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National Center for Ecological Analysis and Synthesis

A lake with trees reflecting in the water

The global carbon cycle is the process by which carbon in its many forms moves through soil, water, and other parts of the biosphere, and it profoundly affects all life on Earth. For example, the cycle includes the absorption and release of carbon dioxide, making it key to the science of climate change.

One NCEAS working group helped to fill an important knowledge gap in the scientific understanding of the carbon cycle – the role of inland freshwater ecosystems, such as lakes, rivers, and reservoirs – thus contributing to a more complete view for understanding how carbon shapes our world.

Scientists knew inland waters are important in three carbon processes: they transport carbon to the ocean, bury it in sediments, and exchange it with the atmosphere. But since they account for only about 0.05% of all the water on the planet, scientists had rarely considered them as important components of the carbon cycle.

That changed when the working group published the first calculation of the amount of carbon in inland waters. They found that roughly two petagrams (Pg) of carbon – that’s two billion metric tons – enter them from land annually, which more than doubled scientists’ previous estimation of the total amount of carbon lost by land. For comparison, the burning of fossil fuels releases about six petagrams of carbon into the atmosphere per year.

This means, when it comes to understanding the global carbon cycle, accounting for inland waters really matters.

“Although their area is small, these freshwater systems can affect both regional carbon balances and the global balance as well. Their inclusion provides useful insight about the storage, oxidation, and transport of terrestrial carbon, and may warrant a revision of how the modern net carbon sink on land is described,” says Jonathan Cole, emeritus faculty at the Cary Institute of Ecosystem Studies and the working group’s principal investigator.

The group’s findings also demonstrate the power of synthesis in advancing scientific knowledge. By facilitating the distillation of large amounts of environmental information, NCEAS helped these scientists get a more complete picture of an important Earth system. 

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