Ecological Implications of Exurban Development:udThe effects of people, pets and paddocks on avian and mammalian wildlife

摘要

Broad-acre subdivisions on the fringe of cities constitute a relatively novel and rapidly increasing form of urban development known as exurbia. Despite the potentially significant effects exurban development can have on nature, no study has documented its effects on the distinct faunal communities of Australia. Within two exurban regions of Hobart, Tasmania, Australia, birds were sampled within discrete exurban habitats, exurban forest, modified forest, gardens, and paddocks, and corresponding wildland forests. Flightless mammals were surveyed by spotlight in the same environments. Landowners gave their opinions on a variety of nature-related issues. Their ownership of domestic mesopredators, participation in activities that might affect wildlife, and observations of wildlife were also recorded. Wildland bird species assemblages persisted within exurbia where the native canopy remained, but were displaced by synanthropes in gardens, and were strongly disadvantaged in paddocks. An aggressive small-bird-excluding edge species, the noisy miner, responded more strongly to historic rural clearance boundaries than to forest perforation and modification. In its absence, avian habitat specialists were not affected by the proximity or density of houses. Paddocks had more heterogeneous bird assemblages than expected. Overall, the native exurban avifauna was richer than the avifauna of both adjacent suburbs and control areas of native vegetation. Exurban landowners were comprised of four discrete attitudinal groups. Two of the groups were nature lovers, one was utilitarian, and the other was fearful of aspects of nature beyond their control, particularly unruly trees. The group with the strongest fear of trees had the highest level of tree cover on their property.udAttitudinal group was also associated with the distribution of some garden types, but not with landscape characteristics. Exurbanite attitudinal type had very little influence on the frequency or distribution of wild mammals observed by spotlight, but nature lovers were more likely to report observations of some species. Independent of attitudinal groups, the most detrimental landowner activity was pet ownership. Any detrimental effects of exurban domestic cat populations were unapparent due to the non-uniform distribution of cat owners and the presence of feral cats. Properties with dogs, however, were distributed more uniformly, and were avoided spatially and temporally by several species of mammal, including species that dog owners had not observed as prey. Within an isolated peninsula exurban region, the spatial avoidance of exurbia resulted in low numbers of those mammal species with large home range requirements. One species of bandicoot, however, was more common where houses were relatively dense. Overall, two very fecund mammal species, including a threatened native bandicoot, were more abundant in exurbia than in wildlands. For mammal conservation, houses may best be clustered in areas where access to wildland remnants is limited. This will slightly diminish the mammalian species diversity where residents live, but may be preferable to dispersed housing developments, which support greater species diversity than clustered developments, but will also distribute the effects of domestic mesopredators over a greater proportion of the landscape. Heterogeneous exurban landscapes are not necessarily detrimental for avifaunal conservation, as long as they include areas of undisturbed native vegetation, either in remnants or on exurban properties.