By Tom Austin-Morgan

In England, BNG is mandatory, requiring developers to improve natural habitats by 10% compared to pre-development conditions. This applies to both major and minor developments and, by 2025, will extend to nationally significant infrastructure projects. Exemptions exist, but the overarching goal remains to protect and enhance biodiversity within development boundaries.

The process of BNG involves measuring biodiversity in units based on a habitat’s size, quality, and type. Ecologists assess these units before development to gauge how much needs to be replaced or improved to achieve the 10% BNG. Developers can achieve BNG through three methods:

1. On-site biodiversity creation, where habitats are improved within the development site.
2. Off-site biodiversity enhancement, either on land owned by the developer or by purchasing biodiversity units.
3. Statutory biodiversity credits, bought from the government as a last resort, with proceeds going to habitat creation across England.

This structured approach, known as the biodiversity gain hierarchy, mandates that developers first attempt on-site improvements before turning to off-site solutions or credits.

For instance, if a developer removes trees from a site, they must compensate for this loss while also delivering the mandatory 10% BNG. They conduct pre-development habitat surveys, using statutory biodiversity metrics to calculate losses and explore restoration or enhancement options. If on-site measures are insufficient, off-site biodiversity units are purchased. Failing that, the developer must resort to buying statutory credits.

Developers are also legally required to maintain any created or enhanced habitats for at least 30 years, ensuring the improvements are sustained.

BNG planning and compliance

When applying for planning permission, developers will check if their project is exempt from BNG. If not, they must submit detailed plans showing how they will achieve BNG, including significant on-site enhancements.

In some cases, a legal agreement may be required, setting out responsibilities for habitat creation, monitoring, and reporting. Developers may also need a habitat management and monitoring plan (HMMP). A biodiversity gain plan, including a metric calculation, is submitted to the local planning authority (LPA), which has eight weeks to approve or refuse it. If BNG requirements are unmet, developers face legal consequences or enforcement actions from the LPA.

Green and blue infrastructure

The Chartered Institution of Highways & Transportation (CIHT) recently highlighted the underutilisation of green and blue infrastructure (GBI) by the transport sector. GBI includes natural and semi-natural features like parks, rivers, and other eco-friendly interventions that can be integrated into urban spaces, including roads and highways. Streets and highways can play a crucial role in delivering GBI, enhancing the environment while supporting climate adaptation, biodiversity, and healthier communities.

CIHT’s report outlines key recommendations for the transport sector, urging highway authorities to:

1. Greater promotion of GBI.
2. Improved GBI guidance for local authorities.
3. Empower local authorities to implement GBI.

According to Sue Percy, CEO of CIHT: “GBI can play an important role across our highway network in promoting healthy and safe communities, as well as helping to deliver net zero targets, adapting to climate change, and conserving and enhancing the natural environment.

“Our challenge to highway authorities and other stakeholders is to make GBI a core component of their activity and at the heart of local policy.”

GBI complements BNG by integrating natural features like green spaces, water bodies, and vegetation into transportation networks. These elements can serve as wildlife habitats, facilitate species movement, and help mitigate environmental impacts like flooding and air pollution. Roadsides planted with native flora, for example, can act as pollinator pathways, while wetlands near transport routes provide natural drainage solutions.

By incorporating BNG and GBI into the design and planning stages of highways and transportation projects, developers not only meet environmental regulations but also contribute to a thriving natural world. These practices ensure that transportation infrastructure supports biodiversity, enhances natural landscapes, and creates healthier ecosystems.

Newsletter image: wild flowers on a roadside verge in Eastcote, West London; credit: Shutterstock.