An increase in the number of small lakes on Earth is bad news for the climate

The Sciences I noticed an increase in the number of lakes on the planet over the past 40 years. And while it may not seem like it, this is worrying, as the development results in an increase in greenhouse gases being released from the world’s water reservoirs.

Between 1984 and 2019, the land area covered by lakes grew by more than 46,000 square kilometers worldwide, which is slightly larger than that of Denmark, for comparison purposes. These bodies of water constantly produce carbon dioxide, nitrous oxide, methane, and many other gases, which are by-products of feeding fungi and bacteria from the bottom, which eat dead plants and animals from the place.

Consequences of rising lakes

In terms of carbon emissions, the annual increase proportional to the increase in lakes represents 4.8 teragrams (trillion grams), or roughly 5 million tonnes of carbon dioxide, equal to all UK emissions in 2012, for example. The changes, according to scientists, are greater and faster than usual.

In addition to greenhouse gases, the ecosystem and access to water resources also suffer from these changes. New knowledge about the extent and dynamics of the world’s lakes has allowed us to better calculate their potential to emit carbon dioxide.

For the research that collects this data, satellite imaging technologies and deep learning algorithms were used, covering 3.4 million lakes around the world. Small lakes (less than 1 square kilometer), incl., are particularly important for calculating GHGs, because they generate a large volume of emissions relative to their size.

The effect of small lakes

Smaller lakes make up only 15% of the global coverage of these bodies of water, but they are responsible for about 45% of the increase in carbon dioxide emissions and 59% of the increase in methane emissions in the period studied by the scientists.

According to experts, the emissions are disproportionate because small lakes usually end up accumulating more organic matter, which eventually turns into gases. They are also usually shallow, making it easier for material to rise to the surface and then into the atmosphere.

In addition, the bodies of water Smaller ones are more sensitive to changes in climate and weather, as well as human interventions. Thus, their size and water chemistry have significant differences, which requires more urgent identification and mapping, as they are also more expensive.

More than half of the increase in lake coverage has been due to human intervention, mainly through reservoir construction; The rest ends up going down in account of melting glaciers and permafrost from global warming.

The data is expected to be useful for future climate models, as a significant amount of potential greenhouse gases could come from lake surfaces as ice melt continues to increase around the world. Using the data, it will also be possible to better estimate aquatic freshwater resources and assess flood risks, as well as better manage sites, as this also affects biodiversity.

source: Nature Communications🇧🇷 Copenhagen University

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