On 12 February mandatory biodiversity net gain (BNG) took effect for large sites across the UK, meaning that all major developments must deliver 10% BNG, with small sites expected to join on 2 April.
Custom and self build sites that are nine-units or less and that are on a site no larger than 0.5 hectares are exempt from BNG. Exempt homes must also meet the definition of a custom or self build home, as set out in section 1(A1) of the Self-build and Custom Housebuilding Act 2015.
As set out under the Environment Act 2021, the new legislation will ensure that habitats for wildlife are left in measurably better condition that they were prior to development, resulting in a better quality natural habitat.
The biodiversity of a site is measured in units that take account of the size, quality, location and type of site, using Defra’s metric, although there is also a simpler small sites metric tool (SSM) that can be used, if the development qualifies.
The Local Government Association has considerable advice about BNG for local authorities, and states that larger scale custom and self build sites (over 9 units/0.5ha) should be dealt with in the same way as phased development. Guidance for this is set out in the Draft Biodiversity Net Gain Planning Practice Guidance.
New digital services are being prepared, such as the Biodiversity Gain Site Register, although are not yet ready, and Planning Resource points out that, currently, the Defra list of bodies able to enter net gain legal agreements consists of a single organisation.
There are also wider industry concerns that there will not be enough ecologists able to rate sites, and that local authorities are insufficiently resourced to monitor and police the scheme, complicated by the fact that on- and off-site habitats must be secured for a minimum of 30 years.
