Vegetation in towns and cities can make a significant contribution to carbon storage and, ecologists say, could lock away even more carbon if local authorities and gardeners planted and maintained more trees. The study, published this week in the British Ecological Society's Journal of Applied Ecology, is the first to quantify how much carbon is stored in vegetation within an urban area of Europe.
Using satellite data and information gathered by visiting local parks and gardens, the researchers surveyed vegetation across Leicester, including domestic gardens and council-owned parks, golf courses, abandoned industrial land, road verges and river banks.
They found 231,000 tonnes of carbon (C) locked up in Leicester's above-ground vegetation, equivalent to 3.16 kg C per square metre of the city, an order of magnitude greater than current national estimates. Most of this carbon pool is associated with trees.
According to lead author Dr Zoe Davies of the University of Kent: "Large trees are especially important carbon stores. Most of the publicly owned or managed land across Leicester is grassland. If just 10% of this were planted with trees, the existing carbon pool across the city could be increased by 12%."
"Trees, particularly large ones, should be protected and maintained and if more trees are planted in urban areas for their carbon storage value, they must be the right kind of tree planted in the right place so that they have a long, productive life span, and when trees die they should be replaced," she says.
The data - which until now were lacking - are particularly important because local government will play a key part in helping the UK government meet its target of an 80% reduction in greenhouse gas emissions, from 1990 levels, by 2050.
According to Dr Davies: "Currently, once land in the UK is considered to be urban its biological carbon density is assumed to be zero. Our study illustrates this is not the case and that there is a substantial pool of carbon locked away in the vegetation within a city - another reason why urban trees and greenspaces should be valued."
"Although it is not a panacea for emissions reduction, our results demonstrate the potential benefits of accounting for, mapping and appropriately managing above-ground vegetation carbon stores, even within a typical densely urbanised European city," Dr Davies says.
The study is an output from "4M: An Evidence Based Methodology for Understanding and Shrinking the Urban Carbon Footprint", a £2.5m EPSRC-funded project by Loughborough University, De Montfort University, Newcastle University, University of Sheffield and the University of Exeter.
Zoe G Davies et al (2011), 'Mapping an urban ecosystem service: quantifying above-ground carbon storage at a city-wide scale', doi: 10.1111/j.1365-2664.2011.02021.x, is published in the Journal of Applied Ecology on 12 July 2011.