The benefits of urban trees are increasingly becoming more widely understood due to recent well documented projects. Trees provide a variety of ecosystem services including carbon sequestration and storage, removing harmful pollutants from the air, ameliorating localised air temperatures and reducing surface water run-off.
The results of the London i-Tree project published in December last year demonstrated that London’s urban forest provides a monetary benefit to these services of almost £133m. This figure does not even take into account health and well-being benefits of exposure to trees which various studies have shown improve educational performance, reduce stress and depression, increase recovery times of hospital patients and encourage physical activity.
Understanding the nature and extent of its tree stock allows a local authority to make strategic plans regarding its management. A deeper understanding by decision makers of the urban forest as a valuable asset will help to increase tree management budgets.
A well-managed tree stock provides considerable returns and should not be seen as a liability, particularly for highway trees where the largest proportion of tree budgets are typically spent and there is often a disconnect between the cost / benefit ratio of trees.
Urban Green have been working collaboratively with Salford City Council to carry out an audit and risk assessment of over 30,000 highway trees in order to provide a baseline on which to make strategic decisions and formulate a tree policy. Typically, in the absence of detailed survey data, a tree officer often has to deal with all enquiries pertaining to trees with no discernment of whether the enquiry should actually be investigated.
However, Salford City Council has recently adopted a Tree Management Policy which provides ‘a source of information and reference regarding trees on city council land and as a framework for any decisions with regard to the management of trees’.
Since adopting the policy, Paul Jones, the arboricultural client officer has been able to schedule the tree team’s time more effectively and prioritise enquiries to avoid unnecessary and costly callouts.
Like all local authorities, Salford City Council recognises its responsibility as a tree owner to ‘ensure that its trees do not pose a danger to the public or property and are managed appropriately’ including identifying opportunities for establishing new trees in order to replace ageing trees and increase canopy cover.
Urban Green carried out the survey of highway trees using their own bespoke mobile application for data collection to inform a sensible and balanced tree risk management schedule. Using Esri GIS technology, the highway trees were plotted accurately on a satellite imagery base map for ease of identification by the council and its contractors. Each tree on the map can be clicked to reveal relevant data, recommendations, photographs and inspection schedules.
GIS is now such a familiar part of our everyday lives with satnav readily available and Google Earth and Google Maps being used by millions of people on a daily basis on PCs and mobile devices.
Salford City Council now have a detailed inventory of highway trees that they can view and manage using a ‘live’ web mapping application which can be updated as circumstances change. Re-inspections are simple to carry out as all geographic locations and tree data are now logged.
This information can be utilised further to form the basis of an iTree or similar project, which enables a local authority to place a monetary value on their urban forest such as in Greater London whose trees were given an amenity value of over £43bn.
Scott Fitzgerald is director of Urban Green.