Climate Envelope Models (CEMs) use environmental variables such as temperature to match species distributions to their habitat. They have been widely used to understand and predict species’ behaviour under new environmental conditions, such as introduced species and range shifts under climate change. However, they have been widely criticised in recent years and there is growing enthusiasm to combine CEMs with demographic modelling techniques.

This is the focus of Jenny's PhD, using invasive succulents of the Crassulaceae family growing on Banks Peninsula, Canterbury as a case study. She hopes to use both CEMs and demographic models to explain what is driving the distribution of these species on Banks Peninsula, and predict any possible range expansion under climate change. She hopes that this study will contribute to developing new modelling tools for researchers and increase understanding of the behaviour of these local problematic species in order to better control their spread in New Zealand.

The first stage of her project is to map the current distribution of Crassulaceae across Banks Peninsula along with information on the size of populations and the habitat they occur in. She has used mostly road-based surveys to cover as much of the Peninsula as possible, with additional surveys conducted on rocky outcrops which are often prime habitat for these species. Along with additional distribution data collected from herbariums and previous independent surveys, she will use the data to run CEMs to predict suitable habitats for the species on Banks Peninsula. A second set of model runs will use native distribution data to do the same.

The later stages of the project will focus on analysing the predictive power of the CEMs at various spatial scales, and the integration of demographic models with CEM predictions to produce accurate predictions for current distributions and the impact of climate change on the species’ range.