A Review of Urban Forest Benefits and Costs

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morgenroth, justin

Effective urban forest management requires an understanding of tree costs and benefits. Costs can include producing or acquiring trees, site preparation (often including infrastructure requirements), planting, irrigation, inspections and pruning, traffic management, integrated pest management, leaf litter removal, storm cleanup, infrastructure damage, removal, and administration. Benefits, also called ecosystem services, are typically categorised as provisioning, cultural, supporting, or regulating services. The objectives of this report are to provide insight into the economic costs and benefits of urban trees. These objectives were met by thoroughly reviewing existing scientific and grey literature, summarising the reported data, and interpreting the findings. On balance, the benefits of urban trees were found to outweigh the costs. For studies with roughly comparable methods, annual tree benefits ranged from $110.16–$490.06, while annual costs, per tree, generally ranged between roughly $68–$99. Excluding outliers, the studies that reported both costs and benefits of urban trees showed that the benefit-to-cost ratio (BCR) of urban trees ranged between 1.35 and 6.69, with an average of 3.39. This means that for every $1 invested on trees, trees returned $3.39 worth of benefits. Tree size and lifespan, both related to species, had an influence on tree BCR. Generally speaking, the larger a tree and the longer it lives, the greater the tree’s benefit-to-cost ratio. Modelled values show that, on average, large trees (BCR = 3.93) have a BCR 2.8 times greater than small trees (BCR = 1.4). Costs were known with greater certainty than estimates of the economic value of benefits. Costs are relatively accurately quantified in budgets. In contrast, many benefits remain unquantified or under-quantified with most studies focusing on a small number of benefits. This under-quantification of urban forest benefits suggests that the BCRs reported in many studies are conservative and that the benefits of investments in urban trees are likely greater than the average BCR of 3.39 presented in this report. No New Zealand-based studies exist from which to draw knowledge. To gain a local accurate estimate of urban tree benefits and costs, Auckland Council should consider undertaking its own assessment using the newly available i-Tree NZ. This proposed local study would give Auckland Council greater certainty over the benefits and costs associated with the urban trees they manage, rather than having to rely on overseas studies.

Morgenroth J (2023). A Review of Urban Forest Benefits and Costs. Auckland Council.
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
30 - Agricultural, veterinary and food sciences::3007 - Forestry sciences::300707 - Forestry management and environment
33 - Built environment and design::3304 - Urban and regional planning::330404 - Land use and environmental planning
33 - Built environment and design::3304 - Urban and regional planning::330410 - Urban analysis and development
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