Abstract
Beavers are influential ecosystem engineers in aquatic ecosystems, but were exterminated in Sweden in the 1800s. Reintroduced in the 1920s, beavers have recolonized most of Sweden, with profound effects at local and landscape scales. Our project BABI will investigate whether beaver dam impoundments constitute new *hotspots* not only for biodiversity, ecosystem retentivity and ecosystem functioning, but also for methylation and bioaccumulation of mercury in biota. Additionally, BABI evaluates if the effects of beavers conflict with Swedish environmental objectives, and with the reference classification schemes of the Water Framework Directive. BABI will be performed at two spatial scales. At the local scale, beaver effects on water and sediment chemistry, community composition and diversity, and ecosystem functioning will be quantified in 14 beaver affected and six reference systems over three years using state-of-the-art methods. At the landscape scale, BABI evaluates the biogeochemical and ecological impact of beavers within historic, present and future scenarios of species distribution and population density, with GIS-methods used to upscale empirical data. BABI thus constitutes the first integrated investigation of the biogeochemical and ecological effects of beavers, conducted at multiple scales. Considering both the potential positive and negative effects of beaver dams, BABI will provide scientific data crucial for management as beavers continue to expand in Europe.
Sweden