Valuing the Natural Capital of Area 1: A Pilot Study

In the summer of 2014, a study was commissioned on behalf of the Highways Agency to provide detailed information on the scale of benefits provided by the natural capital of the ‘soft’ estate in Area 1, expressing the economic value of those benefits in monetary terms.

The Highways Agency own 972 ha of verges, grasslands, shrubs and trees throughout Area 1, which constitutes its ‘soft estate’. This is in addition to its hard or grey infrastructure of carriageways, access road, and bridges. This report represents the first time to date that a highways network has evaluated its soft estate in this way within the UK.

Treeconomics, in collaboration with Kier, Evans and Associates, Forest Research and Davey used existing data, new field work and the i-Tree Eco model to quantify the structure of Area 1’s trees. Data from 72 randomly selected field plots located across the network were analysed.

Poor air quality is a common problem in many urban areas and along many busy road networks. With the increase in population and industrialisation, and the growing use of transport based on fossil fuels, damaging quantities of pollutants are being produced every day.

This analysis determined that the trees of Area 1 removed as much as 29 tonnes of pollutants each year, a service valued at £611,000 per annum. They were estimated to remove an amount of particulate matter (PM10s) equivalent to the annual emissions from 31,000 large family cars.

Area 1’s trees and shrubs were also revealed to store a massive 22,200 tonnes of carbon, a service valued at an astronomical £1,260,000. This is an indication of the amount of carbon that could be released back into the atmosphere if the trees were to be lost.

As a result of the data generated by this project, future projects within the Area 1 network can be both identified and prioritised, accounting for localised benefits to nearby residents and passing motorists. Typical projects are likely to focus on management of existing vegetation in or adjoining residential areas, to guide the vegetation composition and structure in order to maximize benefits, including increased oxygen production and associated pollution removal. Due to the extent of nearby populations adjoining the network, locations for such an approach are likely to include Plymouth, Exeter, Liskeard and Okehampton.

With an amenity asset value determined at an astonishing £40.16 million, the range of benefits from trees within Area 1 are diverse, and when valued in financial terms significantly outweigh the annual cost of maintenance.