Lookout Creek in Oregon's H.J. Andrews Experimental Forest.
Theresa Hogue / Oregon State University
A new study has found that if the climate warms as projected, warmer streams could compound the effects of global warming by adding more heat-trapping carbon dioxide to the atmosphere.
Scientists tested the carbon output of streams at seven locations across the globe, including watersheds in Oregon, Puerto Rico, Alaska and Australia.
They monitored water temperature, dissolved oxygen and sunlight at the water surface and analyzed how all the organisms in the water were taking in carbon dioxide (CO2) during photosynthesis and releasing it during respiration.
They used that data to simulate how much more carbon dioxide streams would emit if their temperatures were warmer by 1 degree Celsius. Overall, they found that small increase in temperature resulted in a 24 percent increase in carbon dioxide emissions.
"It's a significant change," said study co-author Alba Argerich, who was a researcher at Oregon State University while the study was conducted. She now works at the University of Missouri. “Rivers respire like humans. In the future we should expect to find the streams are releasing more CO2 than what’s happening now.”
Argerich monitored McRae Creek and Lookout Creek in the H.J. Andrews Experimental Forest east of Eugene, Oregon, for the study, which was published this week in the journal Nature Geoscience.
She said not all streams will respond to warmer temperatures in the same way, and it was helpful to have numerous scientists taking the same measurements in streams across the globe to get a better idea of how much carbon dioxide could be released by warmer streams in the future.
“This paper confirms the role of streams as an active source of carbon dioxide in the atmosphere,” she said. “We haven’t put these numbers together until now, but they are exporting far more carbon than we were expecting. They are really active.”
Argerich said the new findings fill in a critical piece of missing information that can now be used to recalculate climate models.