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

Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina, USA,
Mammal Review (Impact Factor: 3.92). 10/2008; 39(1):33 - 52. DOI: 10.1111/j.1365-2907.2008.00136.x

ABSTRACT Twenty-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. 2. The 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 repro- ductive strategies are not well adapted to sustain high beaver population levels. 3. Our 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. 4. Based 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 compre- hension of the landscape context and natural history of the ecosystem being engineered. 5. We 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. Further- more, given the nature of the subantarctic landscape, streams will probably respond to restoration efforts more quickly than riparian ecosystems.


Available from: María Vanessa Lencinas, May 29, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Castor canadensis (american beaver) was introduced in the argentine sector of Tierra del Fuego in 1946 and has expanded into chilean territory, causing serious damage in rivers and riparian ecosystems. The beaver builds dams from Nothofagus tree material, mainly Nothofagus pumilio (lenga). After leaving the beaver dam, the forest ecosystem is transformed into an open meadow, featuring a full range of substrates, which can serve as microsites for seed germination and limited subsequent establishment of tree regeneration plants. The objective of this study was to analyze the establishment of lenga seedlings respect to microsites in a beaver meadow and in a forest unaffected by beaver. The research was conducted in an abandoned beaver dam in Vicuña, Tierra del Fuego (54°8'S, 68°42'W). The beaver dam was surrounded by an evenaged lenga forest (390 trees ha-1, 93.5 m2 ha-1). In the meadow of the abandoned beaver dam and in the forest were systematically installed 121 and 88 plots (1 m2), to estimate coverage for each of the substrates presents. At the ground level in the plots, microsites that are being used by seedlings of lenga were identified. Seedlings were dasometric characterized and the presence of signs browsing for Lama guanicoe (guanaco). The results showed that the main substrate in the meadow corresponded to sets of herbaceous plants (47.9 % coverage). In the forest the substrate at the ground level was covered mostly by herbaceous plants (30.7%) and litter (13.7 %). In the meadow were found 1.9 seedlings/m2. In the lenga forest is found 10.0 seedlings/m2. The most used microsites by seedlings the meadow was herbaceous plants litterand wood edge, and in the forest was decaying wood, branches and litter. 81.5% of the seedlings showed signs of browsing by guanaco in the meadow and only 15.9% of the seedlings in the forest.The restore abandoned beaver dams activities should consider to establish regeneration plants in microsites that are used naturally by lenga and recover the substrates for seed germination, in addition to isolate the presence of guanaco. Keywords: Plant regeneration, microsite, browsing, lenga, beaver meadow, Tierra del Fuego, Chile.
    09/2014, Degree: Ingeniero Forestal, Supervisor: Álvaro Promis
  • Revista Chilena de Historia Natural 12/2015; 88(1). DOI:10.1186/s40693-015-0034-6 · 0.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Novel assemblages of native and introduced species characterize a growing proportion of ecosystems worldwide. Some introduced species have contributed to extinctions, even extinction waves, spurring widespread efforts to eradicate or control them. We propose that trophic cascade theory offers insights into why introduced species sometimes become harmful, but in other cases stably coexist with natives and offer net benefits. Large predators commonly limit populations of potentially irruptive prey and mesopredators, both native and introduced. This top-down force influences a wide range of ecosystem processes that often enhance biodiversity. We argue that many species, regardless of their origin or priors, are allies for the retention and restoration of biodiversity in top-down regulated ecosystems. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Trends in Ecology & Evolution 02/2015; 30(3). DOI:10.1016/j.tree.2015.01.003 · 15.35 Impact Factor