A performance based consensus approach for predicting spatial extent of the Chinese windmill palm (Trachycarpus fortunei) in New Zealand under climate change

- Suitability maps predicting current and future distribution of Chinese Fan Palm Trachycarpus fortunei were developed
- Weighted ensembled maps using GLM, Maxent, RF and SVM for New Zealand produced for RCP 2.6, 4.5, 6.0, 8.5 trajectories
- Results show range expansion and centroid movement poleward and to higher elevations
- Greater suitability expansion and centroid movement change shown by higher gas concentration trajectories

The predicted distribution of the Chinese Windmill Palm (Trachycarpus fortunei) was modelled using several algorithms with inputs consisting of occurrence information and bioclimatic datasets. A global species distribution model was developed and projected into New Zealand to provide a visualization of suitability for the species in current and future conditions. To ensure model robustness, occurrence data was checked for redundancy, spatial auto-correlation and the environmental variables checked for cross-correlation and collinearity. The final maps predicting suitability resulted from ensembling the predictions of all the algorithms. The resulting ensembled maps were weighted based on the evaluation parameters AUC, Kappa and TSS. When reclassified into low, medium and high suitability categories, results show an expansion of high suitability areas accompanied by a reduction of low suitability areas for the species. The centroids of the high suitability areas also exhibit a general movement towards the Southwest under future climate conditions. The range expansion was proportional with the representative values of emission trajectories RCPs (2.5, 4.5, 6.0 and 8.5) used in projecting into future conditions. The movement magnitude and direction of predicted high suitability area centroids for the palm supports the use of the plant as an indicator of climate change.