iTree & the Benefits of Trees

iTree Bristol

Data recorded in the volunteer surveys in summer 2018, has now been processed through the iTree Eco 6 model. Results show that each year trees in Bristol provide environmental services worth around £2.7 million, removing about 100 tonnes of air pollution, reducing flood risk by soaking up some 90,000m³ of water and removing 14,000 tonnes of carbon dioxide, equivalent to the annual emission of about 9,000 cars. They also deliver many other services benefiting our quality life: download summaries of the results in the panel below.

iTree Bristol is supported by the Forest of Avon Trust, Bristol City Council, the Woodland Trust, Forestry Commission SW and Bristol Tree Forum. 

Action Plan for Bristol's Urban Forest

Bristol’s canopy cover is currently around 12%, but experts believe that the figure needs to increase this substantially to help us combat climate change and air pollution, protect biodiversity and promote health and wellbeing. Bristol’s One City Plan, published in January 2019, is calling for tree canopy cover to be doubled by 2046. 

The Forest of Avon Trust is working with Bristol City Council, the Woodland Trust and the Bristol Tree Forum to produce an Action Plan to set out how this tree (and management) can be funded and delivered (on public and private land) in to the future. 

Critical to this process is the involvement of people across the city: the One City Plan whilst rightly ambitious, could be achieved if everyone in Bristol planted just three trees! 

iTree Bristol Background

iTree Eco 6 Context

iTree Eco has been widely and successfully used in the USA and is a robust valuation model for the range of environmental services provided by trees. In Britain, it was first used in Torbay in 2011, with its application quickly widening and informing tree care budgets and investment decisions in 16 cities including Edinburgh, Glasgow, London and Manchester. The latest version (iTree Eco 6) generates an even wider range of data on the environmental services provided by an area’s trees.

iTree Bristol Context

iTree Bristol was delivered by the Forest of Avon Trust, who helped fund it along with partners Bristol City Council, the Woodland Trust, and the Forestry Commission.  An important part of the brief for the work was that the survey should be undertaken by volunteers and along with Talking Trees: Bristol (run through summer 2018), it should help raise awareness of trees across the city, building interest in Bristol's trees and underpinning the forthcoming Action Plan for Bristol’s Urban Forest (Tree Strategy).  

iTree Bristol Survey  

Using the latest iTree Eco 6 model, the survey ran between May and September 2018. 29 volunteers took part, recruited by the Forest of Avon Trust and through the Talking Trees: Bristol campaign. A total of 201 randomly generated 0.04ha plots were surveyed across the administrative area of the city in this period, the majority being undertaken by volunteers, supplemented by Anna Brunton (Forest of Avon Trust).  

iTree Bristol Report

The documents which can downloaded above summarise the main findings of iTree Bristol report, adapted to make use of the latest UK data.

The full report can be provided on request. 

Please note that whilst iTree Eco 6 has been adopted by at least 16 cities in the UK and makes extensive use of UK data, it is a U.S. model and as such our promoted findings differ in the following ways from the full report. We:

1. Use the latest (2018) UK values adopted by HM Government for avoided run-off, carbon dioxide storage & capture, and pollution capture, which have been by calculated by consultants Treeconomics, using iTree Bristol base data. This is line with best practice for other recent UK iTree studies.
2. Use the most recent (2018) average annual UK car emissions and mileage to calculate comparator values for carbon dioxide storage and capture by Bristol’s trees. The age profile of vehicles in Bristol is not known and emissions may be higher.  
3. Use the avoided run-off figures for trees only, so the figure is lower than in the report. This is to maintain comparability with other findings. Precipitation data comes from the UK climate station closest to Bristol (within iTree Eco 6); the model has also been run with alternative UK precipitation data to check the validity of findings. We aim to run iTree Bristol with a new dataset for Bristol in 2019, although avoided run-off is unlikely to be significantly different.   

To request a pdf of the full iTree Bristol report and/ or to ask any questions about the study, please email: Jon Clark

iTree North Somerset

In 2013 we ran the first UK iTree study to use volunteers for data collection, on behalf of North Somerset Council. The Council re-ran the data  using the iTree Eco 6 model in 2018. For further details email: Jon Clark