Biodiversity Net Gain: Consultation Open for NSIPs and Minor, Medium and Brownfield Development

The Department for Environment, Food & Rural Affairs have just opened two separate consultations - Biodiversity Net Gain (BNG) for Nationally Significant Infrastructure Projects (NSIPs) and Improvements to BNG for Minor, Medium and Brownfield Development.

Both consultations close at 11:59pm on 24th July 2025.

NSIPs Consultation

BNG requirements for Nationally Significant Infrastructure were originally anticipated to commence from November this year, however, they have now been delayed until May 2026. Nevertheless, the consultation documents provides a glimpse of future BNG requirements for NSIPs. The consultation is seeking views on the model text contained within the consultation document. There is a lot to take in and it is essential reading in its entirety!

Initial points to note include:

• Biodiversity Gain Plan Submission: a Biodiversity Gain Plan must be submitted with the Development Consent Order (DCO). While final details, such as off-site gain allocations or proof of credit purchases, can be provided post-consent, most biodiversity units (including off-site units and credits) should be secured before development begins. Any remaining shortfall can be addressed once the final impact on habitats is fully assessed.

• Irreplaceable Habitat: the same approach to irreplaceable habitats used in other developments will apply. It remains to be clarified whether the model text and the current Biodiversity Metric User Guide offer sufficient guidance for NSIPs or if additional information is required.

• Pre-Development Baseline Dates: an earlier baseline date must be used in cases where on-site activities have taken place since 30th January 2020 outside of permitted planning regulations or where a site has been cleared under an existing permission but the development has not yet been built.

• Temporary Land Use and Bespoke BNG Approaches: there is ongoing consideration of tailored BNG approaches for temporary land use, particularly where the standard 30-year longevity requirement may not be practical or achievable.

• Phased Development: provisions are being made for a phased approach to BNG, accommodating developments delivered in distinct phases.

Minor, Medium and Brownfield Development Sites Consultation

The Ministry of Housing, Communities & Local Government have released a Planning Reform Working Paper: Reforming Site Thresholds today (28th May 2025) which proposes reforming site size thresholds for residential development and introducing medium development sites as follows:

• Minor Residential Development – fewer than 10 homes /up to 0.5 hectare (ha).

• Medium Residential Development – between 10-49 homes/up to 1.0 ha.

• Major Residential Development – 50+ homes / 1+ hectare.

The proposed improvements aim to ensure that the Biodiversity Net Gain (BNG) framework is proportionate for Small and Medium Enterprise (SME) developers. This appears to have prompted the creation of a new ‘medium development’ category.

The consultation outlines a range of potential reforms to better support SMEs within the BNG framework, including:

• Replacing self-build/custom build exemption with single dwellings or extending exemptions to all minor developments, with possible higher de minimis thresholds.

• Potential new exemptions for parks, public gardens, playing fields and developments with a primary biodiversity conservation or enhancement objective.

• Extending the de minimis exemption to larger development footprints (50m², 100m², 250m² or other thresholds).

• Amendments to the small sites metric, including:

  • Removing trading rules.

  • Refining habitat condition assessments.

  • Simplifying habitat definitions and guidance.

  • Improving competency requirements for habitat identification.

• Adjustments to the standard metric for minor developments where watercourses are involved.

• Digitisation of the main metric with the aim to make it more accessible and efficient.

• Encouraging biodiverse features, such as bird boxes, to be included in developments.

• Greater flexibility to go off- revision to the on-site first hierarchy.

• For brownfield sites, updates to open mosaic habitat (OMH) definitions, including improved guidance and assessment criteria for ecologists, and allowing alternative habitat mosaics when off-site OMH replacement is unfeasible.

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Need help navigating the new reforms? At Bluestone Planning, we recognise the pivotal role these changes will play in shaping development opportunities. If you currently possess land and are uncertain about how to proceed in light of policy reform, we are here to help. Our team is ready to guide you through these new rules and help you make the most of the opportunities they present.

Contact us at Bluestone Planning by calling +44 1235 766825 or emailing admin@bluestoneplanning.co.uk.