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Images, eqnz.chch.2010

Messages strung on rope by the Peace Bell at the Christchurch Botanic Gardens in commemoration of the anniversary of the 22 February 2011 earthquake. File reference: CCL-2014-02-22-22February2014 DSC_1218.JPG Photo taken by Valerie Livingstone. From the collection of Christchurch City Libraries.

Research Papers, Lincoln University

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.

Images, UC QuakeStudies

An aerial photograph looking west over the Arts Centre and Christ's College towards Hagley Park. The photograph has been captioned by BeckerFraserPhotos, "At the centre of this photo is a group of heritage stone buildings. Canterbury Museum and Christ's College were extensively earthquake strengthened prior to the EQs and re-opened to the public relatively quickly. The Arts Centre is undergoing extensive renovations. Hagley Park and the Botanic Gardens provide a richly colourful surrounding to these historic buildings".