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A city’s planted trees, the great majority of which are in private gardens, play a fundamental role in shaping a city’s wild ecology, ecosystem functioning, and ecosystem services. However, studying tree diversity across a city’s many thousands of separate private gardens is logistically challenging. After the disastrous 2010–2011 earthquakes in Christchurch, New Zealand, over 7,000 homes were abandoned and a botanical survey of these gardens was contracted by the Government’s Canterbury Earthquake Recovery Authority (CERA) prior to buildings being demolished. This unprecedented access to private gardens across the 443.9 hectares ‘Residential Red Zone’ area of eastern Christchurch is a unique opportunity to explore the composition of trees in private gardens across a large area of a New Zealand city. We analysed these survey data to describe the effects of housing age, socio-economics, human population density, and general soil quality, on tree abundance, species richness, and the proportion of indigenous and exotic species. We found that while most of the tree species were exotic, about half of the individual trees were local native species. There is an increasing realisation of the native tree species values among Christchurch citizens and gardens in more recent areas of housing had a higher proportion of smaller/younger native trees. However, the same sites had proportionately more exotic trees, by species and individuals, amongst their larger planted trees than older areas of housing. The majority of the species, and individuals, of the larger (≥10 cm DBH) trees planted in gardens still tend to be exotic species. In newer suburbs, gardens in wealthy areas had more native trees than gardens from poorer areas, while in older suburbs, poorer areas had more native big trees than wealthy areas. In combination, these describe, in detail unparalleled for at least in New Zealand, how the tree infrastructure of the city varies in space and time. This lays the groundwork for better understanding of how wildlife distribution and abundance, wild plant regeneration, and ecosystem services, are affected by the city’s trees.
This paper analyses the city of Christchurch, New Zealand, which has been through dramatic changes since it was struck by a series of earthquakes of different intensities between 2010 and 2011. The objective is to develop a deeper understanding of resilience by looking at changes in green and grey infrastructures. The study can be helpful to reveal a way of doing comparative analysis using resilience as a theoretical framework. In this way, it might be possible to assess the blueprint of future master plans by considering how important the interplay between green and grey infrastructure is for the resilience capacity of cities.
Photograph captioned by BeckerFraserPhotos, "A view of Hereford Street, looking west from number 92".
A photograph captioned by BeckerFraserPhotos, "The McKenzie & Willis building on Tuam Street. The building next door to it has suffered more damage from the 23 December 2011 earthquake".
Photograph captioned by BeckerFraserPhotos, "Worcester Street - damaged Warners Hotel end wall".
Photograph captioned by BeckerFraserPhotos, "Armagh Street (north side) looking towards Madras Street. The TUC building to be demolished. It has slumped badly due to liquefaction".
Photograph captioned by BeckerFraserPhotos, "Hereford Street/Latimer Square corner - A computer monitor on the footpath".
A photograph captioned by BeckerFraserPhotos, "A brick building on Lichfield Street which has suffered further damage during the 23 December 2011 earthquake".
A photograph of a list of building occupants, captioned by BeckerFraserPhotos, "A notice board at 209 Tuam Street".
A photograph captioned by BeckerFraserPhotos, "The Hotel Grand Chancellor, demolished to a level that it no longer dominates the skyline".
A photograph captioned by BeckerFraserPhotos, "The partially-demolished Hotel Grand Chancellor on Cashel Street".
Photograph captioned by BeckerFraserPhotos, "A detail of the former Public Library on Hereford Street".
Photograph captioned by BeckerFraserPhotos, "A detail of the former Public Library on Hereford Street".