Urban ecology in Christchurch: a reconciliation approach to enhancing native biodiversity on urban greyfields

Abstract

Traditionally New Zealand ecological research has focused on nature outside of cities, however, as with global trends, there is now more interest being given to the ecological functioning of cities and the potential they may hold for protecting native biodiversity. Traditionally, efforts to maintain biodiversity in urban areas have been restricted to remnants of native vegetation and restoration activities. Little attention has been given to how native biodiversity could be woven into the urban fabric in an ecologically meaningful way. One option, that is receiving much attention overseas, is to recruit underutilised urban spaces such as wasteland. A subset of urban wasteland, abandoned industrial areas usually awaiting development and other areas such as the railway buffer, are referred to here as greyfield. These are ephemeral sites that may sit between uses for as little as a few months to many years. Overseas, particularly in European countries, these have been recognised as important habitat for both native and introduced plant species. In New Zealand cities these support primarily introduced plants and their contribution to native biodiversity has been unknown. This thesis took an interdisciplinary approach to the question of whether urban greyfields might have potential value as biodiversity protection and conservation opportunity. Ecological methods were combined with an assessment of the planning framework to answer this question. iii Greyfields in Christchurch, New Zealand were surveyed to determine their current contribution to native biodiversity and whether they may act as urban analogues of natural habitats. Overseas research has shown that urban features such as pavements, walls and rooftops offer habitats analogous to cliffs and rocky habitats. Cities are therefore increasing the habitat exploitable by species whose natural habitats are geographically restricted. The Christchurch greyfields were assessed for their potential to act as analogues of four habitat types that have been categorised as historically rare in New Zealand: braided riverbeds, shingle beaches, rock outcrops and limestone outcrops. The findings suggest that urban greyfields, if managed appropriately, have the potential to support a wider range of native species Planning documents and biodiversity strategies written for Christchurch were assessed to see how well they facilitated non-traditional biodiversity enhancement initiatives, specifically the greyfield network for native biodiversity. A major finding here was a lack of information on how to enhance biodiversity where little of the natural features of the landscape were left and that this was creating a barrier to adopting more integrative approaches to enhancing native biodiversity. Finally, a plan to create a greyfield network for native biodiversity is proposed and suggestions are made as to minor changes to the planning framework that would more easily facilitate the uptake of novel biodiversity enhancement initiatives in the City.