Urban green networks, corridors and linkages

Background

A heathland corridor on Cannock Chase, West Midlands FDGreenspace - also referred to as green infrastructure or green systems - encompasses all types of urban greenspace, ranging from public and private spaces such as domestic gardens, to the open spaces alongside roads and railway lines. The promotion of green infrastructure, or urban greening, has received considerable attention as a means of attracting people into their local natural environment by improving community access, recreation opportunities, and environmental and ecological quality close to and within communities.

Green networks, corridors and linkages are widely seen as a key mechanism for reversing the effects of fragmentation on biodiversity. They also deliver a range of other social and environmental benefits, including enhancement of local landscape character, and greater opportunities for public access and recreational use. Tools to address habitat fragmentation have evolved from principles of landscape ecology, which examines the metapopulation theory, landscape metrics and focal species modelling. There is growing interest in applying these concepts to planning and management of peri-urban and urban areas. The challenge is in integrating these concepts with other, long-established views on the value of greenspaces within urban areas.

Opportunities

There is a focus on identifying and protecting greenspace for people so that they can retreat from the hustle and bustle of urban life, engage in physical activity, improve their health and well-being, and engage in environmental awareness and learning. Through these activities, people will increasingly identify with, and value, the greenspace in their neighbourhood. This can transform environmental quality in urban areas, with a corresponding increase in the economic value of the area, and a stimulation of economic activity and investment.

Land-use planning systems worldwide are now taking into account environmental, social, economic and cultural dimensions. In Britain, recognition of the value of urban greenspace has led to the publication of planning documents setting out guidelines identifying, protecting and encouraging its use, such as the Planning Policy document Planning Policy Guidance 17: Planning for Open space, Sport and Recreation. There is general acceptance that greenspace has a role in both naturalistic (biodiversity-friendly) and formal landscape planning in the UK. This planning guidance highlights the importance of greenspace in promoting social interaction and sustainable planning, and in improving the environment. For example, woodlands can promote biodiversity and help control air and water pollution. Trees, woodlands and other semi-natural environments can also enable the movement of wildlife and people through networks in both urban and rural environments. Greenspace can also help to soften the impact of new developments, making green and civic spaces more appealing.

Current situation

There is now a strong body of evidence to support claims of the multiple economic, social and cultural benefits of urban greenspace. From an economic perspective, urban greenspace is seen as a means to stimulate urban regeneration and improve the quality of social housing. Using techniques such as hedonic pricing and contingent valuation, economists have quantified these benefits in specific locations by correlating the planting of trees or creation of greenspace with increases in property prices and willingness to pay for, or relocate to, greener environments. Such evidence holds much weight with decision-makers, but it is often the less tangible values of greenspace that local people may most readily identify as important in their lives.

A report commissioned by Scottish Natural Heritage (Land Use Consultants, 2004) identifies numerous links with people’s quality of life, including benefits such as community cohesion, empowerment and development. By providing a shared place for social interaction to take place, urban greenspaces can help social networks to develop and increase people’s sense of belonging, cohesion and community. Active participation in projects that aim to increase the quality or functionality of greenspace can enhance these benefits.

There is a drive towards improving the extent and linkage of greenspace within the urban environment, and an aspiration to adopt green networks as a planning strategy, for example the Glasgow Clyde Valley Green Network Partnership. The adoption of a green networks approach to spatially target the provision of greenspace and increase connectivity can offer a more effective strategy over simply increasing the amount of greenspace.

Case study - Improving habitat networks within Core Development Areas

As well as providing habitat for biodiversity, habitat networks can provide valuable recreational opportunities for communities. The region of Edinburgh and the Lothians has a population of 778,000 (2001 census) and a housing requirement growing at a rate of 5000 per year. There is growing recognition of the benefits of woodland in the urban environment, and the need to improve and expand urban woodland close to communities.

The urban and peri-urban areas of Edinburgh and the Lothians contain a range of habitat types, including old woodlands that appear on maps from the 17th century. A study initiated by the unitary authorities, Scottish Natural Heritage and the Forestry Commission has attempted to assess the biodiversity contribution made by woodlands and heathland at the landscape scale, and to evaluate where effort should be targeted to consolidate high-quality habitat, and link existing network components by woodland expansion.

Maps of the distribution of woodlands and other land-cover types were assembled in a GIS. Forest Research used the land-cover data to evaluate habitat linkages across the region’s landscape, using a landscape evaluation tool from the Biological and Environmental Evaluation Tools for Landscape Ecology (BEETLE) toolkit. This tool examines the likelihood of woodland being functionally linked in the landscape and therefore of species being able to move from one woodland patch to another.

As part of the analysis, Forest Research identified networks that contain woodlands of high biodiversity quality, using as indicators the presence of ancient woodland plants from records held by the Lothian Wildlife Information Centre.

For more detail and recommendations see:

Ray, D. and Moseley, D. (undated) A Forest Habitat Network for Edinburgh and the Lothians: The contribution of woodlands to promote sustainable development within the regional Structure Plan (PDF-831K). Forest Research, Roslin, Midlothian.

Urban networks for people and biodiversity

The Urban networks for people and biodiversity project examines and proposes a direction for the implementation of networks in urban environments. This was undertaken through a review of recent approaches for the identification and analysis of habitat networks, with an examination of opportunities to apply these to urban areas.

Through the project, a range of methods for identifying and assessing the value of green networks for people were explored, linking relevant social and environmental data sets to green network data. The approach taken combined an assessment of the biodiversity value of greenspace with a novel use of focal species modelling, to determine how a range of people use greenspace.

The determination of networks for both approaches is based on a GIS-based model (accumulated cost-distance) from the Biological and Environmental Evaluation Tools for Landscape Ecology (BEETLE) toolkit. Greenspace patches were identified for each biodiversity or person class, and the permeability of the intervening matrix was scored for movement or dispersal. The permeability scores were used to calibrate dispersal distances and create buffers of varying distance around greenspace patches. Functional connectivity between greenspace patches occurs where buffers intersect, and greenspace networks are defined as areas of connected greenspace.

The network outputs indicate how greenspace accessibility and use can be combined with the assessment of biodiversity networks to help identify where greenspace may be limited for particular groups in society, and where greenspace of a range of biodiversity values may currently be fragmented. For detailed results see the Urban networks for people and biodiversity project.

This approach expresses the current and potential networks for both people and biodiversity, using a range of user types and biodiversity groups. These indicate how the model networks could be used to target greenspace improvements in order to meet a range of social and environmental policy objectives, such as those relating to physical activity and open space, social inclusion, biodiversity action plans, sustainable urban drainage systems and sustainable transport.

Strategies to improve urban green networks for people and biodiversity will inevitably involve some compromises. This may involve a balancing act to prioritise where areas of higher biodiversity overlap with areas with greater potential for social benefit.

Services

Forest Research has extensive experience of a range of habitat network analyses within woodlands, semi-natural open ground and the urban environment, providing an integrated approach for addressing greenspace enhancement.

Work has been undertaken at national, regional and local scales for government agencies, national parks and unitary authorities. Landscape ecology tools have been combined with social research to develop an approach to enable planning departments to manage greenspace as multifunctional urban green networks.

Ecological, environmental, and social data are considered within national and local policy issues to produce solutions taking into account the complex nature of greenspace provision.

Forest Research tailors outputs to customer requirements. Using our guidance documentation, GIS files can be used with other planning tools to aid development of structure plans and local biodiversity action plans, forming an integral part of greenspace planning to improve urban ecosystem services and public health.

Further information

Communities and Local Government (2002). Planning Policy Guidance 17: Planning for Open space, Sport and Recreation. Communities and Local Government, UK.

Eycott, A., Watts, K., Moseley, D. and Ray, D. (2007). Evaluating Biodiversity in Fragmented Landscapes: the Use of Focal Species (PDF-3460K). Information Note No. 89. Forestry Commission, Scotland.

Forest Research (undated). A Forest Habitat Network for Edinburgh and the Lothians (PDF-831K). Northern Research Station, Forest Research Scotland.

Land Use Consultants (2004). Making the links: greenspace and quality of life. Scottish Natural Heritage Commissioned Report No. 060 (ROAME No. F03AB01).

Lawton, J.H., Brotherton, P.N.M., Brown, V.K., Elphick, C., Fitter, A.H., Forshaw, J., Haddow, R.W., Hilborne, S., Leafe, R.N., Mace, G.M., Southgate, M.P., Sutherland, W.A., Tew, T.E., Varley, J., and Wynne, G.R. (2010). Making Space for Nature: a review of England’s wildlife sites and ecological network. Report to Defra.

Watts, K., Humphrey, J., Griffiths, M., Quine, C. and Ray, D. (2005) Evaluating Biodiversity in Fragmented Landscapes: Principles (PDF-488K). Information Note No. 73. Forestry Commission, Scotland. 

Watts, K., Ray, D., Quine, C., Humphrey, J. and Griffiths, M. (2007) Evaluating Biodiversity in Fragmented Landscapes: Applications of Landscape Ecology Tools (PDF-6440K). Information Note No. 85. Forestry Commission, Scotland.


Glossary

Contingent valuation

The contingent valuation method (CVM) is used to estimate economic values for all kinds of ecosystem and environmental services. It can be used to estimate both use and non use values, and it is the most widely used method for estimating non-use values. It is also the most controversial of the non-market valuation methods.

Focal species modelling

Modelling the habitat requirements and landscape use of a particular species of interest.

Hedonic pricing

The hedonic pricing method is used to estimate economic values for ecosystem or environmental services that directly affect market prices. It is most commonly applied to variations in housing prices that reflect the value of local environmental attributes.

Landscape metrics

Indices that quantify specific spatial characteristics of patches, classes of patches, or entire landscape mosaics.

Metapopulation theory

A metapopulation consists of a group of spatially separated populations of the same species which interact at some level. Although individual populations have finite life-spans, the population as a whole is often stable because immigrants from one population (which may, for example, be experiencing a population boom) are likely to re-colonize habitat which has been left open by the extinction of another population.