Valuing the benefits of urban trees for better greenspace management
By Kathryn Hand, Kieron Doick, Liz O’Brien, and Clare Hall from Forest Research, and Susanne Raum from Imperial College London
Urban trees as greenspace and their benefits
When we think of greenspace, we usually think of parcels of green land: parks, sports fields, maybe gardens. While trees are important features within these landscapes, they can also be seen as small patches of greenspace in their own right – offering an area of green in an otherwise grey urban realm and ranging from single trees in gardens, parks and streets, to small clusters of trees and those that make up urban woodlands. Together all of the trees across an entire urban area are known as the ‘urban forest’1.
Urban forests can provide many benefits, also known as ‘ecosystem services’, to society2. These benefits help make our towns and cities healthier, more sustainable and liveable. Urban trees can contribute to public health by removing harmful pollutants from the air, encouraging active lifestyles and helping to reduce the stress of those who live near them. Tree canopies help to provide shade to cool urban areas, and also intercept rainfall to reduce runoff, thereby reducing the risks from flooding. Finally, trees make places special – they can provide a link to local history, support local nature, and create a source of cultural and spiritual value.
Valuing the benefits of urban trees using i-Tree Eco
While people value and appreciate trees for many reasons, often the benefits they provide are not considered when decisions that govern their future are being made. When the benefits of trees go unvalued, their maintenance costs can appear to be an unjustifiable expense. In recent years, tree officers have seen their budgets shrink3. These changes are also common to other areas of greenspace such as parks4. In an attempt to address these trends, urban authorities have begun to assess and value their urban forest resources to account for the benefits that trees provide society. By putting a £-value on urban trees it is hoped their benefits can be formally recognised and their management improved, to the benefit of both the urban forest and those who live, work and visit urban areas.
i-Tree Eco (www.itreetools.org) is a tool that provides information on the state of the urban forest, including the species composition, age structure and condition. It then calculates the quantity and value of the benefits provided by those urban trees for four ecosystem services: carbon storage, carbon sequestration, avoided stormwater runoff, and removal of air pollution.
i-Tree Eco was first used in the UK in 2011; Torbay’s urban forest was estimated to provide a total annual benefit of over £345,0005. Since then, i-Tree Eco has been used in over 20 UK projects, ranging from assessment of a small park to whole cities, such as Edinburgh (figure 1).
Evaluating the impact of i-Tree Eco in the UK
With the use of i-Tree Eco growing in the UK, an evaluation study was conducted by Forest Research to review the impact that these projects have had on the management of urban forests, and to evaluate the role of i-Tree Eco in protecting and expanding the urban forest.
The study found that the impact delivered by i-Tree Eco projects varied. The results from some projects had fed into changes in policy and local funding, while others have had less impact so far. In most of the i-Tree Eco projects there had been improvements in understanding the benefits of urban trees, and greater connectivity and collaboration between local authority departments. Overall, the evaluation study found that i-Tree Eco had two key roles in protecting and expanding the urban forest:
1. Providing the evidence base to inform management decisions: Key information on the health and composition of urban forests can help tree officers and policy-makers to better understand the state of the urban forest and its benefits. Often the i-Tree Eco assessments helped to identify emerging vulnerabilities in the urban forest, such as an aging tree population, or over-reliance on a limited number of tree species. For example, a predominance of ash trees, which is a concern given the threat from chalara ash dieback. Having detailed information from i-Tree Eco on the current state of the urban forest and its vulnerabilities provided the opportunity to inform the development of detailed urban forestry management plans and a strategy for the long-term continuation of its benefits.
2. Putting a £-value on benefits to make them explicit and help raise awareness: While many people may be able to recognise the benefits of trees, calculating how much these benefits are worth can help others to understand and appreciate this benefit. This can help to balance the argument against the costs of tree maintenance and provide a rationale for investment in the urban forest. One of the evaluated projects was able to use their i-Tree Eco results to help secure an additional tree officer, while another received an increase to its tree maintenance budget. In many other cases, the values produced by the i-Tree Eco projects - often millions of pounds - helped to improve awareness of the importance of urban trees and counter negative perceptions of trees. Further, understanding how trees contributed to different benefits, for example mitigating the effects of a changing climate, enhanced conversations between council departments and led to the inclusion of urban trees in broader policies, such as local development plans and green infrastructure strategies.
Lessons learned for valuing urban greenspace
In summary, valuing trees using tools such as i-Tree Eco, can be useful in providing the evidence to support our urban trees, as well as motivating change and investment. The impact of i-Tree Eco did vary between the projects that were evaluated. On the other hand, opportunities to overcome barriers that limited the impact of the valuation projects were also identified (see the full evaluation report for further details: https://c-js.co.uk/2wbEq2g). Hopefully many more UK towns and cities will follow this lead and evaluate their urban forest using i-Tree Eco, or a similar tool (to learn more visit:
For more information, contact: Kieron Doick at Forest Research (https://www.forestresearch.gov.uk/staff/kieron-doick/)
1 Urban Forestry and Woodlands Advisory Committee Network (UFAWCN). (2017). Introducing England’s urban forests. Urban Forestry and Woodlands Advisory Committee Network. Available online at: https://c-js.co.uk/30AI835
2 Davies, H.J., Doick, K.J., Handley, P., O’Brien, L., Wilson, J. (2017). Delivery of Ecosystem Services by Urban Forests. Forestry Commission Research Report 26. Forestry Commission, Edinburgh, 34 pp.
3 London Tree Officer Association (LTOA). (2016). Tree management in London boroughs. London Tree Officer Association. London, UK.
4 Heritage Lottery Fund. (2016). State of UK public parks 2016. Heritage Lottery Fund, 124 pp.
5 Rogers, K., Jarratt, T. and Hansford. D. (2011). Torbay’s Urban Forest. Assessing urban forest effects and values. A report on the findings from the UK i-Tree Eco pilot project. Treeconomics, Exeter. 46 pp.
6 Doick, K.J., Handley, P., Ashwood, F., Vaz Monteiro, M., Frediani, K. and Rogers, K. (2017). Valuing Edinburgh’s Urban Trees. An update to the 2011 i-Tree Eco survey – a report of Edinburgh City Council and Forestry Commission Scotland. Forest Research, Farnham. 86 pp.