Lifetime cost models for large, long-lived, street trees in Australia

Abstract

ABSTRACT The costs of maintaining an urban street tree over its lifecycle have been considered in cost models. One used in Australia is a typical relationship between the cost and functional and aesthetic benefits of the urban shrub mass. But are these curves typical of larger, long-lived urban street trees growing under Australian conditions? The costs of maintaining an urban street tree under Australian management regimes, including purchase and planting costs of a common street tree species, herbicide and mulching costs, the cost of irrigation over the first summer after spring planting and of formatively pruning the young tree were calculated based on data obtained from Australian local government agencies. The research-modelled management of an urban tree under five scenarios based upon planting a 2–3 m tall tree with a safe useful life expectancy of 50 years. Scenarios included annual maintenance, regular pruning on a 5-year cycle after 15 years and a major arboricultural intervention in the final decade. The impact of longer lifespans of 100 or 150 years was also modelled. The curves demonstrated that costs associated with a street tree are high in the first 2–3 years of its life but much higher in the final year of life leading to removal but differed in shape from other models. The lifetime costs of maintaining a street tree depending on the management scenario are between AUD$2800 and AUD$6220 or AUD$56 and AUD$124.40 per annum. Doubling the lifespan of a street tree reduces the annual management cost by 30%.