Quantity of Lakes on Earth Has Grown Significantly in Recent Decades

According to a unique global survey of 3.4 million lakes in which the University of Copenhagen participated, the number of lakes on our planet has increased significantly in recent decades.

There has been an increase in the number of small lakes, which unfortunately emit a lot of greenhouse gas.

The development is critical for the Earth's carbon balance, global ecosystems, and human access to water resources.

Earth's many new lakes

(Photo : Aaron Burden/Unsplash)

Bacteria and fungi at the lake's bottom that feed on dead plants and animals emit massive amounts of CO2, methane, nitrous oxide, and other gases.

Some of these gases make their way into the atmosphere, as per ScienceDaily.

Lakes act as greenhouse gas factories as a result of this mechanism. In fact, freshwater lakes are responsible for approximately 20% of all global CO2 fossil fuel emissions into the Earth's atmosphere.

According to projections, climate change will cause lakes to emit an increasing proportion of greenhouse gases in the future.

This is just one of the reasons why it is critical to understand the number and size of these lakes, as well as how they develop.

This information was previously unknown. Scientists from the University of Copenhagen and other universities have created the most accurate and detailed map of the world's lakes ever created.

Using high-resolution satellite imagery combined with artificial intelligence, the researchers mapped 3.4 million lakes and their evolution over the last four decades.

According to the survey, the area of global lake surfaces increased by over 46,000 km between 1984 and 2019 - slightly more than Denmark's surface area.

Lakes have undergone significant and rapid changes in recent decades, affecting greenhouse gas accounts, ecosystems, and access to water resources.

Their newfound understanding of the extent and dynamics of lakes, for example, allows us to better calculate their potential carbon emissions, explained Jing Tang, an Assistant Professor in the Department of Biology and co-author of the study, which was published in Nature Communications.

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Large CO2 emissions from small lakes

Since 1984, an increasing number of small lakes have appeared.

According to the researchers, the number of these small lakes is especially important because they emit the most greenhouse gases in relation to their size.

Despite accounting for only 15% of the total lake area, small lakes account for 25% of CO2 and 37% of methane emissions.

Furthermore, they account for 45% and 59% of the net increases in lake CO2 and CH4 emissions from 1984 to 2019.

Small lakes emit a disproportionate amount of greenhouse gases because they accumulate more organic matter, which is converted into gases, and because they are frequently shallow.

New figures have been sent to the United Nations

The new dataset, according to the researchers, has a variety of regional and global applications, as per the University of Copenhagen.

"I have sent our new greenhouse gas emission estimates to those in charge of calculating the global carbon budget, those behind the UN's IPCC climate reports, and I hope they will include them in updating the global emission numbers," Jing Tang said.

She continued, "The dataset can also be used to make better estimates of freshwater lake water resources and to better assess the risk of flooding, as well as for better lake management, because lake area affects biodiversity as well."

Researchers mapped 3.4 million lakes (with the smallest lake size of 0.03 km2) and how their sizes changed between 1984 and 1999, 2000 and 2009, and 2010 and 2019.

This study's GLAKES dataset was created using high-resolution satellite imagery and a deep learning algorithm.

The dataset is freely accessible to the public.

The findings of the study were published in the scientific journal Nature Communications.

The study's first authors are Xuehui Pi and Qiuqi Luo from Southern University of Science and Technology in Shenzhen, China, and The University of Hong Kong in Hong Kong Special Administrative Region, China.

Yang Xu, Rasmus Fensholt, and Martin Brandt from the Department of Geosciences and Natural Resource Management at the University of Copenhagen also contributed to the study.

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