Biodiversity Net Gain

Biodiversity is the variety of all living things including species, habitats and ecosystems.

Biodiversity net gain (BNG) is an approach to planning and land management that leaves the natural environment in a better state than it was before. BNG will deliver measurable improvements for biodiversity by enhancing or creating new habitats in association with development.

We are committed to protecting, conserving and enhancing our natural environment and BNG will help to deliver the objective set out in the Sustainable Economy Strategy to improve, manage and promote biodiversity and nature recovery.

We are currently considering how best to implement BNG and we will be publishing guidance to help guide you through the process.

Government guidance on biodiversity net gain can be found on the GOV.UK website.

Why is BNG important?

There has been and continues to be a significant decline in biodiversity in the UK. This is despite legislation and policy to protect biodiversity and wildlife. Whilst designated nature conservation sites and priority habitats are of significant value, the overall ecological network of habitats and species is important for biodiversity and nature recovery.

Measures to benefit nature including BNG can also have positive effects on other priorities and goals. For example, BNG will contribute to access to greenspace, place-making and improvements to air quality which are all important for health and wellbeing. It will also help to increase resilience to the effects of climate change.

The requirement for BNG does not alter the existing legal requirements and protections for the natural environment such as protecting important habitats and species.

When will BNG become mandatory?

From 12 February 2024, all major planning permissions granted in England will have to deliver a minimum of 10% BNG under the Environment Act 2021. BNG will be mandatory for small sites from 2 April 2024. Certain developments are exempt from BNG.

You will need to submit information on BNG with the planning application and, if granted planning permission, a Biodiversity Gain Plan showing how BNG will be achieved must be approved by us prior to commencement of development.

The National Planning Policy Framework  (paragraphs 180, 185 and 186) refers to net gains for biodiversity as do the site allocation policies in the Site Allocations DPD. (12MB PDF)  Adopted District Plan Policy DP38: Biodiversity (18MB PDF)  also refers to ensuring development contributes and takes opportunities to improve, enhance, manage and restore biodiversity and green infrastructure, so that there is a net gain in biodiversity.

How is BNG calculated and assessed?

BNG is calculated using the approved Biodiversity Metric which measures the biodiversity value of habitats in ‘biodiversity units’ as a proxy for nature. The Biodiversity Metric is used to assess how a development might change the biodiversity value of a site. It can help to inform the design, layout and management of a site to support biodiversity.

The application of BNG will require ecological expertise to interpret the inputs and outputs of the Biodiversity Metric.

How is BNG delivered?

Biodiversity net gain can be delivered on-site, off-site or through a combination of on-site and off‑site measures, however, the implementation of BNG should align with the local objectives and priorities for biodiversity improvements and nature recovery. Off-site BNG should also ideally be located in Mid Sussex District as close to the development site as possible so that local communities benefit from enhanced biodiversity.

BNG should be meaningful; it should deliver demonstrable benefits for biodiversity both in the planning application process and in its ongoing implementation.

Appropriate funding, management and contingency arrangements will need to be in place to look after BNG for a minimum of 30 years.

BNG will be monitored by the Council and enforced if necessary. Failure to comply with the general biodiversity gain condition by commencing development without approval of the Biodiversity Gain Plan will be a breach of planning control. The initial delivery and ongoing management of BNG will also be monitored and enforced if necessary.

The Council will charge monitoring fees through a section 106 planning obligation to cover the cost of monitoring and reporting duties over the 30 years. Legal fees will also be levied.

What is the approach to BNG?

It is preferable to have a strategic approach for BNG so that BNG can be considered alongside wider priorities such as nature recovery, landscape, green infrastructure and resilience to the effects of climate change.

The mitigation hierarchy embedded in national policy should be followed and applied. This is where the impact on biodiversity should first be avoided, then minimised, then compensated as a last resort.

Higher levels of BNG (more than the minimum 10%) will be encouraged and developments should seek to maximise opportunities to deliver meaningful BNG.

Off-site biodiversity net gain for land managers

Identifying land for off-site biodiversity net gain provides an opportunity to enhance your land for nature and may be an income stream to help manage the land for biodiversity.

Land will need to be registered as a biodiversity gain site using the Government’s online service

Land provided for off-site biodiversity net gain will need to be legally secured for this purpose for a minimum of 30 years.

A planning obligation (by way of a section 106 legal agreement) with the local planning authority or a conservation covenant with a responsible body will need to be used to secure the land.

An ecologist will need to calculate how many biodiversity units are available for the site and you will need to decide a price for each biodiversity unit.

The Council is keen that off-site biodiversity net gain sites contribute to the wider biodiversity, habitat and nature recovery priorities so you are encouraged to talk to us about your plans.

Further information can be found on the GOV.UK website.

Wildlife and Planning

For information about the requirements for great crested newts, please see the Wildlife and Planning page.

For information about the requirements for planning applications within 7km of Ashdown Forest, please see the Protecting Ashdown Forest page.

Other biodiversity enhancements can also be important. Measures to help wildlife in your garden or development include:

  • Bird boxes and roosts
  • Bat boxes
  • Swift bricks
  • Bee bricks
  • Insect hotels/ bug hotels
  • Hedgehog highways
  • Native wildflower planting with nectar- and pollen-rich flowers
  • Rain gardens
  • Adding water including a pond if you have space
  • Keeping existing trees, hedgerows and streams
  • Creating wildlife corridors and providing links to other areas of green space
  • Lighting designed to avoid disturbing and harming wildlife

Contact us

To discuss any off-site BNG requirements for planning applications or to discuss off-site BNG proposals, contact:  

Last updated: 16 February 2024