Earth’s large lakes are shrinking
Lakes play a crucial role in providing freshwater and support many essential ecosystem services. In a new study, we found significant water losses in 53% of large lakes on Earth in the past 28 years. These losses are attributed to human consumption, warming climate, and sedimentation. Two billion people reside in areas where lakes are drying, underscoring the urgent need for management solutions.
To understand the reasons behind water losses or gains in lakes, we identified three key factors. First, we analyzed ‘natural’ changes by examining precipitation and river flow, which are primarily influenced by natural climate variability. Secondly, we investigated the impacts of climate change by studying temperature and evaporative demand, i.e., measuring how ‘thirsty’ the atmosphere is. Lastly, we considered human water consumption by incorporating data from models. Using statistical techniques, we modeled the response of lake volume variability to changes in these climate and human variables.
Our findings indicate that 53% of Earth’s large water bodies experienced drying between 1992 and 2020. What is surprising is that this phenomenon occurred not only in arid regions but also in humid regions. Previous climate studies indicate a “dry-get-drier and wet-get-wetter” pattern in a warming climate. This is widely recognized in observations and models. Our study confirms a “dry-get-drier” pattern in lake water storage. However, we also observed widespread lake water losses in the humid tropics and high latitude regions over the last three decades, suggesting that drying lakes worldwide are more extensive than previously thought, certainly concerning lake water storage.
More than half of the total water loss in natural lakes can be attributed to both warming and increased human water consumption. Therefore, the widespread global declines in lake water storage may signify global aridification under warming and increasing human water use. Additionally, our study reveals that sedimentation dominated the total water loss in existing reservoirs filled before 1992. Sedimentation is an ongoing, slow process that gradually reduces the capacity of reservoirs to store water, thereby becoming less reliable for freshwater and hydroelectric energy supply. Reservoir sedimentation rates can accelerate under climate change due to increasing extreme precipitation, as well as land disturbances such as wildfires, landslides, and deforestation.
By providing new insights into the extent of changes occurring in global lakes, our study aims to raise awareness about this issue. It is important to note that approximately a quarter of the global population lives in a basin with a large, drying lake. The potential impacts of drying lakes, such as freshwater shortages, environmental degradation, and hydropower energy reduction, can be significant. Therefore, it is crucial to manage lakes effectively to maintain healthy levels in order to mitigate the impacts, ensuring long-term sustainability.
Original Article:F. Yao, B. Livneh, B. Rajagopalan, J. Wang, J. Cretaux, Y. Wada, M. Berge-Nguyen. 2023. Satellites reveal widespread decline in global lake water storage. Science, 380(6646), 743-749, doi: 10.1126/science.abo2812.
Alba Covelo Paz , Junior Scientific Editor
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