BNG: Consultations for NSIPs and Minor, Medium, and Brownfield Development Sites

On 28 May 2025, the Department for Environment Food & Rural Affairs (Defra) opened public consultations for the Biodiversity Net Gain (BNG) regimes applicable in England to Nationally Significant Infrastructure Projects (NSIPs) and Minor, Medium, and Brownfield Development sites, respectively. These two consultations welcome stakeholders' views on the proposed BNG regimes and deadline for responses is 24 July 2025. 

Proposed BNG Regime for NSIPs 

• Remit: The consultation outlines that BNG will apply to all onshore NSIPs (and components of NSIPs) in England, as far as the mean low-water mark. Offshore projects beyond the intertidal zone are excluded from the scope of the consultation and are instead governed by the Marine Net Gain statutory framework. Importantly, the new requirements will not be applied retrospectively to Development Consent Orders (DCOs) submitted or granted before the BNG implementation date for NSIPs of May 2026. Hybrid Bills are excluded from the consultation.
• Biodiversity Gain Objective: BNG will be implemented for NSIPs via biodiversity gain statements. These will outline distinct biodiversity gain objectives depending on the NSIP type and will have the effect of a National Policy Statement (NPS).   The objective can be met if there are requirements in the DCO confirming and securing this. The Secretary of State will not grant an application for development consent unless satisfied that the proposed development meets the biodiversity gain objective.
• The biodiversity gain objective does not alter existing environmental policy (including the mitigation hierarchy).
• Irreplaceable Habitat: The consultation proposes applying the same approach to irreplaceable habitats as they have applied to that of other developments, as set out in the Biodiversity Gain Requirements (Irreplaceable Habitat) Regulations 2024.
• Spatial Risk Multiplier: The consultation proposes that where a scheme crosses multiple local planning authority boundaries, NSIPs can deliver off-site biodiversity gains in any of the local planning authorities the scheme is in without incurring a spatial risk multiplier penalty. 
• Increasing Access to the Off-Site Market: The consultation proposes using the established Statutory Biodiversity Metric (subject to minor changes) for NSIPs, such that NSIP developers can purchase biodiversity units from the existing off-site market. See the Statutory Biodiversity Metric User Guide for more information. 
• Calculating BNG: The pre-development Biodiversity Value is calculated as the biodiversity value of all habitats within the entire development site boundary on the date of the DCO application, unless an earlier date is justified. The biodiversity value attributable to a development includes on-site gains, registered offsite gains and statutory biodiversity credits.  Both on-site and off-site enhancements must be maintained for at least 30 years and on-site enhancements must be secured through a requirement in the DCO, a planning obligation, or a conservation covenant.

The Government emphasises that its proposed approach strikes the appropriate balance of delivering on their ambition “to speed up the delivery of infrastructure while driving nature recovery”.  

Proposed BNG Regime for Minor, Medium, and Brownfield Development Sites

BNG became mandatory for most major developments from 12 February 2024, and for minor “small site” developments from 2 April 2024. The government has been actively seeking ways to improve the implementation of BNG, and has now turned its focus to Minor, Medium, and Brownfield Development sites.

• Remit: The consultation outlines that BNG will apply to the following works in England:
  • "Minor Development" encompassing residential development with 1-9 dwellings on a site of 1 hectare or less and commercial development with floor space less than 1,000 square meters or total site area less than 1 hectare;
  • "Medium Development" encompassing residential development with 10-49 homes on up to 1 hectare;
  • "Brownfield Development" encompassing developments on previously disturbed sites with Open Mosaic Habitat (OMH) – OMH is a high distinctiveness habitat requiring compensation on a like-for-like basis.
  • The scope of the consultation excludes householder applications, developments below the de minimis threshold, and self-build or custom-build applications.
• Extending Exemptions: A proposal is to extend exemptions for certain types of developments, particularly minor and medium-sized projects. The aim is to reduce the regulatory burden on smaller developers whilst continuing to promote biodiversity.
• Spatial Risk Multiplier:  The consultation proposes to disapply or amend the spatial risk multiplier for minor development to reduce costs and ease the process of purchasing off-site units.
• Increasing Access to the Off-Site Market: The consultation wants to improve access to the off-site market for biodiversity credits. This market allows developers to purchase credits to offset their biodiversity impacts when on-site mitigation is not feasible. Improving access to this market could provide more flexibility for developers and ensure that biodiversity gains are achieved more efficiently.
• Calculating BNG: The consultation addresses the complexity of the small sites metric. Simplifying this metric is expected to make it easier for developers to comply with BNG requirements. Likewise, the consultation acknowledges that Brownfield sites, which are previously-developed lands, present particularly unique challenges due to the presence of Open Mosaic Habitat. Tailored metrics are required to ensure that brownfield developments can contribute to biodiversity gains without facing disproportionate obstacles. The proposed changes aim to streamline the process, making it less time-consuming and more cost-effective for developers of small sites.

Concluding thoughts

The implementation of BNG has been broadly successful for larger developments, but minor developments face specific challenges. The government stresses in the latter consultation that its approach aims "to explore early opportunities to reduce process burdens, whilst still delivering measurable gains for nature". The proposed changes are designed to balance the need for economic growth with environmental sustainability. 

If you want to have your say on how the regime evolves make sure to submit a response to the consultations before 24 July 2025.

If you have any queries on the consultations or BNG generally, please contact [email protected].