Exploring Greenhouse Gas Emissions from Beaver Ponds in Southern Rhode Island

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Senior Honors Projects

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http://digitalcommons.uri.edu/srhonorsprog/328; http://digitalcommons.uri.edu/context/srhonorsprog/article/1342/type/native/viewcontent
Welsh, Molly K
Climate change; greenhouse gases; beaver ponds; Rhode Island; Climate change; greenhouse gases; beaver ponds; Rhode Island; Biogeochemistry; Hydrology
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Climate change is one of the largest environmental issues facing humanity today, having the potential to alter fresh water availability, agricultural yields, forest productivity, and global sea levels. As climate change is likely to increase the intensity of extreme weather events, the potential for massive human and financial consequences is of further concern. The Intergovernmental Panel on Climate Change asserts that climate change is due to anthropogenic alterations of the atmosphere’s composition, with additional contributions from natural biochemical processes. In particular, the rapid increase in the concentrations of greenhouse gases (GHGs) in the atmosphere can trigger atmospheric warming as these GHGs absorb the heat radiated from the earth and re-emit it into the atmosphere. Much research has been directed at understanding the sources of GHGs to better assess how to reduce GHG emission rates. The study of biogeochemical cycling, particularly the cycling of carbon (C) and nitrogen (N), underlies our ability to predict GHG generation from natural environments. More scientific research is necessary to accurately derive estimates of GHG emission rates from different landscapes around the globe. These estimates will subsequently inform decisions in GHG management and climate change mitigation. Research to date has indicated that certain landscape features may function as “hotspots” for GHG emissions. Because it is estimated that natural wetlands account for nearly 30% of total methane emissions (Reddy and DeLaune 2008), it is important to better quantify the fluxes of methane and other GHGs from natural environments into the atmosphere. Studies (Naiman et al. 1994, Soumis et. al 2004) have shown that wetland environments, such as beaver ponds, may be sources of atmospheric carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) – all potent GHGs. Due to the resurgence of the North American beaver (Castor canadensis), there is an increasing interest in investigating beaver ponds as potential hotspots of GHG emission. Beaver dams impound natural stream flow, creating wetland environments that foster anaerobic conditions, trap sediments and nutrients, and accumulate organic matter. This organic matter serves as a C source for microbial activity to facilitate biogeochemical cycling. With these conditions, beaver ponds alter the cycling of C and N within the riverine environment via the processes of respiration, methanogenesis and denitrification (Naiman et al. 1994) – which generate CO2, CH4 and N2O. In this study, the diffusive flux of GHGs (CO2,CH4, N2O) from the air-water interface of three beaver ponds in Southern Rhode Island in