Why some UK homeowners reduce the size of their front garden trees and the consequences for urban forest benefits as assessed by i-Tree ECO

The establishment of large-sized trees in the urban environment is an effective means of supplying substantial ecosystem services and benefits to the local community. Privately owned trees often constitute more than half of tree cover in UK cities, yet they are vulnerable to harsh pruning or removal which could substantially reduce or negate the benefits that could be gained from them. In this study, homeowners in Preston, Lancashire were questioned about their management proposals for the young trees planted in the front gardens of four relatively new housing developments. When told the typical mature size of their front garden tree, 79% of these homeowners stated that they would restrict the future size of their tree or remove it, with the level of proposed pruning found to be linked to the distance between the tree and the property. i-Tree ECO was used to quantify the current ecosystem services provided by the trees situated in the front gardens and public open spaces (POSs) of these four developments. Two future projections were also considered: one in which the trees grew unrestricted for the next 10 years and the other in which 87% of the front garden trees were restricted in size or removed to the residents' specifications. Analysis of the i-Tree ECO data showed that the unrestricted trees, in 10 years' time, were likely to annually remove 149% of the pollutants removed by the trees in their current condition. In contrast, the crown-restricted tree population, in 10 years' time, would only be removing 88% of the total pollutants estimated to be removed by the trees in their current condition, a lessening of their pollution amelioration value despite 10 years of growth. This study concludes on the motivations of homeowners in choosing to reduce the size of their trees, the potential loss of benefits to urban forests in the UK due to the attitudes of modern homeowners and on improvements that could be made to i-Tree ECO assessments.