A mathematical model to predict the long-term effects of herbivory on vegetation cover and biodiversity in the South Australian rangelands
(J Boland,, L McArthur and F Tiver)
In previous research and other literature sources it is shown that
herbivores, particularly introduced ones such as sheep and rabbits, have
reduced the levels of regeneration of a number of species of native
trees and shrubs in the arid rangelands of southern Australia since
European settlement. These reduced levels of regeneration mean that
populations of some species are declining whilst others less palatable
to herbivores are being maintained, hence gradually altering the
composition and/or overall cover of vegetation.
In the long term, this could result in loss of palatable species valuable to the pastoral industry for animal production, and/or the dominance of large areas by undesirable “woody weed” species. The loss or reduction in cover of a number of tree and shrub species is not only a significant loss of biodiversity alone, but as in all ecosystems, the habitat and resource loss caused by removal of the important structural dominants may result in reduced biodiversity of other organisms in the system such as birds and small mammals which are dependent on the plants for food and shelter. This could result in reduced value of the land for biodiversity and conservation.
The aim of this research is to develop an “individual oriented” mathematical model with the ability to process the existing data, and other literature evidence on regeneration levels under grazing of a range of tree and shrub species in the arid zone of southern Australia. The model should be capable of predicting the long-term outcomes for biodiversity and native vegetation cover under various herbivores and grazing regimes, and provide a valuable tool for rangeland livestock and conservation management.