Landscape-level impact and habitat factors associated with invasive beaver distribution in Tierra del Fuego

Abstract

Understanding the amount of impact and distribution of invasive species is important for both basic ecological research and making management decisions. Because of their extensive impacts in southern Patagonia, invasive North American beavers (Castor canadensis) are considered both a scientific and conservation priority. However, little is known about the landscape-scale effects of these exotic ecosystem engineers. Using satellite imagery, we estimated the impact of beavers in the Argentine portion of Tierra del Fuego Island and determined the habitat factors (vegetation cover, forest type, stream presence and topography) related to their presence using both non-parametric statistical and information-theoretic approaches. Results indicated that more than 31,000 ha (1.6 % of the study area) were impacted by beavers and that the presence, but not the amount, of beaver impacts were spatially clustered. Impacts were greater in the Mountain ecoregion (2.8 % of the ecoregion) and lower in the Steppe (0.1 %). The best model for predicting beaver presence included variables related to water availability (presence of peatlands and streams), forage availability (forest type cover), and topography (slope and elevation). These findings support previous assertions that this invasion is the largest alteration to the sub-Antarctic forests in the Holocene. They also serve as a foundation for the development of maps based on habitat- and landscape-scale conditions to assist with the orientation of control, eradication, and restoration efforts currently being planned.