CURRENT STATUS OF INVASIVE BEAVER IN ARCHIPELAGO OF TIERRA DEL FUEGO: ARGENTINE AND CHILE BI-NATIONAL PERSPECTIVES

LIZARRALDE M,; WALLEM, P.; SCHIAVINI, ADRIÁN C.M.

Mendoza

Simposio; International Mammalogical Congress 10; 2009

CONICET- International federation of mammalogists, SAREM

Twenty-five pairs of North American beavers (Castor canadensis) were introduced in the Isla Grande de Tierra del Fuego (Argentina) in 1946. The founder population found optimal conditions given the absence of natural enemies and abundantavailability of resources, which facilitated its expansion and current invasion in the Southern Hemisphere. Beavers actualdistribution includes neighboring islands of Navarino, Hoste, Dawson, and recently the Chilean mainland at Brunswick Peninsula.They have colonized approximately 98% of the watersheds on Tierra del Fuego Island, with colony densities ranging from 0.2to 5.85 colonies/km2. This species is considered a keystone and archetype ecosystem engineer, due to the way it modifiesstream morphology and hydrology. For the Fueguian Archipelago this invasion constitutes one of the largest landscape-levelalteration of sub-Antarctic forests since the last ice age approximately 10.000 years ago; constituting a major managementproblem in southern regions of Patagonia. Large extends of riparian forests are being degraded and transformed into meadowswhich persist long after beaver abandoned them. On this basis, Argentina and Chile convened a Bi-National Strategy with thefuture vision of an ecosystem free of beaver also to protect and restore environments affected by them. At present experts ofboth countries are developing a program for beaver eradication and restoration of southern beech forests (Nothofagus sp.) ofPatagoniaFurthermore, given the nature of the subantarctic landscape, streams are expected to respond more quickly thanriparian ecosystems to restoration efforts.