Biodiversity Net Gain
Biodiversity Net Gain Update for Agents and Developers
You may be aware of 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. Biodiversity net gain is now mandatory for certain types of development under the Environment Act 2021.
The Biodiversity Metric is a way of quantifying this. Natural England has published a free biodiversity accounting tool in Microsoft Excel format, which is to be used for the purposes of calculating biodiversity net gain – see Statutory biodiversity metric tools and guides – GOV.UK for more guidance from the Government.
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 has introduced this requirement to help meet its aspiration to leave the environment in a better state than it found it, and to help meet targets for nature recovery required under the Environment Act. Since 01 January 2023, all public authorities have been under a statutory duty to conserve and enhance biodiversity. The main areas of the National Park’s work that help to deliver the Authority’s biodiversity duty are set out in Table 1 of the Authority’s Biodiversity Duty Reporting Update (December 2023). In terms of planning policy, in addition to the NPPF’s requirement for net gain in biodiversity (paragraph 180), Policy SP6 in the adopted Local Plan requires proposals to protect, maintain and enhance features of the natural environment, including habitats and species of biodiversity importance.
1. BNG has been mandatory for major and minor developments since Spring 2024
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 a 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 February 2024 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 are exempted from BNG requirements:
- Householder development as defined within article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015. This includes small projects such as home extensions, conservatories or loft conversions.
- Development granted planning permission by a development order under section 59. This includes permitted development rights.
- Development subject to the de minimis exemption – development that does not impact a priority habitat and impacts less than 25 square metres (e.g. 5m by 5m) of habitat, or 5 metres of linear habitats such as hedgerows.
- Self-build and custom build development – development which:
- consists of no more than nine dwellings, and
- is carried out on a site which has an area no larger than 0.5 hectares, and
- consists exclusively of dwellings which are self-build or custom housebuilding as defined in section 1(A1) of the Self-build and Custom Housebuilding Act 2015.
- Urgent Crown development granted under s293A TCPA 1990.
- Development of a biodiversity gain site – development which is undertaken solely or mainly for the purpose of fulfilling, in whole or in part, the biodiversity gain planning condition which applies in relation to another development.
- Development related to the high speed railway transport network – development forming part of, or ancillary to, the high speed railway transport network comprising connections between all or any of the places or parts of the transport network specified in section 1(2) of the High Speed Rail (Preparation) Act 2013
2. How the process will work
The Environment Act amends the Town and Country Planning Act to make 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.
To view information regarding the monitoring fees, please refer to the last item AM 698/24 in the ‘List’ section on the following web page:
The habitat creation required to achieve 10% net gain can be undertaken on the development site itself if space and circumstances allow, on a separate site or a mixture of the two. 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 – see below. As a last resort the Government has introduced a national credits purchase system for developments unable to meet their BNG requirements locally.
Offsite Biodiversity Units for development in the New Forest National Park
The national system for Biodiversity Net Gain incentivises the delivery of any off-site biodiversity units within the vicinity of the development site. The National Park Authority has an overarching legal agreement in place with the landowner and our neighbouring planning authority of New Forest District Council that enables development in the National Park area to access biodiversity units at Keyhaven near Lymington. Further details of this approved biodiversity scheme are available at Keyhaven Natural Capital — Kingwell.
3. Information to be submitted with a planning application
The BNG process is built around a 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 be required at determination stage for the LPA to be satisfied that a suitable net gain solution exists for that development.
The most straightforward option is to submit all required information with the planning application whenever possible, so that discharge of the BNG condition can follow on immediately after determination. The metric calculations and associated reporting as well as the development of habitat creation to achieve net gain will need to be undertaken by an experienced Ecologist.
Where the required gain in biodiversity is being delivered on the development site itself, a legal agreement is required to ensure the habitat is provided and maintained for at least 30 years as required by the Environment Act 2021. To assist in this, we have prepared the following template legal agreements for applicants:
