Prof Rich McDowell

Rethinking land use modelling

Land-use models commonly allocate land according to biophysical suitability, production potential and economic return. However, this framing can mistake land availability for the principal constraint while overlooking the demand, infrastructure and distribution systems that determine whether production achieves its intended outcome. We illustrate the need for a broader approach by asking whether New Zealand could become self-sufficient in food consumption. National consumption data for 2010–2023 and production and yield data for 2000–2024 were used to assess trends across OECD–FAO food groups and project demand and supply to 2045. We estimated the land required to address projected deficits, compared it with highly and moderately suitable land, and assessed the regional economic implications of land-use change. New Zealand produced more than it consumed for most food groups. Projected deficits were concentrated in cereals and legumes, nuts and seeds, with smaller fruit shortfalls; much of the cereal deficit arose from animal-feed demand rather than direct human consumption. The land and economic costs of closing these gaps were small, indicating that suitable land is unlikely to constrain greater food self-sufficiency. Instead, resilience depends more strongly on processing capacity, storage and distribution, market incentives, dietary demand and equitable access to nutritious food. These findings show why land-use modelling should move beyond identifying where production can occur. Models intended to inform food-system resilience should connect land allocation with demand, trade, infrastructure, accessibility and exposure to external shocks. Rethinking land-use modelling in this way changes both the questions asked and the interventions identified.