NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The European Rabbit Oryctolagus cuniculus was successfully introduced into Australia in 1858. It has since spread broadly across the southern two thirds of the continent, and its area of occupancy is now approximately 4.5 million square kilometres (Myers et al. 1989).
2. Feral rabbits occupy a wide range of habitats, including native and modified grasslands, woodland, heath and forest, and can achieve high densities in some agricultural and suburban areas. Unlike the domesticated rabbit, which is not the subject of this determination, feral rabbits exhibit minimal or no dependence on humans to meet their ecological requirements.
3. There is evidence that feral rabbits impact negatively on indigenous species via competition for resources, alteration of the structure and composition of vegetation, and land degradation. Competition and land degradation by feral rabbits is listed as a Key Threatening Process on Schedule 3 of the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.
4. Feral rabbits are grazers that prefer green grass and herbage. They may also feed on seeds and browse and, during drought, the bark and roots of shrubs. Several indigenous species overlap in diet with the feral rabbit, and are impacted negatively by competition for food with the feral rabbit. Threatened species that suffer in dietary competition with the feral rabbit include the Yellow-footed Rock-wallaby Petrogale xanthopus, Brush-tailed Rock-wallaby Petrogale penicillata and Southern Hairy-nosed Wombat Lasiorhinus latifrons (Dawson & Ellis 1979, 1984; St John 1989; Short & Milkovits 1990). The Plains Wanderer Pedionomus torquatus and Malleefowl Leipoa ocellata also appear to be adversely affected by the feral rabbit, through competition for food and/or by alteration and reduction of suitable habitat (Baker-Gabb 1990; Garnett 1992).
5. Grazing by feral rabbits reduces survival and recruitment of several species of threatened plants. These include Acacia carneorum, Grevillea kennedyana, Cynanchum elegans, Thesium australe and Lepidium hyssopifolium (Cropper 1987; Auld 1990, 1993; Griffith 1992; Matthes & Nash 1993). Grazing by feral rabbits appears also to have marked effects on the structure and composition of vegetation communities in many areas (Williams et al. 1995), and a number of Endangered Ecological Communities including the Acacia loderi Endangered Ecological Community.
6. Grazing by feral rabbits could cause species, populations or ecological communities that are not threatened to become threatened. A number of long-lived tree and shrub species have their recruitment prevented or severely limited by rabbit grazing in arid and semi-arid Australia, including NSW (Crisp and Lange 1976; Lange and Graham 1983; Chesterfield and Parsons 1985; Auld 1990; 1993; 1995a, 1995b; Woodell 1990; Pickard 1991; Tiver and Andrew 1997, Auld and Denham 2001). Continued rabbit impacts could cause some of these species (or populations of them) to become threatened, while where they are community dominants the ecological community may become threatened. Examples include Acacia spp; Hakea spp., Callitris gracilis, and communities of belah/rosewood (Casuarina pauper/Alectryon olefolius) and western Myall, Acacia pendula.
7. By removing above-ground and below-ground vegetation, feral rabbits contribute to erosion and loss of topsoil by wind and rain. This form of land degradation reduces the chance of successful establishment of indigenous plants, and increases the susceptibility of many indigenous vertebrates to predation from feral predators (Morton 1990; Dickman 1993).
8. Feral rabbits are eaten by introduced predators such as red foxes Vulpes vulpes and feral cats Felis catus, and can maintain populations of these species at artificially high levels. Dietary switching of these predators from rabbits to indigenous species can occur following declines in rabbit populations, such as those caused by rabbit calicivirus disease, causing 'hyper-predation' impacts on indigenous species (Dickman 1996; Newsome et al. 1997). A Threat Abatement Plan to manage Competition and grazing by the Feral European Rabbit Oryctolagus cuniculus (L.) should therefore be integrated with management of introduced predators.
9. In view of points 3, 4, 5, 6, 7 and 8 above, the Scientific Committee is of the opinion that Competition and grazing by the feral European Rabbit Oryctolagus cuniculus adversely affects two or more threatened species, populations or ecological communities or could cause species, populations or ecological communities that are not threatened to become threatened.
Proposed Gazettal date: 10/05/02
Exhibition period: 10/05/02 - 14/06/02
Reference:
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