Landscape-level effects of North American beavers in the Fuegian Archipelago: Is the introduction of beaver the largest threat to South America’s sub-Antarctic ecoregion in the Holocene?.

CH ANDERSON; P WALLEM; G MARTÍNEZ PASTUR; MV LENCINAS; MP SIMANONOK

Austin

Congreso; 96th ESA Annual Meeting; 2011

ESA

The sub-Antarctic ecoregion of southern South America not only hosts the world’s southernmost forests, but also the largest extent of temperate wetlands, forests and ice fields south of the equator. Additionally, is remoteness, with no latitudinal replica in the Southern Hemisphere, has kept it isolated from most modern environmental threats including nutrient deposition and habitat fragmentation, leading it to be declared one of the world’s last wilderness areas. Nonetheless, the globalized phenomenon of introduced species does affect this region, and today at the extreme southern tip – in the Fuegian Archipelago – the terrestrial mammalian assemblage is dominated by exotics 2:1. Among the introduced fauna, the North American beaver is believed to cause the largest impact to this landscape in the Holocene. To assess this assertion, we compared beaver’s effects on stream benthic taxa richness, assemblage and production in natural lotic (forested and grassland streams) and lentic (bogs, lakes) habitats and compared them to disturbed habitats (streams affected by forestry management, beaver ponds and beaver meadows). We evaluated this invasion at the habitat and landscape-scales by a) calculating the extent of invasion (% impacted stream length) and b) modeling natural and engineered landscapes with regards to diversity and ecosystem function.