A Spatially Explicit Population Viability Model using GIS: Insights to Dispersal

Population Viability Analysis (PVA) is a Monte Carlo simulation method for estimating the probability of extinction of threatened species. There has been a shift in the use of PVA from absolute species risk measurement to relative risk assessment associated with a ranking of management strategies. Furthermore, PVA models have sought to include more spatially explicit information, like habitat structure and dynamics. Geographical Information Systems (GIS) have long been used as a spatial decision support tool. More recently there has been particular interest in the integration of GIS with simulation modelling. Integrating PVA with GIS will enable us to explore spatially explicit management strategies, eg. habitat restoration or predator control in particular places. We describe a new individualbased, spatially explicit PVA model that integrates with the Environmental Systems Research Institute’s (ESRI) ArcView and ArcInfo GIS software. Environmental stochasticity is simulated in this model using normal or lognormal deviate random number generators. The model allows the user to choose from a variety of effects that environmental stochasticity and catastrophes have on fecundity and survival. The model simulates both sexes and allows for the Allee effect. This work is still in progress. We discuss the operation of this model and using preliminary data illustrate its application with a threatened species, the Yellow-footed Rock-wallaby (Petrogale xanthopus).