FAQ

Defra have confirmed that the mandate will be effective for all large domestic, industrial, commercial and mixed-use sites from January 2024. More time has been given to Small Sites (April 2024) and Nationally Significant Infrastructure Projects (NSIPs) scheduled for November 2025.

The purpose of the biodiversity gain plan is to provide a clear and consistent document with which a developer sets out how the proposals meet the biodiversity net gain objective. It contains the relevant information for the planning authority to determine whether the BNG objective has been meet. The current draft template can be found here.

Section 3.1 of the Government’s 2023 consultation response sets out exemptions from mandatory BNG, which will be implemented via secondary legislation:

• Development impacting habitat of an area below a ‘de minimis’ threshold of 25 metres squared, or 5m for linear habitats such as hedgerows and watercourses [NOTE Defra have confirmed (9 August 2023) that this is 25 squared metres (5m x 5m = 25 sqm)]

• Householder applications

• Biodiversity gain sites (where habitats are being enhanced for wildlife)

• Small scale self-build and custom housebuilding.

The de minimis threshold applies to the area or length of habitat within a development, not the total development footprint, and the same exemption will apply for small sites. If a development contains less than 25m2 of non-priority habitat but 5m or more of linear habitat, or vice-versa, then the exemption will not apply and all habitats would be subject to BNG. If the exemption does apply then there is no requirement to deliver BNG on that site.

Statutory biodiversity credits should be considered a last resort option for developers if you are unable to use on-site or off-site units to deliver biodiversity net gain (BNG).

You will be able to buy statutory biodiversity credits using a credit sales service, which will be available once BNG becomes mandatory. Indicative prices can be found here.

Under the mandatory BNG approach, biodiversity units refer to the output of the biodiversity metric. The metric uses habitats and ‘biodiversity units’ as a proxy to describe biodiversity. These biodiversity units are the ‘currency’ of the metric.

There are three types of biodiversity units, which are calculated in three separate ‘modules’ of the metric (area units, linear units and watercourse units).

Off-site biodiversity units can be sold, i.e. ‘1 unit of modified grassland costs £xx', but should not be referred to as credits to avoid confusion with statutory credits.

Where the brownfield site’s baseline habitat value is 0 units following an ecological survey, no. However, some brownfield sites can house Open Mosaic habitats over time which will have an ecological value, so it is always worth carrying out a survey.

No, this will be fixed and set in planning policy as such.