Green infrastructure is defined by the European Commission as “a strategically planned network of high-quality natural and semi-natural areas with other environmental features, which is designed and managed to deliver a wide range of ecosystems services and protect biodiversity”;² and by England’s National Planning Policy Framework (NPPF) as “a network of multi-functional green space, urban and rural, which is capable of delivering a wide range of environmental and quality-of-life benefits for local communities”.³ Definitions from Natural England and the Town and Country Planning Association (TCPA) both emphasise that green infrastructure is a multi-functional network, operating at a range of spatial scales.^4,5

Health and wellbeing benefits
Green infrastructure has many benefits for health and wellbeing, and people are likely to be familiar with the evidence that spending time in green space can promote mental wellbeing among individuals, as well as encouraging higher levels of physical activity, promoting community cohesion and reducing social isolation.⁶ But green infrastructure also has a more strategic role to play in supporting the population’s long-term health and wellbeing, through mitigating the adverse impacts of air pollution, noise, heat, flooding and climate change, as well as helping people gain a greater appreciation of the importance of nature and the need to protect it for future generations.^7,8,9,10

Unfortunately, despite evidence that exposure to natural environments has the potential to benefit those in lower socioeconomic groups to a greater extent than those in more affluent groups, people living in the most deprived areas are less likely to live near green spaces and are therefore less likely to experience the associated health benefits.^11,12 They’re also less likely to have access to good quality green infrastructure, and it’s important to remember that not all green environments will automatically be beneficial to health, with poorly maintained environments having the potential to attract anti-social behaviour and crime, resulting in negative impacts on health.

Biodiverse natural environments and those that are clean, well-maintained and in which people feel safe, as well as those that are available in greater proximity and quantity, are associated with greater health and wellbeing.¹³ In the interest of improving health equity, it’s important not only to think about what can be done to ensure new developments are ‘green’ but also how green infrastructure can be retrofitted into existing un-green areas. More importantly, consideration should be given to how any infrastructure that is introduced will be maintained to a high quality over the long term. 

As with all public health interventions, there are several potential barriers to the roll-out of good-quality green infrastructure – for example, cost and resourcing; lack of knowledge about investment priorities; and challenges in evaluating local impacts.

Making the economic case
A recent review of the evidence base by the University of Exeter, on behalf of the Department for Environment, Food and Rural Affairs (Defra), provides information on some of the national-level economic benefits of green infrastructure. Evidence shows that £2.1 billion would be saved annually through averted health costs if everyone in England had better access to green space. The review also highlights that a view of green space from home is estimated to have a health value of £135-452 per person per year, while having your own garden is valued at £171-575 per person per year.¹⁴

It’s also important to make the case for investment directly to developers, as both the Landscape Institute and the Design Council have done by providing case studies of developments that have successfully embedded green infrastructure and public space. These examples have demonstrated how the provision of quality green spaces can have a significant positive impact on land and property prices, attracting investment and acting as a catalyst for wider regeneration.^15,16 The TCPA, however, emphasises that while well-maintained green infrastructure usually becomes increasingly valuable as time goes by, failure to maintain it well can see it become a liability instead of an asset.¹⁷ It’s therefore vital that the case is made for investment in both the installation and maintenance of green infrastructure. Trade-offs may need to be made between installing low-cost infrastructure that will be costly to maintain versus installing infrastructure with higher capital costs but lower long-term maintenance costs.

Guidance on creating and maintaining infrastructure
While a range of resources exist on principles and mechanisms for delivery, as well as case studies of what successful green infrastructure could look like,^18,19,20,21 there is currently a lack of comprehensive guidance on what high-quality green infrastructure should look like, although recent WHO guidance provides some high-level principles.²² In addition to guidance on what makes good green infrastructure, it’s equally important to have clear guidance on what to avoid. Recent guidance from the National Institute for Health and Care Excellence (NICE) on air pollution emphasises that landscape features, such as trees and vegetation in open spaces or ‘green’ walls or roofs, should only be included where they don’t restrict ventilation, and that street trees and vegetation should be managed (for example, by choice of species, siting and pruning), to reduce the risk of restricting ventilation, which could, contrary to the initial intention, result in an increase in localised air pollution by preventing pollution dispersal.²³ The Woodland Trust provides guidance on the installation and maintenance of trees in residential developments.²⁴

Natural England previously developed standard guidance on access to the natural environment, in the form of the Accessible Natural Greenspace Standard; this guidance, however, has now been archived.²⁵ Natural England also supported the development of a number of standards relating to specific types of green space – for example, visitor service standards for national nature reserves, country parks and local nature reserves, as well as the Green Flag Award for parks and open spaces.²⁶ Several local accreditation schemes are now being piloted, including the Building with Nature Award in the South West of England²⁷ and the Green Space Factor and Green Points system in London.²⁸

Evaluating the impacts of green infrastructure
In the absence of clear guidance on what ‘good’ green infrastructure looks like, monitoring and evaluation are challenging. Some of the Public Health Outcomes Framework indicators will be impacted by the provision of high-quality green infrastructure, including indicators on air quality, the use of green space for exercise for health reasons, and the Access to Health Assets and Hazards Index.²⁹ A much wider range of indicators – for example, on physical activity, healthy weight, mental wellbeing, and social isolation – will also be indirectly affected by green infrastructure provision. Most of these indicators are only available at borough level, allowing comparisons between local authorities but not enabling more local level evaluation of impacts. Recent WHO guidance provides some suggestions of factors to consider in monitoring and evaluation, and there are toolkits for the assessment of the health-related built environment that could be adapted for the monitoring of specific local green infrastructure interventions.^30,31

Next steps for policy and practice
The 25 Year Environment Plan makes a number of specific commitments to improving green infrastructure, including proposals to produce new standards for green infrastructure, as well as to explore how national spatial data and strategies could be used to support, among other things, green infrastructure.³² The Plan sets out that government, in conjunction with Natural England and the Parks Action Group,ⁱ will develop a national framework of green infrastructure standards by summer 2019.

The 25 Year Environment Plan also makes a commitment to ensuring that the economic value of green infrastructure is adequately captured, by using a natural capital approach, as well as placing an onus on the Ministry of Housing, Communities and Local Government to look at how green infrastructure can be incorporated into national planning guidance and policy in the future. Public Health England will be working with key partners in government and related organisations in furthering the aims of the 25 Year Environment Plan.

Authors
Carl Petrokofsky is a public health specialist at Public Health England (PHE) who manages the organisation’s ‘Healthy People, Healthy Places’ programme. Flora Ogilvie worked as a public health registrar in PHE’s Healthy Places Unit, before she left the organisation earlier this year.

Footnote
i Government funding of a new Parks Action Group was announced in September 2017. See https://www.gov.uk/government/news/government-pledges-500000-for-new-action-group-to-grow-future-of-public-parks