Inland waters release substantial amounts of greenhouse gases, but this is rarely included in climate assessments. New research from Umeå University shows that not accounting for carbon fluxes between land and water systems leads to incorrect assessments of climate impact and feedback on the carbon cycle.
Cold regions in the north and at high elevation are experiencing rapid warming – up to four times faster than the global average. This phenomenon not only threatens the status of these ecosystems but also leads to the release of vast amounts of greenhouse gases to the atmosphere. However, assessments of how the carbon cycle responds to and feeds back on climate change generally focus on the exchange of greenhouse gases on land, neglecting the large carbon export from land to the abundant inland waters (streams, rivers, and lakes) in these regions.
“Current data and approaches are likely inadequate to capture contemporary and future carbon flows across land and water systems,” says Jan Karlsson, Professor at the Department of Ecology and Environmental Sciences at Umeå University.
Emissions from 3,000 lakes
One example of a large-scale integrated assessment is new research led by Chunlin Song from Sichuan University in China and Jan Karlsson from Umeå University, published in the scientific journal Science Advances. Based on a comprehensive analysis of greenhouse gas emissions from over 3,000 lakes and rivers across the Northern Hemisphere, they show that lakes and rivers in cold regions contribute more to greenhouse gas emissions than previously understood and that these emissions could offset a major part of the carbon uptake by land ecosystems in the north.
The study also reveals regional differences in greenhouse gas emissions between rivers and lakes, with particularly high significance of rivers and of systems in regions with extensive coverage of permafrost.
“This finding is particularly alarming, as it suggests that thawing of permafrost releases significant amounts of stored carbon into the atmosphere, further exacerbating climate change.”
The implications of this research are profound, according to Jan Karlsson.
“As global temperatures continue to rise, the role of cold regions in greenhouse gas emissions may become increasingly significant,” he says.
Specific conditions
In another paper published in the scientific journal Nature Water, Jan Karlsson emphasizes that the climate impact on the coupled land-water carbon cycle varies largely depending on specific climate conditions and landscape characteristics. According to him, there are significant challenges in studying land and water systems at a relevant scale and detail to make accurate assessments.
“In order to advance the field, we need collaborative studies across scientific disciplines and approaches. Optimally, research infrastructures, funding, and educational programs should be designed to facilitate the integrated collaborative approaches needed,” says Jan Karlsson.
