Fences or Ferals? Benefits and Costs of Conservation Fencing in Australia

Abstract

One of the most intractable problems for the conservation of many species of native Australian vertebrates is predation from the introduced red fox Vulpes vulpes and feral house cat Felis catus. In recent years, increasing use has been made of conservation fences that exclude these introduced species and provide protection for large and viable populations of high-value native species within the fenced areas. Most conservation fences are constructed from wire mesh with a buried apron running along the base of the fence on both sides, with or without an overhanging top and wires that carry electrical charge. Experimental trials suggest that fences should be at least 1.8 m high with metal supports that discourage animals from climbing. Four main rationales appear to underpin the construction of conservation fences. These are to: (1) conserve small and relict populations of highly threatened species in situ; (2) use the newly-protected areas as sites to reintroduce rare or threatened species of mammals, birds or reptiles that once occurred there; (3) display native species within confined but natural surroundings for educational and ecotourism purposes; and (4) serve dual educational and research functions. The second rationale is the most common, and also provides excellent opportunities to study reintroduction protocols and the biology of the species involved. The success rate of vertebrates released into predator-free areas averages about 80%, whereas that for animals released into unprotected sites varies from 0 to 60%. Despite such manifest benefit to native vertebrates, conservation fences are costly to construct and maintain; managers must be constantly vigilant to detect and manage incursions of predators when they occur. An efficient approach should seek to minimise the long-term management costs of fences by balancing the capital expenses of secure designs against the costs of coping with more frequent failures. Conservation fences represent an acknowledgement that we are failing to successfully conserve biodiversity, but also buy us time to develop new tools to control introduced predators throughout the landscape. While research is under way, I suggest that fences could be made more cost-effective by extending their benefits to the broader region. This could be achieved by allowing otherwise confined prey species to move into and out of protected areas, and by improving their chances of survival outside the fences. Novel fence designs, changes to fence position, number and configuration in the landscape are needed for such broader benefits to be realised.