1. Biodiversity Net Gain in the Planning Process
What is Biodiversity Net Gain?
Biodiversity Net Gain is an approach to planning and land management that ensures development will have a positive impact on biodiversity. This new planning requirement came into force in England in 2024. The principle of BNG requires developments to provide or enhance habitats for wildlife such that the environment is left in a measurably better state than it was prior to the development taking place.
Biodiversity Net Gain will transform how developments are planned, designed, built and maintained. It has the potential to bring benefits to both people and wildlife such as providing communities with beautiful natural green spaces and bringing back wildlife. It also has potential for improved air quality, flood management and soil stability.
BNG was introduced by Schedule 7A of the Town and Country Planning Act 1990, inserted by the Environment Act 2021. This is referred to as biodiversity net gain in Planning Practice Guidance to distinguish it from other or more general biodiversity gains.
East Devon District Council Requirements
Our guidance is strongly underpinned by Biodiversity Net Gain Good Practice Principles for Development (Construction Industry Research and Information, 2016). These principles provide an industry standard framework to ensure that Biodiversity Net Gain is much more than a box ticking exercise or a way of achieving biodiversity-by-numbers.
Currently, we are seeking a minimum 10% Biodiversity Net Gain (i.e. 110% of pre-development biodiversity value) through use of the Statutory Defra Biodiversity Metric or the Small Site Metric; the net gain must be meaningful as well as measurable. From the earliest stage, proposals for new development should involve competent and experienced ecologists contributing to the various design and layout options to enable the minimum 10% Biodiversity Net Gain to be delivered on site. Where this is clearly demonstrated not to be feasible (to be agreed with the Local Planning Authority) it may involve offsite compensation.
To ensure the requirements for Biodiversity Net Gain are achieved, it is important that these issues are addressed at a very early stage in the application process. Consequently, applicants are encouraged to engage in the Council’s Pre-application Advice Service.
Even where planning application sites are exempt from the national mandatory 10% BNG requirement, EDDC still expects applicants to achieve a net gain and other biodiversity enhancements, in line with the National Planning Policy Framework (2024) and relevant local plan policy.
BNG and existing wildlife legislation and policy
BNG is additional to, and does not replace, existing wildlife legislation, policy, and guidance, e.g., Environmental Impact Assessment (EIA), Habitats Regulation Assessment (HRA) etc. Therefore, development proposals will still be subject to the same biodiversity assessment criteria for protected or important nature conservation sites and irreplaceable habitats.
Biodiversity Net Gain only relates to habitats so does not take rare, notable, and protected species into consideration. It will therefore be necessary to demonstrate how these species have been considered, protected, and supported through the Ecological Impact Assessment (EcIA) process to address legal requirements and to meet Policy EN5 (Wildlife Habitats and Features) of the Adopted East Devon Local Plan.
The presence of protected species is expected to influence the design, layout and specification of the proposals for habitat retention, enhancement and creation and this should be clearly demonstrated in the planning application documentation.
Biodiversity Net Gain in the Planning Process
Most planning applications, with a few exemptions, will be required to demonstrate a minimum 10% Biodiversity Net Gain under the Environment Act 2021.
BNG should be considered early in the planning process to ensure it is factored into site selection and design, as well as considering botanical and protected species survey windows which are seasonally dependent. Applicants are encouraged to use the Council’s Pre-application Advice Service to further understand the specific requirements in relation to their site.
BNG is a mandatory requirement, and has had a phased introduction as follows:
Major development: 12 February 2024
Small-scale development: 2 April 2024
Nationally Significant Infrastructure Projects: November 2026
Developers must assess the pre- and post-development habitat value of their proposals to establish that a minimum 10% gain can be achieved prior to submitting a planning application. The 10% gain is required in legislation and therefore there is no scope for LPAs to allow a reduction on viability grounds.
GOV.UK biodiversity net gain planning practice guidance sets out the framework of how BNG will be applied in the planning process. The Devon County Council website also provides guidance for applications made in Devon and should be followed, unless stated otherwise.
Exemptions
Following consultation in May/June of 2025 on improving the implementation of biodiversity net gain for minor, medium, and brownfield development, several amendments to the type of developments that are exempt from mandatory BNG have been announced on 14 July 2026 and will take effect from Thursday 6 August, 2026. BNG rules do not apply to the following types of development.
Planning applications submitted before mandatory BNG
Any planning applications for developments made before 12 February 2024 are exempt from BNG. For small (minor) developments, any applications made before 2 April 2024 are exempt.
Householder applications
Small projects householders carry out in their own homes to include: home extensions, conservatories, loft conversions.
Variations of planning permission
Transitional arrangements apply for variations to existing planning permissions. For example, where the original planning permission was not in scope of BNG, BNG will not apply to future variations in most cases.
Developments of 0.2 hectares or below
From 6 August 2026, BNG does not apply to planning applications for developments where the site area within the red line boundary is 0.2 hectares or below.
This exemption does not apply if onsite priority habitat is negatively impacted*.
* A development ‘impacts’ a habitat if it decreases its biodiversity value.
Development subject to the ‘de minimis’ rule
Development that impacts* less than 25 square metres (5m x 5m) of onsite area habitat or less than 5 metres of linear habitat (such as hedgerows, line of trees, or watercourses) within the red line boundary.
This exemption does not apply if onsite priority habitat is negatively impacted.
* A development ‘impacts’ a habitat if it decreases its biodiversity value.
Temporary developments
From 6 August 2026, BNG does not apply to short-term developments if the whole development is temporary and planning permission is granted for 5 years or less.
This exemption does not apply if onsite priority habitat is negatively impacted.
Self-build and custom build applications
From the 6 August 2026, the self-build and custom build exemption will no longer apply for new planning applications.
Your self-build or custom build application is exempt from BNG if you apply for planning permission before 6 August 2026 or apply for a variation of planning permission on or after 6 August 2026 and the original planning permission was exempt.
Sites created for off-site BNG gains
Developments creating or enhancing habitats solely or mainly for the purpose of fulfilling the BNG planning condition for another development, are exempt.
These sites must be registered on the Gain Site Register to qualify for this exemption.
Other Exemptions
The following are exempt by the Environment Act 2021:
Urgent crown developments
Developments that are granted permission by a development order (including permitted development rights)