Author:Mehrnaz Rohani, Gerda Kuschel
Source:Auckland Council Research and Evaluation Unit, RIMU
Topics:Land useAir qualityCapacity for growthDemographics and societyFreshwaterSoilEnvironmentEconomy, business and industry
Auckland’s sustained population growth and its projected future growth, puts pressure on the natural environment. The concentration of people living in one particular area requires resources – land, water, energy, infrastructure and material flows. Economic efficiencies can be made through concentrating large numbers of people who live and work in urban areas, but resource flows also create waste streams and require the conversion of natural or rural land to built form.
Spatial policy and urban planning provide a bird’s-eye view of future urban form. They provide a means of exploring scenarios and thinking about how the future might unfold, and how the urban footprint might evolve. The environmental effects of the future urban form are seldom represented in spatial plans. Nevertheless, there is agreement that urban growth impacts on air quality, water bodies and fertile soils. This has implications for human health and the health of terrestrial and marine ecosystems.
To understand the impact of different future urban forms on the natural environment this study compares the impact of three different urban form scenarios. By keeping total population and employment growth fixed out to the year 2046, this report explores the differences in impacts on the natural environment associated with differing urban development scenarios. A ‘baseline scenario’ urban form, based on up to date (as at December 2016) population and household growth projections used by Auckland Council, is developed. Two alternative growth distribution scenarios are subsequently developed; one where growth is concentrated into a smaller geographical area (‘intensive’ scenario) and another that distributes growth in a more dispersed and land-extensive form (‘expansive’ scenario).
A method to assess the potential impact of the three Auckland urban form scenarios on air quality,water bodies and fertile soil was developed. It is termed a ‘value transfer’ methodology, which is often used in other studies to estimate economic values of ecosystems and difficult to measure environmental effects. The value transfer method used the best available existing information from reliable completed New Zealand studies to measure and monetise each scenario. A value transfer method is appropriate to use in the context of urban form scenarios, as data is not always available on site-specific effects of future growth, yet data that has been previously observed in studies in a similar context, can be used to inform the likely effects.
Auckland Council technical report, TR2017/022