Biodiversity Net Gain

Biodiversity Net Gain

What is Biodiversity Net Gain?

Biodiversity Net Gain (BNG) is a legal requirement for all non-exempt planning applications to demonstrate a 10% net gain for biodiversity.

Introduced as part of the Environment Act 2021, BNG is intended to contribute to tackling the nature crisis currently underway in the UK. As detailed in the State of Nature Report 2023, the UK is now one of the most nature-depleted countries on Earth. In the context of Surrey, the State of Surrey’s Nature Report estimates that 1 in 9 species native to the county are now locally extinct. By mandating developments to demonstrate measurable net-gains for biodiversity, BNG creates a legal requirement for habitat creation and enhancement. The result is intended to contribute to ‘more, bigger, better and joined up’ habitats in line with the Making Space for Nature Lawton Review 2010 and the creation of a resilient ecological network that will allow species to recover.

State of Nature 2023 - report on the UK’s current biodiversity

This webpage is intended to supplement the nationally published resources for BNG and Surrey County Council's local list of validation requirements.

How is BNG measured?

BNG uses the Statutory Biodiversity Metric Calculation Tool to quantify the value of a site’s habitats using ‘units’ that reflect their relative ecological importance. By comparing the unit values of a site’s existing baseline habitats with its proposed post-development habitats, the net change in value can be calculated. For a full outline of the method and the rules which must be complied with for statutory BNG, applicants should refer to the Statutory Biodiversity Metric User Guide on the Government website.

Surrey County Council requires a minimum 10% net gain consistent with the national statutory minimum. However, applicants should be aware that this can vary across the Districts and Boroughs within Surrey who may have specific policies within their Local Plans that require a higher percentage of BNG to be achieved. If an application falls within a Local Authority area, where a higher percentage net gain target is required by a Development Plan policy this will need to be met within the application. View the District and Borough policy pages.

Pre-application advice

BNG is new, nuanced and site specific. We strongly encourage applicants to engage with the County Council’s pre-application planning advice service to discuss any BNG queries ahead of making a planning application. View the Pre-application discussions for planning applications guidance.

What to submit with a Planning Application

The Government sets out clear minimum requirements for what information an applicant must provide when submitting a planning application. The minimum requirements are found within the Biodiversity net gain: what local planning authorities should do government webpage.

Each Annex of Surrey County Council's local list of validation requirements sets out the information requirements expected to be submitted with each application type (Minerals, Waste and Regulation 3 Development). Whilst the statutory minimum requirements for information are limited the County Planning Authority needs be a confident when determining the application that the biodiversity gain condition is capable of being discharged and the biodiversity gains can be delivered.

Additional information may therefore be requested at the planning application stage where there is uncertainty over the capability of the biodiversity gain condition being successfully discharged. The primary reasoning for this could be:

• To have confidence that the Biodiversity Gain Plan will be capable of being successfully discharged post-consent;
• To sufficiently inform any legal agreements or planning obligations that may be required to secure BNG (see on-site significant enhancements);
• To streamline the discharge of the pre-commencement BNG condition;

Exemptions

Some types of planning application are exempt from BNG, these are outlined in full detail on the Government website for biodiversity net gain and exempt developments.

If applicants wish to claim an exemption, they must submit a supporting justification statement which evidences that their scheme is exempt. Please reference our Local List for further detail.

Significant on-site enhancements

Significant on-site enhancements are defined as ‘areas of habitat enhancement which contribute significantly to the proposed development’s BNG, relative to the biodiversity value before development’. The creation and maintenance of these significant enhancements must be secured with a legal agreement (planning obligation or conservation covenant) or planning condition for 30 years. The most appropriate mechanism to secure BNG will be agreed during the determination of the planning application.

The Government list of what may count as significant is outlined and listed below on the Make on-site biodiversity gains as a developer webpage.

Strategic Significance and the Local Nature Recovery Strategy (LNRS)

Strategic significance is one of the mandatory habitat quality multipliers applied within the statutory biodiversity metric calculation tool. For a full outline of all the multipliers, applicants should refer to the Statutory Biodiversity Metric User Guide on the Government website.

The strategic significance multiplier provides a ‘boost’ to the unit value of habitats where they are identified as being locally important for nature conservation. It is divided into three categories: high, medium and low. This multiplier is linked closely with the Local Nature Recovery Strategy (LNRS) and different rules apply before and after the LNRS is published (please see tables 7 and 8 in the Statutory User Guide).

Post-LNRS Publication

As of 31st March 2026, Surrey’s LNRS has been published. This document now determines the use of the strategic significance multiplier for all applications submitted after this date. In line with Table 7 of the statutory user guide, habitats should be assigned ‘high’ strategic significance if they align with the mapped potential measure in the Local Habitat Map. Any sites located outside of the LNRS can only be referenced as ‘low’ strategic significance. The ‘medium’ strategic significance category is no longer applicable post publication of the LNRS.

For full details and the latest updates on the Surrey LNRS, applicants should refer to the Local Nature Recovery Strategy webpage.

Pre-LNRS: Publication

For applications submitted to Surrey County Council before publication of the LNRS, the documents to use when determining the strategic significance multiplier are the objectives and targets documents for Surrey’s Biodiversity Opportunity Areas (BOAs). Surrey has 50 individual BOAs that are grouped into their respective National Character Areas (NCAs). BOAs ‘represent a targeted, strategic approach to conserving and enhancing biodiversity, and form the spatial basis for planning Surrey’s ecological network.’ BOAs comprise a combination of designated sites for nature conservation and also undesignated areas containing priority habitat types (as listed under Section 41 of the Natural Environment and Rural Communities Act 2006). For further detail on BOAs, please see the BOA Policy Statements published by Surrey Nature Partnership.

Pre-publication of the LNRS, the strategic significance multiplier should be applied as follows:

• You should apply the High strategic significance category to habitats in the baseline sheets if your site is within a BOA and the habitat type is specified within that BOAs restoration / creation targets.
• You can apply the High strategic significance category to habitats in the post-intervention sheets if your site is within a BOA and the created or enhanced habitats are those specified within the BOAs restoration / creation targets

Where the definition for high strategic significance is not met, low strategic significance must be applied. The medium strategic significance multiplier can only be applied when the Local Planning Authority (LPA) has not identified a suitable document for assessing strategic significance.

Biodiversity Duty Report

In addition to provisions for BNG, under the Environment Act 2021 public authorities are required to consider what they can do to conserve and enhance biodiversity in carrying out their functions and to publish a report setting out how they have met this duty. Surrey County Council has now published its first Biodiversity Duty report, marking a significant milestone in our commitment to addressing biodiversity loss across the county.

This report brings together information from teams from across the council setting out the relevant activities and policies that have conserved and enhanced biodiversity. The report sets out work spanning habitat creation, species monitoring, land management improvements, and BNG. The details contained in the report clearly show how the Council has conserved and enhanced biodiversity across its functions.

Surrey County Council has set ambitious targets for the next reporting period, building on the foundations laid during this first phase. Planned activities include expanding habitat connectivity across our landholdings, deepening partnerships with local nature recovery networks, and embedding biodiversity considerations further into our decision-making processes. Local Government Reorganisation will have a significant impact on how activities and policies develop over the next reporting period.
Please see here for our published report.

For further details on the published Biodiversity Duty Report (PDF)

Files available to download

• Biodiversity Duty Report (PDF)
  Surrey County Councils Biodiversity Duty report. Describes actions taken for biodiversity between January 2024 to 2026. Required by Environment Act 2021