Emergence of new small lakes contributes to rise in greenhouse gas emissions

Emergence of new small lakes contributes to rise in greenhouse gas emissions

Just under half of the total lakes globally are in the top of the northern hemisphere, including the likes of Scandinavia, Alaska, Russia, and Greenland. File photo: Anthony Devlin/PA Wire

A proliferation of new small lakes has emerged across the planet in recent decades, bringing a new source of unwanted greenhouse gas emissions, new research has found.

Scientists from a number of universities undertook a global survey of 3.4 million lakes, finding that the number of new lakes has "increased substantially" in almost 40 years, with a surface expansion equal to the size of Denmark, or 46,000 sq km.

Smaller lakes have been particularly conspicuous, the study published in Nature Communications found. Climate change and human behaviour are the main reasons behind the new lakes, it showed.

University of Copenhagen assistant professor of biology and co-author of the study, Jing Tang, said the new smaller lakes have a significant effect on emissions.

She said:

Small lakes emit a disproportionate amount of greenhouse gases because they typically accumulate more organic matter, which is converted into gases. And also, because they are often shallow. 

"This makes it easier for gases to reach the surface and up into the atmosphere."

The likes of bacteria and fungi feeding on dead plants and animals at the bottom of a lake emit vast amounts of CO2, methane, nitrous oxide, and other gases, the researchers said.

The study found that while small lakes make up 15% of total lake area, they account for 25% of carbon and 37% of methane emissions. Furthermore, they also contribute to 45% and 59% of the net increases of the lake carbon and methane emissions respectively since 1984, the data show.

Reservoirs or artificial lakes account for more than half of increased lake area, while the other half are usually created by melting glaciers or thawing permafrost, the survey showed.

Just under half of the total lakes globally are in the top of the northern hemisphere, including the likes of Scandinavia, Alaska, Russia, and Greenland.

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