Modelling the Spread of European Buckthorn in the Region of Waterloo

Abstract

European buckthorn (Rhamnus cathartica L.) is a common invasive species in the Region of Waterloo. Management of buckthorn is expensive and time consuming and as a result it has continued to spread in the Region of Waterloo despite being on the Ontario noxious weed list. Control of buckthorn will require long term management to prevent reinvasion of managed areas. Therefore this project seeks to provide land managers with a model to predict the likely spread of buckthorn over time and space so that the cost of management can be predicted and different management strategies can be compared. A generalized linear mixed-effects model was used to create a habitat suitability model and a spread model for the probability of buckthorn presence for cells in a grid. The habitat suitability model predicts the presence of buckthorn based on environmental characteristics while the spread model predicts the likelihood of buckthorn invasion based on the suitability of habitat and the presence of buckthorn in the surrounding area. The spread model indicates that the invasion of buckthorn is influenced by the suitability of habitat and the presence of buckthorn in neighbouring cells. The success of the spread model suggests that this approach can be used to create a spatiotemporally explicit model with limited sampling effort. To explore the utility of the spread model for conservation management purposes, a simulation model was created that is based on the spread model. Simulations were performed to test the spread of buckthorn in a sample forest patch and to test different management strategies. The simulations showed that buckthorn can be controlled within a patch with a limited amount of effort.