Abstract
Urban biodiversity is often underappreciated, despite providing many ecosystem services vital to human health and helping promote environmental awareness. The adverse effects of urban sprawl have caused scientists and policymakers to believe that densifying urban development is critical to help diminish processes of ecological degradation. Under the National Policy Statement for Urban Development 2020, New Zealand is moving towards enforcing higher-density housing in areas with good access to services, public transport networks and infrastructure. Intensification policies create an opportunity to improve urban biodiversity by avoiding land fragmentation and altering native species composition while addressing the rising requirements for urban housing supply throughout the country.
In this research, nine housing developments throughout Auckland, Christchurch, and Dunedin were examined to determine how New Zealand local authorities, policymakers and property developers can help support biodiversity in urban residential areas. A literature review, model ecological tool, policy analysis and key informant interviews were used to address the following research questions; What impact will medium-density housing have on New Zealand’s urban ecosystems? How can medium density housing be improved to support urban biodiversity within New Zealand? What provisions exist to implement and enhance indigenous vegetation in residential developments within New Zealand’s current formal planning framework? And are there any measures in proposed future New Zealand planning instruments to improve biodiversity in residential areas?
The primary findings indicated that medium-density residential developments have more abundance and a larger range of native species planted within the site than low-density subdivisions. Developments with a site design that applied initial biodiversity values had higher vegetation quality comparatively. Stormwater swales and drains had the largest use and clustering of native vegetation in nearly all sites. All developments resulted in green space loss compared to their original use, although most case studies improved the quality of vegetation present. In addition, Earthsong Eco-Neighbourhood and other international best-practice examples demonstrated that removing private vehicle infrastructure significantly increased vegetative cover. The findings also suggest that the overwhelming focus on protecting ‘significant’ ecological areas in New Zealand has led to no specific policies or rules requiring urban residential areas to incorporate indigenous vegetation and enhance biodiversity. However, policies in the proposed National Policy Statement for Indigenous Biodiversity could force local authorities to take action to ensure all urban environments have at least 10% of indigenous vegetation cover in the near future.
The study suggests that policymakers and local authorities should create specific policies, rules, and incentives on a district plan level to encourage residential properties to incorporate indigenous vegetation cover and enhance local biodiversity. Meanwhile, developers and designers need to greatly reduce car infrastructure, preserve maximum levels of permeable space, incorporate more semi-permeable paving to allow flexibility for vegetation and run-off, as well as creating corridors to adjacent vegetation while providing high-quality greenspace for residents on-site to enable their connection to nature close to home within an urban setting.