Trade-offs between high class land and development: Recent and future pressures on Auckland's valuable soil resources

Sustainable land management is essential to meeting the global challenge of securing soil and water resources that can support an ever increasing population. In Auckland, New Zealand's largest city, population growth is forecast to increase from 1.5 to 2.5 million by 2040 which will put immense pressure on the region's soil resources. The objective of this study was to robustly quantify the amount of high class land (Land Use Capability Classes 1–3) that has been converted, and what is likely to occur, to urban development in Auckland using both long term trend records and future growth projections. Spatial analysis indicated that over the various spanning datasets 10,399 ha (or 8.3%) of Auckland's high class land has been converted to urban development through incremental urban extension, operative/approved greenfields and building consents. Of this, 10,080 ha of high class land was converted to development between the years, 1975 and 2012. The rate of urban extension onto high class land has accelerated since 1996. Furthermore, the majority of land allocated to urban extension since 1996 has been high class land. Looking into the near future, lodged/future greenfield developments equate to an additional potential development of 6010ha (or 4.8%) of current high class land. Future growth pressures indicate that this trade-off will continue. There is a real need to analyse the economic benefits and long term sustainability of future development against the protection of high class land for current and future production requirements. Further research should account for the true cost of lost provisioning, regulating and cultural soil ecosystem services to ensure that these values are recognised and considered not only by urban planners but also by both policy and decision makers.