Biodiversity net gain

Biodiversity is the variety of all living things on our planet, from 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.

We are committed to protecting and conserving the natural environment, and BNG is at the forefront of our planning system so that habitats within Buckinghamshire can be protected for years to come.

Biodiversity net gain is important because:

• the natural environment provides benefits to us all, and is essential for the processes that support life on this planet
• many habitats are lost or degraded by development, and there are limited measures in place to value, maintain, enhance and create wildlife habitats
• it delivers measurable improvements for biodiversity by enhancing or creating new habitats in association with development

You can read further information on the importance of biodiversity on the Royal Society website and the Convention on Biological Diversity website.

You can also read the biodiversity net gain brochure on the Natural England website for an overview of BNG and its benefits.

BNG is calculated using a biodiversity metric, which measures the biodiversity value of habitats in ‘biodiversity units’ as a proxy for nature.

The metric can be used to calculate how a development might change the biodiversity value of a site. It can help you to design, plan and make land management decisions that better support biodiversity.

It uses changes in the extent, distinctiveness and condition and habitats, and compares the biodiversity value of habitats found on a site before and after development to determine if there is a loss or gain in biodiversity.

There are 4 key factors that underpin this comparison:

• habitat size
• condition
• distinctiveness
• location

See the guidance about using the biodiversity metric on GOV.UK.

You can also download the latest version of the biodiversity metric and guidance from Natural England.

All of our local plans have policies that require that biodiversity net gain is achieved. View more about the requirements in our Biodiversity Net Gain Supplementary Planning Document.

The requirement has risen from 'any increase' to 10% BNG in the latest legislation.

This applies to most major applications (with some exceptions) and will apply to applications made for ‘small sites’ from 2 April 2024, until which time, local policy continues to apply.

View updates and guidance on the national proposals for BNG on the GOV.UK website and the DEFRA blog:

• BNG on GOV.UK
• BNG on the DEFRA blog

The requirement for biodiversity net gain doesn’t alter existing requirements and protections for the natural environment such as protecting important habitats and species. These must be achieved alongside providing BNG.

We have released interim guidance on the technical topics strategic significance and spatial risk.

These form part of the government's biodiversity metric. This guidance is aimed at the ecological advisors of both planning applicants and landowners wanting to choose sites for biodiversity net gain delivery.

The guidance will be superseded with the finalised Local Nature Recovery Strategy for Buckinghamshire and Milton Keynes.

View the Interim Strategic Significance & Spatial Risk Guidance (PDF, 1.53 MB)

Gains in biodiversity should be achieved on-site (within the proposed development site) and this should be a key consideration when designing development proposals.

This falls in line with the principle of the mitigation hierarchy that is embedded in national planning policy, where the impact on biodiversity must first be:

• avoided, then
• minimised, then
• compensated for on-site

Only as a last resort, and if compensating for losses on-site is not possible, then biodiversity losses should be offset by gains off-site.

Where a development is set to lose biodiversity value because of proposed work, conservation work can be done on the site to try and compensate for the losses. This is as well as any planned measures to avoid or mitigate biodiversity loss.

Compensating for the biodiversity loss by improving biodiversity elsewhere should be used as a last resort. In certain cases, it is not appropriate and should not be used.

Developments must:

• have applied the mitigation hierarchy
• follow national government BNG principles and rules including being as local to the site of impact as possible

The habitat should also be located somewhere of strategic significance to ecology, for example where they help wildlife to move through the landscape by providing a connective corridor or buffering an existing wildlife site.

Currently, applicants in Buckinghamshire have the option to offset their biodiversity losses within their own landholdings or through a third party (such as a Habitat Bank). The management of offset sites must be legally secured for a minimum of 30 years.

We’re unable to recommend third-party offset providers and at this stage a national or local list of such providers is not available. However, you may want to approach BNG brokers, Habitat Banks, local landowners, land managers or nature conservation trusts to help you achieve your biodiversity net gain requirements.

We will be offering a Habitat Bank Regulation Service.

Once we have legal agreement in place with Habitat Banks we will list them on the website as potential providers of biodiversity units. However, it's an open market and other options may be available.

Register your interest in a legal agreement to regulate an offsite biodiversity net gain site.

You can contact us if you are a provider of biodiversity offsets or would like more information on the options available at

We have a legal agreement for the following sites, meaning they can sell biodiversity units to developers, and we will act as the regulator to ensure that the proposed biodiversity gains are achieved.

Other sites may be available on the open market, regulated by third parties.

Email: [email protected]