The urban environment has distinctive biophysical features in relation to surrounding rural areas. These include an altered energy exchange creating an urban heat island, and changes to hydrology such as increased surface runoff of rainwater. Such changes are, in part, a result  of the altered surface cover of the urban area. For example less vegetated surfaces lead to a decrease in evaporative cooling, whilst an increase in surface sealing results in increased surface runoff. Climate change will amplify these distinctive features. This paper explores the important role that the green infrastructure, i.e. the greenspace network, of a city can play in adapting for climate change. It uses the conurbation of Greater Manchester as a case study site. The paper presents output from energy exchange and hydrological models showing surface temperature and surface runoff in relation to the green infrastructure under current and future climate scenarios. The implications for an adaptation strategy to climate change in the urban environment are discussed. 

This research was funded by the Engineering and Physical Sciences Research Council and the UK Climate Impacts Programme. Information about the Adaptation Strategies for Climate Change in the Urban Environment (ASCCUE) project, which includes the work presented here, can be accessed via the CURE pages within the School of Environment section of the University of Manchester website. 

The article was published in the journal Built Environment; Vol 33, no. 1.

The research fi ndings presented here are significant because they begin to quantify the potential of the green infrastructure to moderate climate change impacts in towns and cities. Such claims are often made for urban greenspace (e.g. Hough, 2004) but the introduction of a modelling approach clarifies the magnitude of the effect and allows adaptation strategies to be tested. We do not suggest that the model outputs can be directly translated in practice, for example it would be quite unrealistic to green all roofs in city centres and high-density residential areas. However, the model runs indicate which type of actions are likely to be most benefi cial and in which locations. Urban greenspace from street trees, to private gardens, to city parks provide vital ecosystem services which will become even more critical under climate change.

Within urban centres green spaces therefore constitute critical  environmental capital that, once developed, is difficult to replace. This green-space needs to be strategically planned. The priorities for planners and greenspace managers is to ensure that the functionality of greenspace is properly understood and that what exists is conserved. Then it shouldbe possible to enrich the green cover in critical locations,  for example the planting of shade trees in city centres, schools and hospitals. Opportunities to enhance the green cover should also be taken where structural change is taking place, for example, in urban regeneration projects and new development. The combination of the  UMT-based modelling approach with the patch-corridor-matrix model may help in the development of spatial strategies for the green infrastructure to preserve existing greenspace and create new greenspace such that a functional network is formed. This approach, however, requires further exploration.

Mature trees will be very important for the roles they play in providing shade and intercepting rainfall. Also, in times of drought they may  provide a cooling function for longer than grass, which will dry out faster. At present, those areas experiencing highest surface temperatures and socio-economic disadvantage also have the lowest tree population and here urban forestry initiatives, such as the Green Streets project of the Red Rose Forest of Greater Manchester, are beginning to redress the balance. During periods of water shortages, as for example has happend in South East England, urban vegetation is often the first target of a  drought order’. The research suggests that the benefits of greenspace go well beyond consideration of amenity and that opportunities will have to be taken to ensure an adequate water supply to vegetation in times of drought.

Climate change is already with us and there is an urgent need to develop adaptive strategies. The creative use of the green infrastructure is one of the most promising opportunities for adaptation and this needs to be recognized in the planning process at all scales from the Regional Spatial Strategies, through Local Development Frameworks to development control within urban neighbourhoods. Within the government’s  sustainable Communities Programme there is real scope to ‘climate proof’ new developments in the Growth Areas and to reintroduce functional green infrastructure during the redevelopment process in areas subject to Housing Market Renewal.

//2007

S.E. Gill, J.F. Handley, A.R. Ennos, and S. Pauleit

research

Urban Policy > Urban environment

Environmental sustainability