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Biodiversity Net Gain (BNG)

New planning requirements are coming in that affect major development and in April 2024 will apply to most other development.

Developers will be required to demonstrate that proposals deliver biodiversity net gain (BNG). This is an approach to development that aims to leave the natural environment in a measurably better state than it was beforehand.

The Government has produced the Biodiversity Metric  –  a free biodiversity accounting tool in Microsoft Excel format, which is to be used for the purposes of calculating a 10% gain on the pre-development biodiversity value of the site.  Achieving 10% net gain means fully compensating for losses of habitat on a development site, but then going further so that overall there is a gain in habitat of at least 10% as a result of the development process.

The Government intends to produce guidance on how to use the Biodiversity Metric and achieve net gain during the summer.

1. Will BNG apply to my development?

Under the Environment Act 2021, all planning permissions granted in England (with a few exemptions) will have to deliver at least 10% biodiversity net gain, using the metric developed by DEFRA that generates a biodiversity value for a site before and after development to demonstrate this. This applies to major development from November 2023 and minor development from April 2024. Minor development means:

(i) For residential: where the number of dwellings to be provided is between one and nine inclusive on a site having an area of less than one hectare, or where the number of dwellings to be provided is not known, a site area of less than 0.5 hectares.

(ii) For non-residential: where the floor space to be created is less than 1,000 square metres OR where the site area is less than one hectare.

The following types of development will be exempted from BNG requirements:

  • development impacting habitat of an area below a ‘de minimis’ threshold of 25 metres squared, or 5m for linear habitats such as hedgerows
  • householder applications
  • biodiversity gain sites (where habitats are being enhanced for wildlife)
  • small scale self-build and custom housebuilding

2. How the process will work

The Environment Act 2021 makes all planning permissions (other than exempted ones) subject to a pre-commencement condition requiring the submission of a plan that demonstrates how 10% net gain will be achieved. The management of the habitat created to achieve this must then be secured by legal agreement for a minimum period of 30 years. The habitat creation required to achieve 10% net gain should be undertaken on the development site itself. However if space and circumstances do not allow this provision on a separate site or a mixture of the two would be considered. Offsite habitat creation can be undertaken on land owned by the developer, or on third party land where the landowner is willing to undertake such work and maintain it for at least 30 years in return for a payment from the developer. As a last resort the Government intends to introduce a national credits purchase system for developments unable to meet their BNG requirements locally.

3. Information to be submitted with a planning application

The BNG process is built around the pre-commencement condition, which is when the full details of the metric calculations and of the measures to be taken to secure 10% net gain are required. However, enough information will need to be submitted with the planning application for the Authority to be satisfied that a suitable net gain solution exists for that development.

We are expecting further guidance from Government and secondary legislation (regulations) about the process, but the biodiversity information submitted with the planning application should include the metric calculations and details of the development of habitat creation to achieve net gain. This work  should be undertaken by an experienced Ecologist and will allow the pre-commencement condition to be discharged without delay.

4. BNG does not replace existing legislation and policy

The BNG process simply introduces a quantitative framework for securing and demonstrating net gain. It does not replace the requirement to carry out other assessments of impacts on biodiversity eg. submission of bat survey information. Where there is the potential for impacts on European sites, the Authority will still need to undertake a Habitats Regulations Assessment.

Compliance with a number of other environmental planning policies will still need to be demonstrated by the developer; these include requirements relating to:

  • protected or important nature conservation sites
  • protected or important species
  • irreplaceable habitats

BNG maintains the mitigation hierarchy of avoiding impacts first, then mitigating and only compensating as a last resort. It cannot be used to bypass the mitigation hierarchy.

5. Planning for BNG early in your development planning

The Biodiversity Metric has been designed to disincentivise the loss of better-quality habitats to development, by making them significantly more expensive to provide net gain for compared to lower value habitats.

Consequently, it is important to establish the baseline value of a site at as early a stage as possible when considering its development potential, as the loss of higher value habitats may make a scheme unviable, or may require that parts of the site are safeguarded from development to enable an economically viable scheme to be developed.

6. Clearing sites in advance

Within Schedule 14 of the Environment Act measures have been included that allow the Local Planning Authority to take account of any habitat degradation or destruction undertaken on a site since January 2020, and to take the earlier habitat state as the baseline for the purposes of biodiversity net gain. This is to ensure that there is no advantage to be gained by the deliberate clearance of land in order to achieve a low baseline value for BNG.

If habitats on site have been destroyed or degraded prior to a survey and submission of planning application, the earlier habitat state will be taken as the baseline for the purposes of the biodiversity metric and a habitat condition score of ‘good’ will be allocated to the habitat parcel as a precaution.