Biodiversity outcomes of an urban revegetation programme in Wellington, New Zealand: The role of patch size, isolation, age and the urban matrix
Urban revegetation programmes are an important contribution to the biodiversity of our landscape environment. Wellington city has, for nearly two decades, promoted revegetation of the city with a focus in latter years on eco-sourced native species. This is a substantial urban greening project planting 100,000 native plants per annum. This thesis analyses the native revegetation programme and posits recommendations for continuance and enhancement for consideration. Data were collected from a sample set of twenty revegetated sites and four reference sites in Wellington city. Two transects per site were set up with invertebrate pitfall traps, lizard pitfall traps, lizard tree covers, bird count stations and vegetation surveys. The data were collected over a twelve-month period. Ordination was used to examine the community composition of revegetation sites in relation to each other and the four reference sites. Multiple regression was used to examine the influence of patch age, patch size, isolation and residential land cover upon a range of biodiversity variables. The key findings of this study are that revegetated sites lacked the level of ground cover by native seedlings that were characteristic of the mature reference sites. Also found was that revegetation sites in Wellington City require around ten years of growth before natural regeneration of native seedlings began to become apparent. Large native birds were more likely to be found in close proximity to mature primary bush, confirming that mature primary bush is an essential element of the landscape. Weta were found in increased numbers as distance from mature primary bush increased. Northern grass skinks were the only species of lizard found, in association with a higher proportion of residential area in the matrix. The key management recommendations of this study are; the development of a collaborative connective strategy; further enrichment planting designed to maximize structural diversity over time; the investment in well planned robust monitoring programmes. This research contributes to the understanding of biodiversity outcomes of an urban native revegtation programme, providing baseline data for future monitoring purposes.