Native vertebrate herbivores facilitate native plant dominance in old fields while preventing native tree invasion - implications for threatened species

In a world in which reconstruction of the ‘natural’ does not necessarily result in the best outcomes for biodiversity, it is important to consider the implications of management change on faunal populations in protected areas, and on the future of the species that are most in need of protecting. On the old fields of Maria Island National Park, Tasmania we use vegetation data from exclosure plots and adjacent controls to reveal that current populations of native vertebrate herbivores prevent tree and shrub invasion of marsupial lawns and reduce the abundance of introduced plants. This maintenance of marsupial lawns may be less effective after an insurance population of the endangered marsupial carnivore, the Tasmanian Devil Sarcophilus harrisii, is introduced to the island. Native vertebrate herbivores represent potential prey for the devils, impacting on grazing regimes and plant succession. Vegetation change is most likely to favour two threatened bird species, while reducing the prospects for the threatened Tasmanian Devil and potentially threatened Tasmanian Pademelon Thylogale billardierii.