What are nature-based solutions for infrastructure?

Nature-based solutions, also known as NbS, play an important role in meeting sustainable development goals (SDGs) and the transition to net zero. They are increasingly recognised as a cost-effective way to replace, augment, or complement traditional grey infrastructure, and for their ability to support climate resilient infrastructure.

The UN Environment Programme (UNEP) estimates that nature-based solutions can provide up to 37% of the emission reductions needed to achieve the targets of the Paris Agreement, and that they have the potential to address challenges such as land degradation and biodiversity loss. However, UNEP estimates also show that current investment in nature-based solutions must be trebled to more than USD484 billion per year to meet these objectives.

Defining nature-based solutions

‘Nature-based solutions’ is an umbrella term that encompasses a broad range of solutions. There is no one universal definition or taxonomy for these solutions, however, a common definition from the International Union for Conservation of Nature defines them as ‘actions to protect, sustainably manage and restore natural and modified ecosystems in ways that address societal challenges effectively and adaptively, simultaneously benefiting people and nature.’

Other international and regional organisations have their own definitions (e.g. The World Bank, European Commission, OECD, and Environmental Energy Study Institute (EESI)). Although definitions vary, the common attributes across most are that nature-based solutions solve a societal problem – such as climate change, water security, or disaster resilience – by the intentional use, incorporation, conservation, or restoration of nature to simultaneously provide human wellbeing and biodiversity benefits.

Taxonomies for nature-based solutions in infrastructure

Infrastructure projects that incorporate nature-based solutions are typically referred to as one of the following:

• Nature-based infrastructure
• Green or green/grey infrastructure
• Blue or blue/green infrastructure
• Hybrid infrastructure
• Natural infrastructure.

Similar to the definition of nature-based solutions, these terms can all be defined slightly differently depending on the organisation that is using them, with different or overlapping scopes of what is considered green, natural, or hybrid infrastructure. Green infrastructure relates to the built environment and is the most commonly used term, however, it is not uncommon to see these terms used interchangeably.

How are nature-based solutions used in infrastructure?

There are many types of nature-based solutions, spanning urban, rural, national, district, and community levels. As per their definition, nature-based solutions encompass both non-infrastructure and infrastructure solutions. Due to the connectedness of the natural and built environment, even nature-based solutions which are considered non-infrastructure typically also provide downstream benefits to infrastructure. E.g. forest restoration and management projects – while having direct benefits to native fauna and biodiversity – have downstream benefits for infrastructure such as reduced flooding severity and increased water quality for downstream water and energy infrastructure.

Other examples of nature-based solutions that have a direct or downstream impact on infrastructure are:

• Green roofs, urban gardens, green spaces, and bioswales: These incorporate nature into an urban environment to provide benefits such as mitigating urban heat, improving community wellbeing, and supporting better urban stormwater and flood management.
• Construction or restoration of wetlands: These offer nature-based alternatives to traditional wastewater treatment by increasing the quality of treated water and alleviating flooding.
• Implementing native mangroves to coastal environments: These use mangroves to replace or augment traditional grey infrastructure solutions such as sea walls for benefits including decreasing coastal erosion, increasing flood protection, and acting as a carbon sink to capture emissions.

Examples of nature-based solutions for infrastructure

1. The Resilient Boston Harbor Plan, US: It is estimated that severe storm surges and rising sea levels will put more than 80,000 Boston residents and USD85 billion of assets and infrastructure at risk. Costing USD30 billion over 30 years, the plan includes 765,000 m2 of new and regenerated open space to reduce these risks. The plan provides other benefits including:
   • Reducing the urban heat island effect
   • Improving air quality
   • Enhancing nature and biodiversity in the city
   • Providing retention capacity for stormwater
   • Reducing the risk of flooding along Boston’s 75 km coastline.
2. The Itaipú Preserves Program, Brazil: The Itaipú Dam is a hydropower plant that produces 90% of Paraguay’s electricity and 16% of Brazil’s electricity. Costing USD9 million from 2014–2019, the program planted more than 44 million trees in the area around the Itaipú Dam – reforesting, restoring, and conserving 101,000 hectares of land. Based on conventional alternative solutions and revenue from increased electricity generation, the program created a net present value of USD45 million in direct benefits, including:
   • Improving water quality for more efficient dam operations and for downstream users
   • Increasing climate resilience
   • Decreasing maintenance costs
   • Increasing biodiversity
   • Capturing 5.9 million tons of CO2 equivalent each year.

Implementing nature-based solutions in infrastructure

Through extensive research, the GI Hub has identified nature-based solutions as one of 15 transition pathways that can be used by governments and industry to systematically plan for infrastructure development and investment to achieve climate targets and the SDGs. However our latest data on the long-term sustainable infrastructure plans of G20 economies show there is USD168 billion planned investment into implementing nature-based solutions per year, which is well below UNEP’S estimated USD484 billion needed to meet these targets.

Closing this gap requires the integration of nature-based solutions into policy and legislations and streamlining procurement into public infrastructure projects – particularly for strategy development, monitoring, and evaluation of projects. However, the multifaceted nature of these solutions and their impact at national, district, community, and individual levels make their benefits difficult to quantify.

Decisionmakers need tools that enable them to more accurately evaluate of value and impact of these projects, particularly when compared to conventional grey infrastructure interventions, so they can better inform business cases, enable evidence-based policymaking, and accelerate much-needed public and private funding for these projects.

Our latest analysis of more than 250 long-term infrastructure plans across 25 G20 economies shows us what infrastructure investments could look like over the next few decades and where there may still be gaps. View the data