DO INTRODUCED NORTH AMERICAN BEAVERS ENGINEER DIFFERENTLY IN SOUTHERN SOUTH AMERICA? – AN OVERVIEW WITH IMPLICATIONS FOR RESTORATION

ANDERSON, CB; MARTÍNEZ PASTUR, G; LENCINAS, MV; WALLEM, P; MOORMAN, MC

Mendoza, Argentina

Congreso; X International Congress of Mammalogy; 2009

North American beavers (Castor canadensis) were introduced to Tierra del Fuego Island in 1946 and since have expanded across the archipelago and the after the '90s across the Chilean mainland (Brunswick Peninsula). As ecosystem engineers, beavers have large impacts on terrestrial and aquatic ecosystems in their native and introduced habitats. However, while in their native range, beaver ponds may constitute a unique landscape feature, in Tierra del Fuego such beaver-mediated ponds may simply replicate natural lentic ecosystems. Additionally, Northern Hemisphere vegetation presents adaptations to beaver herbivory, while the riparian vegetation of sub-Antarctic forests has no similar experience to beaver engineering in its evolutionary history. By reviewing the literature for both biomes, we answered the following questions: Are the directions and magnitudes of change caused by beavers the same in North and South America? Are the mechanisms by which beavers alter the environment and the resulting ecological responses the same between riparian and aquatic ecosystems? Based on current understanding of the habitat-level impacts of beavers in terrestrial and aquatic ecosystems of the austral archipelago, we found that the direction and overall extent of their effects were predictable based on expectations from their native distribution. A comparison of beaver impacts in both terrestrial and aquatic ecosystems in the Fuegian Archipelago, suggests that the consequences and persistence are greater in the riparian zones than in stream ecosystems, given the lack of regenerative strategies of plants to these disturbances. Thus to achieve restoration after controlling beaver expansion, the proposed activities must be carried out within the context of whole ecosystem management at the watershed level and with long-term commitment. Besides poorly implemented control programs may have an adverse effect on riparian vegetation, with large direct and indirect impacts.