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A worldwide study reveals rivers, lakes and reservoirs emit large quantities of carbon dioxide into the atmosphere when they dry up

Rivers, lakes and reservoirs emit large quantities of carbon dioxide into the atmosphere when these dry up, according to a new article published in the journal Nature Communications led by researchers of the University of Barcelona, the Catalan Water Research Institute (ICRA) and the Helmholtz-Center for Environmental Research in Germany (UFZ).

Decades ago, researchers observed that water ecosystems play an important role in the regulation of the cycle of carbon in the atmosphere. However, there are many issues to discover about this process. In the new study, twenty-four international research teams brought measurements from ecosystems from five continents -except for the Antarctica- framed within DryFlux, a global project in which the experts Biel Obrador and Daniel von Schiller, members of the Department of Evolutionary Biology, Ecology and Environmental Sciences and the research group Forestream (UB) take part.

An International project born in the Fluvià River

This new study joins the UB experts’ study on carbon cycle in dry water systems. According to the new study, “everything started in 2012, during a measure campaign in the Fluvià River while they studied the release of greenhouse gases in small dams in this river”, notes Biel Obrador, member of the Biodiversity Research Institute (IRBio) of the UB.

In collaboration with the experts Daniel von Schiller -member of the Water Research Institute (IdRA)- and Rafa Marcé (ICRA), they started the first studies which confirmed the release of large quantity of carbon dioxide even in dry areas of the river. “We wondered if this could be the case in other ecosystems in the world and if we were missing an important piece to understand the regulation of atmospheric carbon dioxide by ecosystems, notes Matthias Koschorreck (UFZ).

This is how DryFlux was born, a program on emission measurements in dry riverbeds at a global scale, “we were surprised by this very positive response, because although the methodology and equipment were relatively affordable for a research team, participating in field work has substantial costs, and each team had to take care of its own, we did not have the resources to cover all those expenses”, notes researcher Daniel von Schiller (UB-IdRA). Núria Catalán, expert from the United States Geological Survey, led the writing of the protocol for the study to make measurements of carbon dioxide emissions in dry riverbeds, lakes, and reservoirs.

A global phenomenon in rivers, lakes, and reservoirs worldwide

As a conclusion of the study, the experts found important carbon dioxide emissions from dry areas in freshwater ecosystems in all climate areas. “Therefore, this is a global phenomenon. If you take these emissions into account in today's global estimates for freshwater, your emissions are up six percent", says Phillipp Keller, doctoral researcher at the UFZ Lakes Research Department and first author of the study.

Everything suggests the mechanisms that cause the release of carbon dioxide in dry soils are the microorganism respiration processes. According to the experts, the factors causing the release of carbon dioxide are mainly the same worldwide.

“Our study shows that we still lack many pieces to fully understand the carbon dioxide cycle on a planetary scale, because there are many small gears that must be understood if we want to predict how ecosystems will respond to the current increase in carbon dioxide in the atmosphere”, says Biel Obrador.

“We hope that our work helps to ensure that dry areas of freshwater ecosystems are included in future calculations. With the progression of climate change and human impacts, freshwaters will dry up more and more frequently in large regions of the planet, and some of them forever, such as the Aral Sea in Central Asia. Therefore, emissions from dry freshwaters will only increase", concludes Obrador.