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 (CO 2 ) and methane (CH 4 ) 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 CO 2 and CH 4 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 Québec, 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 CO 2 and CH 4 emitted annually, respectively. We project that by 2055, beaver pond CO 2 and CH 4 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 CH 4 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.