Redeveloping the urban forest: The effect of redevelopment and property-scale variables on tree removal and retention

Abstract

The effects of urbanization on urban forest canopy cover has received significant consideration at broad scales, but little research has explored redevelopment-related influences on individual tree removal at a property scale. This study explores the effect of residential property redevelopment on individual trees in Christchurch, New Zealand. The study monitored 6966 trees on 450 residential properties between 2011 and 2015/16. Of the 450 properties, 321 underwent complete redevelopment during that time, while 129 were not redeveloped. The percentage of trees removed on redeveloped and non-redeveloped properties differed markedly, being 44% and 13.5%, respectively. A classification tree (CT) analysis was used to examine the effects of different combinations of 27 explanatory variables, describing land cover, spatial relationships, economic, and resident and household variables, on tree removal or retention on the properties. The best model included land cover, spatial, and economic variables (accuracy = 73.4%). The CT of the corresponding model shows that trees were most likely to be removed if they were within 1.4 m of a redeveloped building on a property with a capital value less than $1,060,000 NZ. The strongest predictor of tree retention was that the property was not redeveloped. The model predicted that trees were over three times as likely to be removed from a redeveloped property relative to a property that was not redeveloped. None of the seven resident and household variables were selected by the CT as important explanatory variables for tree removal or retention. These results provide insights into the factors that influence tree removal during redevelopment on residential properties, and highlight the need for effective tree protection during redevelopment.