NSIPs – an overview of the rules

What Are the BNG Rules for NSIPs?

BNG will soon be mandatory for all Nationally Significant Infrastructure Projects (NSIPs). On the 2nd November 2026 all Development Consent Order (DCO) applications will have to deliver a minimum of 10% net gain in biodiversity.

The rules for NSIPs will be similar to mandatory BNG, which is already in place for all other developments in England. The Statutory Metric will still be used to calculate biodiversity units, as well as the way habitats have to be recorded, managed and monitored for a minimum of 30 years.

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BNG for NSIPs – the Key Points

1.     On-site and off-site gains will be considered the same within the DCO application process.

2.    On-site and off-site gains will have to be secured by a legal agreement.

3.    All off-site gain sites will be recorded on the register as well as allocations to developments as per the BNG guidance.

Due to the scale of NSIPs some guidance already published sets out a slightly different approach. The biggest difference is the habitats you can count towards your baseline. Guidance states that if a habitat is not negatively impacted by the development, then it does not have to be included within the baseline and will therefore not be included as part of the net gain calculation. Furthermore, spatial risk is considered over the whole BNG Boundary of the site even where it covers multiple NCA or LPAs. This means that off-site units can be purchased within any LPA or NCA covered by the site without penalty.

Which NSIPs are covered by BNG?

All NSIPs will be covered by the new guidance apart from marine habitats (habitats below the mean low water mark). Developments such as offshore wind farms and undersea cables will be exempt, but any terrestrial development that is associated with these applications will be covered by mandatory BNG. Furthermore, if there are any cross-border sites, only the habitats in England will be counted in the baseline and can deliver gains. Finally, infrastructure being delivered by other means – such as Hybrid Bills – will be exempt from mandatory BNG.

To read the detailed NSIP guidance, see: https://www.gov.uk/guidance/biodiversity-net-gain-nationally-significant-infrastructure-projects.

How to calculate your BNG baseline for NSIPs

As per the BNG guidelines, the baseline biodiversity valueof the site must be calculated using the Statutory Biodiversity Metric.

Your BNG Baseline should include:

• Habitats contributing to your on-site net gain: habitats to be enhanced to another habitat type or improved in condition; or the habitats that will form the baseline of newly created habitats.
• Habitats negatively impacted: these should include lost habitats and habitats which will drop in condition due to the development.
• Habitats impacted but counted as retained: habitats can count as retained if reinstated to their original condition
  
  • within 5 years for low or very low distinctiveness habitats.
  • within 2 years for medium distinctiveness habitats.

Habitat areas within the red line that are retained or not being used to count towards a biodiversity gain will not have to be included within the baseline. The habitats can only be excluded if they will not be temporarily or permanently removed, or if they will not experience a reduction in condition during works or post development.

Below ground infrastructure will not have to be included within your baseline, as long as no habitats above are disturbed or negatively impacted by the works. Furthermore, habitats below above-ground infrastructure – such as powerlines – will not need to be included but other areas such as around pylons or construction compounds will need to be included.

Find out more about what to include in your baseline here: https://www.gov.uk/guidance/what-to-include-in-biodiversity-net-gain-baselines-for-nsips.

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