A new study published on Monday 9 November 2015 in the acclaimed journal Nature Geoscience shows that lakes in the northern latitudes will release substantially more CO₂ in the future because of global warming.

The study, based on extensive data from more than 5,000 Swedish lakes, is led by Professor Gesa Weyhenmeyer, Department of Ecology and Genetics/Limnology, Uppsala University.

Professor Erik Jeppesen, Department of Bioscience and Arctic Research Centre, Aarhus University, is co-author and has participated in the extensive data work. He says:

“Everything indicates that the release of carbon dioxide from the lakes in northern to southern Sweden increases as it gets warmer and because the areas adjacent to the lakes are increasingly used for, for example, agriculture instead of being planted with forest.”

Thus, today, a small southern Swedish lake releases twice as much CO₂ as a similar northern Swedish lake.

“It worries us. There is great risk that the carbon dioxide release from lakes will increase significantly in the northern parts of Scandinavia, Russia and Canada as the climate warms. And this is where the vast majority of the world’s lakes are found,” says Erik Jeppesen.

As we burn more fossil fuels, the amount of greenhouse gases in the atmosphere increases and so do temperatures. And the new study therefore shows that warming has a cumulative effect that increases the CO₂ release from freshwater wetlands to the atmosphere, contributing to global warming.

The study further demonstrates that the CO₂ released from the Swedish lakes comes particularly from the catchment where it is formed by the biological turnover in the soil. From there, the CO₂ runs off into rivers and then into the lakes where it is later released into the atmosphere. This recognition is in contrast to most previous world-wide studies concluding that the majority of the released CO₂ comes from the turnover in the lake itself.

“When we assess the future release of carbon dioxide to the atmosphere, it is important to know where the carbon dioxide comes from. Only with this knowledge can we find ways to reduce the release,” says Gesa Weyhenmeyer.

"Significant fraction of CO₂ emissions from boreal lakes derived from hydrologic inorganic carbon inputs" by Gesa A Weyhenmeyer, Sarian Kosten, Marcus B Wallin, Lars J Tranvik, Erik Jeppesen and Fabio Roland. Nature Geoscience 2015, doi:10.1038/ngeo2582