvement is linked to watershed “greening”—vegetation recovery that acts as a natural filter, reducing sediment and nutrient runoff.

“Our work is the first to unravel how climate, watershed dynamics, and in-lake processes collectively shape the lake light environment on a global scale,” said Professor ZHANG. The findings offer new insights for ecosystem protection and sustainable lake management in the face of global environmental change.