Modelling Continuous Location Suitability Scores and Spatial Footprint of Apple and Kiwifruit in New Zealand

Abstract

Under climate change, land use suitability for horticultural production will change; this has prospects of both adverse socio-economic impacts for the industry in some regions, and beneficial impacts in others. Policy development and industry guidance are needed to develop adaptations to mitigate climate change risks and exploit new opportunities. For climate-change issues, models provide a powerful means for assessing future suitability at a patch, region or national scale in order to guide policy decisions. Here, we describe the development of a new continuous (sliding-scale) suitability modelling approach to assess the suitability of different locations for growing apple and kiwifruit in New Zealand, based on phenological and physiological considerations; these models used geographical information system (GIS) soil, land and weather data to develop maps showing the suitability of locations across New Zealand for cultivating apple and kiwifruit. The models were “ground-truthed” in an iterative process of expert parameterisation and recalibration to ensure maps aligned with current growing locations for the two crops. We estimated an econometric logit model that incorporated the continuous suitability scores as predictors of land use for apple and kiwifruit. Comparison of modelled suitability scores with industry-supplied maps of apple and kiwifruit orchards showed good consistency between predicted suitability and current land use. Compared with a range of alternative land uses, suitability for apple was highest for locations currently used to grow apple and suitability for kiwifruit was highest for locations currently used to grow kiwifruit. Our framework provides the capability to project incremental changes in the suitability of locations for apple and kiwifruit under different climate change pathways and to project consequential changes in their spatial footprints; this framework can be extended to other crops.