Biodiversity Net Gain

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Legal Requirement

Under the Environment Act 2021, it is mandatory for developments (excluding exemptions) to deliver a minimum of 10% biodiversity net gain. 

The biodiversity net gain requirement may be higher for some districts and local authorities so it is important to check local planning policy.

Biodiversity enhancement is also required under the National Planning Policy Framework (2021).

Exemptions

The following types of development may be exempt from biodiversity net gain rules (though biodiversity enhancements may still be required under the National Planning Policy Framework):

• Existing planning applications (if submitted prior to 12 February 2024 for major developments or 2 April 2024 for minor developments).
• Variations of planning permission.
• Developments below the threshold (developments that do not impact a priority habitat and impacts less than 25m2 of onsite habitat and less than 5m of onsite linear habitats such as hedgerows).
• Householder applications.
• Self-build and custom build applications (developments that are a maximum of 9 dwellings on a site no more than 0.5 hectares).
• Biodiversity net gain sites.
• High speed rail transport network.
• Urgent crown developments.
• Developments that are granted planning permission by a development order (including permitted development rights).

Understanding Biodiversity Net Gain

Biodiversity net gain requires developments to ensure that habitats for wildlife are left in a measurably better state than they were before the development.

Measuring Biodiversity Net Gain

For the purposes of biodiversity net gain, biodiversity value is measured in standardised biodiversity units. Biodiversity units can be lost through development or generated through work to create and enhance habitats. 

Biodiversity value is calculated using the statutory biodiversity metric by measuring how many biodiversity units are present on a site before development and how many biodiversity units are needed to replace the units of habitats lost and to achieve 10% biodiversity net gain. Areas of habitat, hedgerows and watercourses are subject to separate calculations.

Ways to Deliver Biodiversity Net Gain

Through site selection and layout, developers should avoid or reduce any negative impact on biodiversity. There are three ways a developer can achieve biodiversity net gain but these steps must be followed in order: 

1. They can create biodiversity on-site (within the red line boundary of a development site). 
2. If developers cannot achieve all of their biodiversity net gain requirements on-site, they can deliver through a mixture of on-site and off-site. Developers can either make off-site biodiversity gains on their own land outside the development site (which will need to be included on the Biodiversity Net Gain Register), or buy off-site biodiversity units on the market.
3. If developers cannot achieve on-site or off-site biodiversity net gain, they must buy statutory biodiversity credits from the government. This should be a last resort. The government will use the revenue to invest in habitat creation in England. 

The land owner is legally responsible for creating or enhancing habitat, and managing that habitat for at least 30 years to achieve the target condition. This applies if you make on-site gains or sell off-site gains on a site you own. If you buy off-site units, you are paying the land manager to manage the land for 30 years to achieve the target condition.

Good Practice Principles for Achieving Biodiversity Net Gain

These ten principles set out good practice for achieving biodiversity net gain and must be applied all together, as one approach.

1. Apply the mitigation hierarchy. Avoid then minimise impacts on biodiversity. As a last resort compensate for losses onsite or, if not possible, offset offsite.
2. Avoid losing biodiversity that cannot be offset by gains elsewhere. This means avoiding impacts to irreplaceable habitats which include ancient woodland, ancient and veteran trees, blanket bog, limestone pavements, coastal sand dunes, spartina saltmarsh swards, Mediterranean saltmarsh scrub and lowland fens.
3. Be inclusive and equitable. Engage with stakeholders during design, implementation and monitoring of biodiversity net gain.
4. Address risks. Mitigate for any uncertainty or risk to delivering biodiversity net gain and add contingencies.
5. Make a measurable net gain contribution.
6. Achieve the best outcomes for biodiversity. Use an evidence-based approach to biodiversity net gain design, implementation and monitoring.
7. Be additional. Achieve nature conservation outcomes that exceed existing obligations.
8. Create a net gain legacy. Ensure net gain generates long term benefits.
9. Optimise sustainability.
10. Be transparent.

Biodiversity Net Gain Strategy

Biodiversity net gain must be considered early in a project and in collaboration with the rest of the project design team which may include a landscape architect. 

A biodiversity net gain strategy should include (but may not be limited to) the following documentation:

• Baseline ecology survey report including a habitat plan and habitat condition assessments.
• Landscaping proposals showing habitats to be retained, created and enhanced/restored, where applicable.
• A completed version of the statutory biodiversity metric.
• A completed version of the biodiversity gain plan template.
• A 30-year habitat management and monitoring plan.