Bicester and beyond
Alison Smith on creating a green infrastructure toolkit to help local authorities and policy makers deliver long-term results
The town of Bicester in Oxfordshire will almost double in size in the next 15 years, with 10,000 new homes bringing the population from 30,000 to over 50,000. The government’s Local Plan states that this growth should be sustainable, and this goal is backed up by the designation of Bicester as both a Garden Town and a Healthy New Town.
The aims are to build low-energy homes, provide opportunities for walking and cycling, and protect local biodiversity. An important part of this vision is green infrastructure, which presents both challenges and opportunities.
The local authority, Cherwell District Council, wants to make new and existing green space more multifunctional and more connected – for both wildlife and people – to make the most cost-effective use of the space available. However, in common with many other planning authorities, it lacks access to suitable tools for assessing the plans provided by developers, to check whether the green infrastructure has been optimised to meet the needs of local people and maintain or improve biodiversity.
So the council approached our group at the Environmental Change Institute (part of the University of Oxford) and, together with other project partners, we obtained funding from the NERC Green Infrastructure Innovation scheme to develop a toolkit that could be applied both in Bicester and by other local authorities.
Priority ecosystem services for Bicester were identified at an initial scoping workshop for all the project partners, including the town, district and county councils, local wildlife groups, the Environment Agency and developers. Priorities were recreation, water quality regulation, flood protection, urban food production, wildlife habitat, sense of place and aesthetic value, with air quality, local climate regulation, water supply and pollination also being important. The challenge was to find tools that could address this wide range of services.
Numerous tools are emerging to map and assess ecosystem services, and websites such as the OPPLA hub and Natural Capital Protocol Toolkit offer useful guidance. The Ecosystems Knowledge Network has profiled 12 of the analytical tools that are most ready for application in the UK, ranging from simple spreadsheets to models that require advanced GIS software. Only a few of these are suitable for use by local authority planners with limited time, budget and resources. However, we did find some quick and simple approaches, based on land-use scoring, that seem promising for an initial assessment.
In these methods, different land-use types are assigned a score such as from 1 to 5, depending on how well they provide different ecosystem services such as flood protection or recreation. The scores, which are typically derived from a survey of local experts backed up with a literature review, can then be used to produce illustrative maps of ecosystem service supply. Although this is purely an exploratory approach, it can help planners and other stakeholders to quickly visualise which areas are valuable for providing key services, and identify gaps where supply is lacking and new green infrastructure could be created.
In Bicester, which is surrounded by intensively farmed land, these maps revealed the key role of the remaining areas of semi-natural grassland in providing regulating services and wildlife habitat. Flood protection is in particularly short supply, with little woodland in the catchment upstream of the town. There is also little vegetation for air-quality regulation in the town centre and around the busy ring-road.
The approach can be taken a step further with tools such as the Natural Capital Planning Tool, being developed at the University of Birmingham and due to be released in spring 2018. This is simply a spreadsheet that multiplies land-use scores by the surface area of each land-cover type to produce a single score for an entire development site. By scoring the site before and after development, the user can estimate whether the site has achieved a net loss or gain for ecosystem services, building on the concept of No Net Loss for biodiversity. The Natural Capital Standard for Green Infrastructure, being developed by the Scottish Wildlife Trust, takes a similar approach, producing a Green Infrastructure score for a development site which can be compared to an ‘acceptable’ threshold score, or used to compare alternative development options.
These tools are intended to be used at the planning stage, to ensure sites are optimised to deliver good-quality green infrastructure. It is possible to apply weights to the different services to reflect local priorities, and to adjust the scores for certain land parcels – for example, to give a higher score to exceptionally good-quality infrastructure. However, although it is reasonably easy to compile a set of scores that reflect the ranking of different land-use types, the scores do not necessarily reflect the absolute magnitude of the service accurately. For example, forests might score 5 for flood protection and amenity grassland might score 1, but this does not necessarily mean that forests reduce run-off by five times more than grassland. The output should therefore be interpreted cautiously.
We are also investigating tools for estimating the value of green infrastructure. These include iTree-Eco for valuing the benefits of urban trees (working with Forest Research), and free spreadsheet tools such as the Green Infrastructure Valuation Toolkit and the BEST SuDS tool. These tools provide useful frameworks for evaluation, but are constrained by the availability of reliable data on costs and benefits.
Although it is possible to put a monetary value on some of the benefits of green infrastructure, such as the health benefits of reduced air pollution, some of the less tangible cultural benefits are best valued in different ways. We are using a variety of participatory approaches to systematically assess the value that local people attach to their green spaces, including street surveys, a drop-in consultation, an on-line app and a workshop. We focused on six cultural ecosystem services, including recreation, aesthetic value, education, local identity (‘sense of place’), wildlife habitat and existence value (the benefit of just knowing that a place exists). The responses show the high value that local people place on their green spaces, and the benefits that they receive – not just from the large parks and nature reserves, but also from small local green spaces and street trees.
Need for networks
Our project is still in progress, but some initial messages are emerging. Connectivity of green infrastructure is a problem, both for people and wildlife. Habitat mapping shows that semi-natural habitats are fragmented and isolated, and the public consultation also highlighted a lack of connected routes for cyclists and walkers. These findings present an opportunity to build in better networks across and around the town as part of new developments. There are also opportunities to use strategic planting to help protect against air pollution at certain sites in the town centre, but we found a lack of guidance for local authorities on what species of trees and plants are best for air-quality improvement. We aim to provide better guidance on this as part of our project outputs.
Looking at the wider messages from our project, land-use scoring provides a quick, first-cut approach for mapping and assessing green infrastructure and ecosystem services. Public participatory approaches complement land-use scoring maps by adding local detail such as identifying sites that should be scored lower or higher, setting local priorities and providing suggestions for improvements, as well as improving the transparency and legitimacy of the process.
Finally, there is no point designing high-quality green space if the long-term governance and maintenance is not secured. Local plans need to find ways of building in strong protection for the future use, maintenance and governance of both public and private green space, so that it continues to deliver benefits into the long term. We hope to deliver a toolkit that will enable them to generate the evidence to support this.
Alison Smith is a research scientist at the Environmental Change Institute, University of Oxford