Mandatory biodiversity net gain requirements for all planning applications

Biodiversity net gain (BNG) is now mandatory for all new planning permission applications. This has been the case for major developments since 12 February 2024 and small sites since 2 April 2024.

What BNG is for

BNG contributes to the recovery of nature whilst developing land. BNG also makes sure that habitat for wildlife is in a measurably better state than it was before development.

Exemptions

To check if your development is exempt, please see the government’s list of exemptions.

If you think your development is exempt from BNG, you still need to provide a biodiversity statement specifying the reason for the exemption and including any evidence to support this position.

Existing protections and legislation

BNG does not change existing biodiversity protections, statutory obligations, or policy requirements. BNG is in addition to existing wildlife legislation and policy that, for example, prevents harm to habitats and wildlife and requires biodiversity enhancements. 

Applications exempt from BNG will still be subject to this existing policy and wildlife legislation and these applications are still expected to demonstrate their potential impacts on biodiversity either on or adjacent to the development site, how this will be mitigated as well as provide biodiversity enhancements onsite.

Requirements

All developments subject to BNG must demonstrate how the development site meets the minimum mandatory requirement of 10% BNG over the pre-development value of the site.

The minimum information that you must submit is set out in paragraph 11 of the Biodiversity Net Gain Planning Practice Guidance. Some of these requirements are also included in the standard application form available on the Planning Portal. 

Statutory biodiversity metric

For all major developments and small sites where certain habitats and species are present, one of the key requirements is to complete and submit the Statutory biodiversity metric calculation tool.

The metric must be completed by a competent person with specialist knowledge of habitat types and conditions, such as a qualified ecologist, who is a registered member of the Chartered Institute of Ecology and Environmental Management (CIEEM) and can advise on the calculations.

Small sites

For small sites not subject to the exceptions listed below, applicants can complete and submit the Small sites metric. This metric needs to be completed by a competent person but does not need to be an ecologist. See the Small Sites Metric User Guide for the definition of a ‘competent person’. The statutory biodiversity metric calculation tool can always be used in its place.

Small sites required to complete the statutory biodiversity metric are as follows:

• Small sites containing any habitats (including riparian zones where relevant) that are not available in the SSM
• Small sites where priority habitats are present (some hedgerows and arable field margins are excluded from the above as these are medium distinctiveness habitats and are included in the SSM)
• Small sites where protected sites or habitats are present
• Small sites where European protected species are present

If statutory protected sites or priority habitats are located within 500m of the development site boundary, you should also consider whether you need to contact an ecologist and use the statutory biodiversity metric calculation tool.

If the user chooses to continue to use the SSM, a section of the calculation tool must be filled in to reflect this and a warning flag will appear where this is the case. 

Mitigation hierarchy

The biodiversity metric has been designed to follow the mitigation hierarchy and support the retention of valuable habitats. The hierarchy seeks to avoid and then minimise impacts to habitats, before mitigation and/or compensation for a development is sought.

Developers must try to retain and protect existing habitats where possible and where necessary mitigate and compensate for any impacted habitats as well as provide all biodiversity net gain onsite. 

Where this is not possible, more costly offsite units and/or statutory credits will have to be purchased, and the onus will be on the developer to explain why and provide evidence for why the scheme cannot be amended to retain the biodiversity onsite.

Recommended additional information 

The government has encouraged local planning authorities to request additional information beyond the minimum national information requirements, to help process planning applications subject to BNG.

Therefore, it is strongly recommended that applicants supply:

• A fully completed biodiversity metric (including both the pre-development baseline and post-development calculations)
• A to scale plan (with a north arrow) detailing the proposed post-development BNG habitats

Providing the above two documents from the outset will save you expending further time and resources having to provide additional documents to evidence your BNG.

In addition to the above, for applications where BNG applies, it is also recommended to:

• Use the statutory metric as early as possible in the site design process to help avoid biodiversity loss
• Follow the biodiversity gain hierarchy which prioritises onsite BNG first
• Consider how BNG and the London Plan’s Urban Greening Factor policy G5 can be optimised at design stage. Meeting UGF can contribute towards the achievement of BNG
• Consider how the location of onsite biodiversity relates to adjoining habitats, green corridors or existing green space within the site and beyond the red line boundary
• Consider how suitable multi-functional biodiversity enhancements can form part of the site’s landscaping and amenity space strategy
• Check whether your site is in or close to a designated park, open space or Site of Importance for Nature Conservation (SINCs)

Government guidance

The government has produced further information on BNG:

• Guidance for developers
• Guidance for land managers
• Guidance for local authorities

Guidance on assessing strategic significance  

Prior to the publication of Greater London’s Local Nature Recovery Strategy, the local planning authority is responsible for specifying alternative documents for assigning strategic significance within the Statutory Biodiversity Metric.

Where the specified alternative documents identify an area as locally ecologically important or identify a habitat as locally ecologically important within a specified location, the strategic significance should be recorded as ‘high’.

In the London Borough of Richmond, these documents will include:

• The Local Plan
• The Richmond Biodiversity Action Plan
• Draft Local Nature Recovery Strategy (when available)

Of particular importance in Richmond is reference to the Richmond Biodiversity Action Plan and the Local Plan.