Biodiversity Net Gain FAQs

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Since February 2024, most new planning permissions in England have been subject to a pre-commencement condition requiring a 'biodiversity gain plan' for the development.
UK Real Estate and Construction
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Since February 2024, most new planning permissions in England have been subject to a pre-commencement condition requiring a 'biodiversity gain plan' for the development. In this section of the Spring Briefing, we answer some frequently-asked questions about the new regime.

1 Which developments are affected?

Most developments are within scope if the relevant planning application was made after 12 February 2024. The main exceptions to this are:

  • 'Nationally Significant Infrastructure Projects', which are expected to be subject to a BNG requirement from 2025;
  • Developments which do not impact priority habitats and affect less than 25 square metres of habitat or 5m of linear habitat like hedgerows; and
  • Householder applications and self-build applications.

2 What does 'biodiversity gain' mean?

Biodiversity net gain (BNG) is a radical new planning requirement whereby the biodiversity value attributable to a new development exceeds the pre-development biodiversity value of the onsite habitat by at least 10%. In simple terms, it aims to leave the environment in an improved position post-development than it was before.

3 How is biodiversity gain measured?

Using the Government's biodiversity metric. Biodiversity is measured using a statutory biodiversity metric which assesses the biodiversity value of habitats by calculating how many units a habitat contains before development takes place and how many units are needed to replace the units of habitat lost and to achieve 10% BNG through the creation or enhancement of habitat. The formula takes into account a range of factors including the habitat's size, type, condition, and strategic significance.

4 How should biodiversity gain be delivered by developers?

This value can be delivered on-site, off-site, or through the purchase of 'biodiversity credits', or via a combination of these. There is a hierarchy, with on-site value being the preferred option where possible. Failing that, off-site options should be explored next followed by the use of credits as a last resort. The associated habitat, or enhancement, must then be maintained for at least 30 years following the completion of the development with this obligation being secured by legally binding mechanisms such as a conservation covenant.

5 What might on-site gains involve?

The delivery of BNG can range from the creation on the development site of new habitats such as chalk grasslands or meadows through to smaller enhancements such as the installation of bee bricks and green roofs. They will be calculated by reference to the current Biodiversity Metric 4.0. BNG delivery can also be achieved in the construction of the built environment itself, through the inclusion of infrastructure like solar slate, ground source heat pumps, composting areas, and rainwater collection.

6 What might off-site gains involve?

If a developer cannot achieve the 10% BNG by creating and enhancing on-site habitats, they must buy off-site units in addition to any on-site gains they can achieve. The biodiversity metric incentivises off-site gains close to the development, so off-site gains in a neighbouring LPA will be worth fewer biodiversity units than off-site gains in the same LPA as the development, and if they are further away than the neighbouring LPA then they are worth even less. This aims to ensure as close a connection between the development and the BNG as possible. The metric also incentivises off-site biodiversity gains in areas of strategic significance as defined in the relevant LPA's local nature recovery strategy. In terms of the practicalities of delivering off-site gains, these can either be achieved by:

  • buying off-site units from a landowner or, if available, from a habitat bank operator, a broker, a trading platform or the local LPA; or
  • delivering off-site gains on land elsewhere that is owned by the developer. The developer will have to comply with the rules for land managers.

Whichever route is followed, the gain site must be registered on the biodiversity gain sites register. This is intended to show the location of biodiverse land and to stop 'double counting' of sites in respect of multiple developments.

7 Has the introduction of the new regime had any impact on the speed, cost or uncertainty of the planning system?

It is probably a little too early to say. However, there are certainly well-founded fears over the introduction of such a significant new requirement, which brings with it a new area of complexity and need for expertise within LPAs. Delays feel almost inevitable given that the planning system already creaked under the weight of expectations before the introduction of the BNG requirements.

8 How should developers tackle BNG requirements?

It will be important to frontload the consideration of BNG requirements, giving them due consideration right from the inception of a development proposal. They should influence site selection, the application deadline, scheme design and the structuring of the application, following through to its submission and beyond. Constructive collaboration with the LPA throughout will also be critical.

The submission of the Biodiversity Gain Plan, pre-commencement, should represent the culmination of all that work. If frontloaded, it should help to reduce the scope for unexpected delays in the condition being discharged and, consequently, starting on site.

9 Is there any Government guidance about the BNG regime?

Yes, there is a collection of useful guidance notes here.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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