Integrating Beaver Ponds into the Carbon Emission Budget of Boreal Aquatic Networks: A Case Study at the Watershed Scale

The ongoing recovery of beaver populations across the boreal biome of North America entails an increasing proliferation of beaver ponds in aquatic networks. Ecosystem-scale studies have demonstrated that beaver ponds are hotspots of carbon dioxide (CO2) and methane (CH4) production. However, beaver pond carbon (C) emissions have rarely been incorporated into estimates of inland water C budgets. Therefore, this potentially represents a major source of uncertainty for the C budget of the boreal biome. In this study, we combined a detailed geospatial analysis with measured CO2 and CH4 diffusive and ebullitive emission rates to estimate beaver pond total C emissions and incorporated these into a whole-aquatic network assessment. We carried out this study in a boreal watershed (13,105 km(2)) located in Quebec, Canada. Our results show that beaver ponds covered 77 km(2), representing 9% of the total aquatic surface area in the watershed. We estimate that beaver ponds contribute 7% of the total C emissions from the aquatic network and are responsible for 6% and 18% of the total CO2 and CH4 emitted annually, respectively. We project that by 2055, beaver pond CO2 and CH4 emissions for the same watershed may increase 17% and 56%, respectively, due to a combination of expanding beaver habitat and increasing temperatures. Our results highlight the role of beaver ponds not only in current aquatic CH4 emissions but also as a positive feedback loop for climate change, with significant radiative forcing potential given a scenario of climate warming and beaver population growth.