| | Recharging groundwater, maintaining water quality, providing habitat. Those are just a few of the societal benefits from wetlands. Now a prairie-wide initiative is collecting data that could add yet another benefit to the list—carbon storage.
Called the Agriculture and Wetlands Greenhouse Gas Initiative, its main goals are “to provide the first numbers for carbon sequestration and greenhouse gas emissions for prairie pothole wetland systems, and to relate those numbers to the practices in the uplands around the wetlands,” explains Dr. Rhonda McDougal, a research scientist with Ducks Unlimited Canada (DUC).
McDougal is coordinating this multi-agency, multidisciplinary initiative, which began in 2002. The results will help in painting a more complete picture of the nation’s greenhouse gas emissions needed for Canada’s international negotiations and in identifying agricultural practices that reduce emissions.
“Wetlands have always been part of the natural greenhouse effect and part of the carbon cycle balance,” explains McDougal. Like other plants, wetland plants lock up carbon in their tissues while they live. But dead plant matter at the bottom of a prairie pothole wetland can take a long time to decompose and release the carbon. That’s because the sediments in pothole wetlands are typically anaerobic (oxygen-free), and oxygen is necessary for decomposition. As well, microbes involved in decomposing organic matter are inactive for about eight months of the year on the prairies because of the cold temperatures. Along with storing carbon, wetlands can also emit carbon in the form of methane under some conditions because some types of microbes adapted to anaerobic environments release methane.
The initiative, composed of five interlinked projects, is measuring organic carbon in soil and wetland sediments, and measuring emissions of methane, nitrous oxide and carbon dioxide. McDougal says, “One of the challenges for prairie wetlands is that no one has measured greenhouse gas emissions from them before. We don’t have tried and true methods for sampling.”
The researchers are monitoring about 100 wetlands over at least five years, as water levels and temperatures fluctuate with annual and seasonal variations. The sites represent a range of soil zones, climatic conditions and agricultural practices. McDougal says, “With a wetland, anything happening in the surrounding upland comes downhill and impacts that wetland. So we do our sampling in a transect that runs from the upland, whether it’s an agricultural field or a grassland, down through the zone of cattails and willows, and then through basin and up the other side.”
Along with monitoring individual wetlands, the researchers are also using flux towers to collect emission “footprints” from larger areas. In other Canadian studies, airplanes fitted with greenhouse gas sensors are attempting to collect emissions from entire regions. These three scales of measurement need to be brought together to create regional and national emission inventories.
McDougal hopes the initiative’s results will play a part in helping people adapt to the very serious impacts resulting from climate change over the coming decades. She says, “Climate change has already been happening for years, and it’s accelerating. And we need to do so much more to understand it and to cope. It’s going to be a question of learning how to cope with global rates of change in ecosystems that have never happened before in human experience.” |
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