Last reviewed 2 November 2023

From January 2024, there is a new statutory duty for biodiversity net gain (BNG) to be a condition of planning permission. Developers and local authorities share the responsibility for this, and landowners such as farmers also have a role to play. The duty is set out in s.98 and Schedule 14 of the Environment Act 2021, which amends the Town and Country Planning Act 1990. For a general overview of the regime, see Biodiversity net gain: an introduction. This article looks at some specific details that have been announced in recent government guidance.

The January deadline applies to developments covered by the Town and Country Planning Act 1990; smaller sites do not need to comply until April 2024. For nationally significant infrastructure projects, the date is 2025.

Biodiversity gain plans

Once the regulations are in force, developers who have obtained planning permission will have to submit a biodiversity gain plan describing how they propose to achieve the 10% increase to biodiversity. The plan must be approved by the local planning authority before the development can go ahead.

On 26 October 2023, Defra published a draft template for the plan, which they say is subject to change. The final template will be published before the January 2024 deadline. A separate template will be provided for small sites.

The template is accompanied by draft guidance for local authorities and developers.

Biodiversity metric

The biodiversity metric is the tool that local authorities use to calculate the biodiversity of any given site. It calculates the value of a site in “biodiversity units”. Once the authority has done this, they can work out what the 10% gain should be. The statutory metric will be laid before Parliament in November. For now, developers can use Natural England’s Biodiversity Metric 4.0. There will be a transition period when the Biodiversity Metric 4.0 can still be used. Government guidance on the metric can be found at GOV.UK.

Statutory credits

Ideally, developers will make sure that new developments enhance biodiversity by incorporating features such as ponds, hedges, green roofs or nesting boxes. However, if these are insufficient to create the necessary 10% gain in biodiversity, developers will have to invest in off-site habitats, preferably in the local area. The last resort option is to buy statutory credits from the Government, which will be invested in nationally significant habitats.

Defra published guide prices for the credits in July 2023. The final prices will be published in November. The cost depends on the distinctiveness of the habitat. For example, a credit for grassland costs £42,000, while for a lake it rises to £125,000. Developers must buy two credits for every biodiversity unit they need to compensate for. The credit sales service will be available once BNG becomes mandatory.

Help for local authorities

BNG presents quite a challenge for local authorities, though many are already making BNG a condition of planning permission. Researchers from Oxford found “numerous issues, including basic errors in metric calculations, and infeasible habitat creation proposals”. The researchers have therefore put together a guide for local authorities on what to do when a BNG plan is put forward for a new development.

The Government is providing £9 million in extra funding for local authorities so that they can employ ecologists and other specialists.

Guidance for landowners and managers

Landowners such as farmers can sell off-site biodiversity units to developers. Off-site units are from land which is not within the development, but may be nearby. This does not mean that they sell the land. Instead, they enhance an area of land to create habitats and improve biodiversity, and the developers fund this. Landowners who wish to sell biodiversity units will first need to find out what habitats are needed in their area. Then they will need to engage an ecologist to calculate how many biodiversity units the land can provide. The up-to-date government guidance can be found at GOV.UK.

Off-site biodiversity units must be maintained for at least 30 years and will be listed on the biodiversity gain sites register, which will launch in November. The listing will include the relevant developments.

Landowners can enter into “conservation covenants” with the local authority or another body whose main purpose is conservation. The covenant is an agreement stating what the landowner and the local authority/other body will do to conserve valuable features of the land, which can include buildings as well as natural habitats. For example, a farmer may agree to refrain from using pesticides on native flora. This is one way in which landowners can ensure they are paid for achieving BNG. The guidance on conservation covenants can be found at GOV.UK.

Croner-i will publish a further update on BNG once the legislation comes into force.