From 2 November 2026, biodiversity net gain (BNG) will become mandatory for new nationally significant infrastructure projects (NSIP) in England.

Department for Environment, Food & Rural Affairs (Defra) has published guidance setting out how BNG should be considered throughout the design and consenting process. The guidance builds on the final biodiversity gain statements and initial guidance published earlier this year.

The first phase of BNG reforms for smaller sites, including the 0.2 hectare exemption, came into force on 6 August 2026. 

Work is underway on the second phase of reforms which include:   

• an exemption for development whose primary objective is to conserve or enhance biodiversity   
• a targeted exemption for development that enhances parks, playing fields and public gardens   

Defra is also set to make some changes to the statutory biodiversity metric. These include measures to address some of the specific challenges that BNG can pose for brownfield developments with open mosaic habitat, and changes to the way spatial risk is assessed for area habitats by using Local Nature Recovery Strategy areas only.