For Biodiversity Net Gain (BNG) participants across England, whether unit suppliers or buyers, the clock has been ticking towards a new challenge, navigating the shift to Local Nature Recovery Strategies. Many have now been published, while many others have not.
We are currently in a pivotal BNG transition period where many developers and Local Planning Authorities (LPAs) may not realise they operate in a state of regulatory limbo. While the mandatory BNG framework is live and established, the full weight of local priority mapping is yet to be felt.
Central to this shift is the impact of LNRS publication on the Strategic Significance multiplier within the Statutory Biodiversity Metric. This multiplier serves as the primary incentive for targeted habitat creation. Biodiversity metric calculations must now adapt during this interim phase, as the rules fundamentally pivot once an LNRS is published.
The ‘Relevant Date’ Rule
A critical influence on the BNG requirements, and hence costs, for any prospective development is the date-stamping of pre-development biodiversity baseline values. For planning applications made under the Town and Country Planning Act, a site’s baseline value is determined on the ‘relevant date’, which is typically the date the planning application is submitted.
If a planning application is submitted at a time when there is no published LNRS covering the site area, then the baseline is calculated using the interim rules laid out in the statutory metric user guide. Even if the local authority publishes its formal LNRS shortly after submission, the baseline strategic significance remains unchanged. From a developer’s viewpoint, this is a vital safeguard that prevents retrospective value-stripping, ensuring that they can rely on their initial valuations without fear of mid-process BNG baseline inflation.
Live Applications Must Adapt
While the baseline is frozen, the post-development side of the metric remains dynamic and must reflect the projected value of the habitat at the time the development is completed.
That means that if an LNRS is published before an application is determined, or after permission is granted but before the Biodiversity Gain Plan is submitted, the post-development Strategic Significance multipliers must be reassessed.
It is these Strategic Significance multipliers that could result in unit calculations changing.
Case Study: The Reassessment Timeline
- February: Application submitted (no LNRS published).
- May: Planning permission granted.
- June: LNRS is formally published.
- July: Developer prepares to submit the Biodiversity Gain Plan.
In this instance, the developer must reassess the post-development Strategic Significance multiplier to align with the new LNRS mapped measures. This is not a simple clerical update; it may require a comprehensive revision of the metric calculations. Such shifts may necessitate design modifications, or adjustments to planned purchases of off-site biodiversity units from a habitat bank, to ensure the 10% BNG threshold is still met.
A New Binary for Strategic Significance
The publication of an LNRS marks the end of the middle ground. In the pre-publication phase, users of the statutory biodiversity metric follow Table 8 in the User Guide, which allows for High, Medium, and Low strategic significance categories. Once an LNRS is published, Table 7 takes precedence, and the Medium category becomes redundant.
The metric moves to a strict, high-stakes binary:
- High (1.15x Multiplier): Awarded only to post-development habitats that meet the Table 7 criteria, specifically those consistent with the mapped measures and priorities identified in the local habitat map.
- Low (1.0x Multiplier): The default for all baseline habitats and any post-development habitats that fail to meet the specific High criteria.
Expert Pro-Tip: Split Parcels
Accuracy in the metric is paramount. Where habitat parcels are intersected by a boundary between two different strategic significance zones, these parcels must be split within the metric tool. It is important to note that this is a spatial data requirement; the metric tool cannot automatically detect or perform these splits for you. Consultants should ensure that GIS data is prepared correctly. Failure to do so can lead to inaccurate unit counts and potential delays in discharging the BNG condition.
Mapped Measures
The LNRS is designed to guide nature recovery decisions, directing the market toward the most ecologically valuable interventions. By identifying mapped measures, it provides the mathematical unit uplift necessary to commercially incentivise locally desirable nature recovery.
The strategic significance multiplier rewards alignment with these local priorities, ensuring that the right habitats are created in the right places.
The Path Ahead for Nature Recovery
Defra guidance provides the essential roadmap for this transition. While the relevant date rule offers developers a stable baseline, the requirement to reassess post-development values against a live LNRS ensures that BNG remains a responsive tool requiring attention throughout the planning process.
As we move through 2026, the Strategic Significance transition period is ending as local strategies go live across the country. This shift replaces previous flexibility with a stricter ‘High or Low’ system. The primary risk for developers today is the gap between a planning application submission and the final Biodiversity Gain Plan. If a local strategy is published in that window, a project’s BNG requirements can shift unexpectedly.
CSX is here to help developers navigate this, by spotting these risks early and ensuring the path to meeting the BNG requirements remains predictable, stable, and free from late-stage delays, compliance issues or budget shocks. Please do reach out if we can be of any assistance.