Biodiversity net gain (BNG) became mandatory on the 12 Feb 2024 for major developments (residential projects with 10 or more dwellings or sites larger than 0.5 hectares), whilst for smaller developments, BNG requirements began on the 2 April 2024. This includes residential developments with 1-9 dwellings or sites under 0.5 hectares, and commercial projects with less than 1,000 square meters of floor space or sites under 1 hectare.
Back in November 2023 the long-awaited secondary legislation was published in draft format as six statutory instruments – referred to as regulations. The secondary legislation supports the primary legislation (The Environment Act 2021) by setting out specific measures on how BNG is to be delivered, including more detail on information such as the biodiversity gain site register, exemptions, and irreplaceable habitats.
The secondary legislation was one of the last main puzzle pieces that enabled BNG to become mandatory. All six statutory instruments were laid before parliament and approved, prior to BNG becoming mandatory on the 12th February 2024 for major developments.
Alongside the draft secondary legislation, in November 2023, Defra also published a variety of updated tools, resources and guidance which furthered our understanding of how the application of BNG would look now that is has become mandatory. Below, we have summarised some of these updates and have included some key points to be aware of during the BNG process based on our current knowledge and experience.
Statutory Biodiversity Metric
To date, we are familiar with numerous versions of the metric. The updates in November 2023 included publication of the statutory biodiversity metric and associated tools, including a user guide and habitat condition assessment sheets. The user guide (published February 2024) sets out the rules and principles of the metric and guidance on how to complete the metric calculations. This is the only accepted version of the metric for Planning in England now that BNG has become mandatory, and more guidance is due to be released for how to use data from previous metric versions in the statutory metric. Defra has since released guidelines on how to convert data from previous metric versions into the statutory metric.
Biodiversity Gain Hierarchy
This is new terminology to set out the approach to achieving a 10% overall gain. The Biodiversity Gain Hierarchy requires that following consideration of avoiding and/or mitigating impacts to on-site habitats, biodiversity gains are firstly considered through on-site habitat enhancement, followed by on-site habitat creation, then registered off-site gains, and as a last resort, statutory credits may be purchased. This is a key consideration from early in the design stages and adherence to this is to be demonstrated in the Biodiversity Gain Plan.
The Biodiversity Gain Hierarchy differs to the mitigation hierarchy, which is set out in the National Planning Policy Framework (2023) and which should also be followed (and evidenced) during the process of identifying how a net gain will be achieved.
The Biodiversity Gain Plan and planning requirements
A Biodiversity Gain Plan is a document in which a developer demonstrates exactly how a proposed development will achieve the biodiversity gain objective of at least 10%. The plan must include details such as pre-development and post-development habitat information, the completed metric calculation tool, details of habitat maintenance and monitoring and how this will legally be secured (e.g. planning condition, planning obligation, conservation covenant), and whether statutory credits have been purchased. This is considered a pre-commencement planning condition and must be submitted to the local planning authority after planning permission has been granted. The local planning authority will have eight weeks to approve the plan.
Whilst the Biodiversity Gain Plan is a post-permission requirement, it is important to remember that BNG should be considered early in the development process and at all stages to maximise the possible gains the development can deliver.
For development where BNG is required, planning applications must include details of the pre-development biodiversity value as a minimum, including the completed metric calculation tool and a plan of on-site habitats to enable the application to be validated. Local Planning Authorities are likely to require further information to assist in considering BNG for a development and local requirements should be referred to in addition.
Significant/non-significant on-Site enhancements
Defra have now shared definitions of ‘significant’ and ‘non-significant’ enhancements when it comes to enhancing or creating habitats to contribute towards on-site net gain. Significant enhancements, as defined by Defra, require habitat maintenance to be secured legally through either a planning condition, planning obligation or conservation covenant for a minimum of 30 years, similar to off-site gains. Habitat Management and Monitoring Plans are required to demonstrate what practical actions will be taken to ensure successful delivery of significant on-site enhancements (and off-site gains). Non-significant enhancements do not require maintenance to be secured for at least 30 years, unless required for other reasons within local planning policy.
Takeaway thoughts
Although the parliamentary approval of the statutory instruments was confirmed in February 2024, we have already been utilising many of the tools, resources and knowledge which allowed us to be as prepared as possible for the implementation of mandatory BNG. Prior to this, many Local Planning Authorities already required a degree of net gain demonstrated through the use of a metric tool so we are well prepared to continue progressing in this industry now that BNG is mandatory.
As ecologists we are continuously working with developers and landowners to assist with BNG and provide support throughout the process of identifying how a measurable net gain will be delivered. From our experiences so far it is clear that early ecological involvement and stakeholder engagement during a project are vital in securing the best outcomes for biodiversity and meeting the biodiversity gain objective in accordance with good practice principles. Early engagement also allows developers to be aware of potential constraints at an early stage and implement solutions during the design process – where more flexible solutions can be considered and there is increased opportunity to avoid adverse impacts.
More detailed information published by Defra can be found at the links below. If this raises any questions or you would like our support with any BNG projects, feel free to get in touch with us.
