As the impacts of the climate and biodiversity emergencies become clearer, there is a growing need to rethink how infrastructure is developed and managed in the UK. The planned redundancy of concrete and steel as building materials makes sustainable urban development problematic. However, the EU, via their Nature-Based Solutions (NBS) research programme, and the UK government, through the Environment Act (2021), and its Biodiversity Net Gain (BNG) legislation, have attempted to transition towards a more resilient approach to development. In this article, Professor Ian Mell outline how the promotion of green infrastructure (GI) as an essential form of urban infrastructure is a key component of this debate.

• GI can offer alternative pathways to future-proof cities via more adaptive forms of infrastructure investment.
• Environmental advocates have called for GI to be considered as essential infrastructure.
• Urban GI can save on health costs, lower temperatures and reduce pollution.

The role of green infrastructure

GI has been identified as a go-to form of sustainable investment since the late-1990s, due to its promotion of increased quality, quantity, functionality, and accessibility of nature within urban areas.

However, an ongoing reluctance is visible within built environment discussions among planners, developers and engineers who contest the long-term functionality of ‘nature-based’ interventions, compared to those associated with the delivery of property or transport infrastructure.

Unfortunately, the functional lifespan of much man-made urban infrastructure is now leading to failures, and politicians and urban planners are searching for new ways to regenerate the existing urban fabric.

Returns on investment

Increased extreme heat, rainfall and drought events, and the subsequent impact on urban liveability and environmental functionality have led environmental advocates to call for GI to be considered as essential infrastructure. The introductory chapter of the Institute of Chartered Engineers (ICE) Manual of Blue-Green Infrastructure, for example, calls for GI to be reclassified as an essential form of infrastructure. The ICE, and others, argue that continuing to develop cities without an explicit focus on nature may be a fool’s errand that undermines the sustainability of urban areas.  By emphasising an ecological focus in master planning, increasing the proportion, diversity, and functionality of urban ecosystems, and working with water and climate specialists, cities can rethink how to align socio-cultural and politico-economic systems with ecological ones.

Numerous examples exist illustrating the return on investment that GI provides for cities including:

• £2.1 billion per annum could be saved in health costs if everyone in England had good access to greenspace, due to increased physical activity in those spaces.
• Research by CE Delft and the European Public Health Alliance found air pollution costs London £10.32 billion per annum in total, or £1,173 per year per person.
• Urban GI can lower ambient air temperatures by between 1.8^oC – 8^o
• GI is effective at reducing peak discharge in 80% of frequent storm events.
• Up to 84% of energy costs could be saved by the cooling effect of green roofs, and 64% for green walls (climatic and building content dependent).
• i-Tree analysis for London states that the city’s street trees support energy saving in buildings, increase property prices by 15%, remove 561 and 1680 tonnes of pollution from inner and outer London per annum respectively, and provide 499,000 and 1,868,000 tonnes of carbon storage per annum for inner and outer London, respectively.

Current approaches and strategies

The grouping of such evidence has shaped the UK’s promotion of Biodiversity Net Gain (BNG) (and the Biodiversity Metric 4.0 to deliver it), Local Nature Recovery Strategies (LNRS), and the National GI Standard Framework, establishing them into positions of prominence.

Each of these approaches places an explicit value on nature as an essential infrastructure, requiring a more strategic approach to ecological provision. This is established via a minimum 10% increase in biodiversity delivered via BNG, and adherence to the Urban Green Factor (UGF) metric and design principles in the GI standard framework.

BNG, for example, states that it “…makes sure that habitats for wildlife are left in a measurably better state than they were before the development”. The application of BNG aims to deliver biodiversity enhancement either on-site, off-site or as a combination of both,  depending on circumstances.

Likewise, the National GI Standard guidance calls for local government, developers, and land managers to support the delivery of green and blue spaces that are accessible, of high quality, and multi-functional. Moreover, the ongoing use of the UGF in the City of London, as well as in Swansea and Southampton, has shifted the emphasis of planning considerations to GI being a ‘must-have’, not a ‘nice to have’ form of infrastructure. Without the inclusion of GI, planning permissions are less likely to be granted.

The increased emphasis on nature as an essential form of infrastructure has emerged due to ongoing advocacy work from Natural England, England’s Community Forest Partnerships, the environment sector more broadly, local government, and academics. Each of these have provided compelling evidence of the added ecological and socio-economic value that investment in GI can deliver.

Recommendations for essential GI

To successfully transition towards a more resilient form of urban development requires more than evidence. It is also critical that the new UK government engages effectively with research if they are to develop policies that support ecological functionality.

The government should implement the following changes to achieve resilient urban development:

• The Government should legislate GI within law as ‘essential infrastructure’ thus giving it an equal prominence as other forms of investment in development debates.
• Labelling GI as essential infrastructure would complement the current legal protection afforded to the environment by the Environment Act (2021) and Biodiversity Net Gain (BNG) requirements by ensuring that greening (it’s in widest sense) is embedded within all future policy and legislation.
• Providing a legal guarantee that GI is considered as essential infrastructure would require the Treasury, the Ministry of Housing, Communities and Local Government (MHCLG), and the Department of the Environment, Food and Rural Affairs (Defra) to allocate the appropriate funding to support investment.

These pathways require government at all scales to continue to evolve their thinking regarding the inclusion of environmental quality, quantity, and functionality within future strategic planning and delivery plans.