The potential role of natural colonisation as a design tool for urban forestry — a pilot study

Traditionally, the establishment of urban trees and forests has involved some element of deliberate design, which includes, at the very least, selection of location and species, followed by planting and subsequent maintenance. However, the ecological stresses of the urban environment can often cause such an approach to end in failure. In contrast, natural colonisation will select only those plants that are adapted to survive in the urban environment. This paper reports on a pilot study of some naturally colonised urban sites in Leeds and examines the potential contribution such processes can make to the urban landscape. Dominant woody species are identified and discussed in relation to their provision of amenity, support of biodiversity, modification of urban microclimate and amelioration of air pollution to help establish the benefits and disadvantages of naturally established woody vegetation as part of an overall urban forestry strategy.