As populations become increasingly urbanised, national governments to local councils are recognising that the trees that line our streets, fill our parks and shade our houses make up an urban forest. Urban forests provide multiple benefits that go far beyond adding aesthetic beauty to our neighbourhoods. Trees in parks, streets and yards, conserve energy, reduce carbon dioxide in the atmosphere, improve air quality, reduce storm runoff, and enhance the beauty of our communities by adding colour, texture, and form to our landscapes.
In addition, no matter where trees are located, they represent an interdependent part of complex ecosystems capable of providing a wide range of economic, social and environmental benefits. All these benefits should be considered when attempting to measure the economic, social and environmental benefits of our street trees. These benefits and services, however, are valued differently by different people and different groups in society. Local, regional, national and international interests in our urban trees and the resources they provide also differ greatly and tend to shift over time.
As interests shift and expectations conflict, difficult policy and management challenges are created, requiring innovative national, regional and local strategies that better integrate urban trees into community development efforts and balance economic, social and environmental needs among local, national, and even international interests. The emerging views of what urban trees are and what they contribute require local governments to search for pragmatic management strategies that deal coherently with both the contributions of trees to urban development and to search for organisational structures to make better use of these contributions.
The roles of urban forestry in general, and street trees in particular (ie., the knowledge, concepts, institutions and practices through which multiple and competing demands for trees are managed), are changing as well. The changes are emerging as awareness grows of how local communities control and depend on trees and urban forests, prompting efforts to strengthen local stakes in urban forestry and street tree management, programs and activities.
Developing effective forestry strategies and policies involves an array of difficult choices. Some choices result in inefficient resource use because many essential benefits and services of street trees, such as aesthetic values, watershed protection, conservation, biological diversity and climate regulation are not priced. Markets with corresponding prices just do not exist for many important street tree services and benefits. The result is that street tree decisions are often biased because the information is lacking.
An important message of this paper is that it is very difficult to address the total economic, social and environmental benefits of street trees because of the multiple roles and competing interests. To some, street trees represent a nuisance, dropping their fruit, branches, and leaves, raising sidewalks or shading their ‘heritage’ roses.
To others, street trees are a noise barrier and an air filter, adding value to their neighbourhood and their properties.