Get access

Do introduced North American beavers Castor canadensis engineer differently in southern South America? An overview with implications for restoration

Authors

  • CHRISTOPHER B. ANDERSON,

    Corresponding author
    1. Conservation and Society Group, Millennium Institute of Ecology and Biodiversity, Casilla 653, Santiago, Chile,
    2. Omora Ethnobotanical Park, University of Magallanes, Puerto Williams, Chile;
    Search for more papers by this author
  • GUILLERMO MARTÍNEZ PASTUR,

    1. Forest Resources Laboratory, Centro Austral de Investigaciones Científicas (CADIC-CONICET), Ushuaia, Tierra del Fuego, Argentina;
    Search for more papers by this author
  • MARÍA VANESSA LENCINAS,

    1. Forest Resources Laboratory, Centro Austral de Investigaciones Científicas (CADIC-CONICET), Ushuaia, Tierra del Fuego, Argentina;
    Search for more papers by this author
  • PETRA K. WALLEM,

    1. Center for Advanced Studies in Ecology and Biodiversity, Pontificia Universidad Católica, Santiago, Chile;
    Search for more papers by this author
  • MICHELLE C. MOORMAN,

    1. Omora Ethnobotanical Park, University of Magallanes, Puerto Williams, Chile;
    2. Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina, USA,
    Search for more papers by this author
  • AMY D. ROSEMOND

    1. Odum School of Ecology, University of Georgia, Athens, Georgia, USA
    Search for more papers by this author

  • Editor: AS

C. B. Anderson E-mail: canderson@alumni.unc.edu

ABSTRACT

  • 1Twenty-five pairs of North American beavers Castor canadensis Kuhl were introduced to Tierra del Fuego Island in 1946. The population has expanded across the archipelago, arriving at the Chilean mainland by the mid-1990s. Densities range principally between 0.5–2.05 colonies/km. They have an impact on between 30–50% of stream length and occupy 2–15% of landscape area with impoundments and meadows. Beaver impacts constitute the largest landscape-level alteration in subantarctic forests since the last ice age.
  • 2The colonization pattern, colony densities and impacted area indicate that habitat in the austral archipelago is optimal for beaver invasion, due to low predator pressure and suitable food resources. Nothofagus pumilio forests are particularly appropriate habitat, but a more recent invasion is occurring in adjacent steppe ecosystems. Nonetheless, Nothofagus reproductive strategies are not well adapted to sustain high beaver population levels.
  • 3Our assessment shows that at the patch-scale in stream and riparian ecosystems, the direction and magnitude of exotic beaver impacts are predictable from expectations derived from North American studies, relating ecosystem engineering with underlying ecological mechanisms such as the relationships of habitat heterogeneity and productivity on species richness and ecosystem function.
  • 4Based on data from the species' native and exotic range, our ability to predict the effects of beavers is based on: (i) understanding the ecological relationships of its engineering effects on habitat, trophic dynamics and disturbance regimes, and (ii) having an adequate comprehension of the landscape context and natural history of the ecosystem being engineered.
  • 5We conclude that beaver eradication strategies and subsequent ecosystem restoration efforts, currently being considered in southern Chile and Argentina, should focus on the ecology of native ecosystems rather than the biology of this invasive species per se. Furthermore, given the nature of the subantarctic landscape, streams will probably respond to restoration efforts more quickly than riparian ecosystems.

Ancillary