Need a biodiversity net gain plan?

Everything You Need to Know About Biodiversity Net Gain and the Planning System

Biodiversity net gain (BNG) became a mandatory requirement for new development projects in England on 12 February 2024. The new rules came into force following a two-year transition period (intended to end in November 2023) designed to give local authorities time to adjust to the legislation. The UK government introduced a separate statutory biodiversity metric for assessing small sites on 2 April 2024.

Mandatory bng means that new developments must leave the natural environment in a measurably better state following completion than before. A minimum 10% uplift in biodiversity must be achieved and the site must be maintained for 30 years. This can be achieved through habitat improvement, restoration and creation.

To achieve planning permission, a biodiversity net gain plan must be submitted to the local planning authority. The plan must demonstrate how the site will achieve biodiversity net gain bng and the local authority must approve it.

BNG in practice

BNG now forms a key part of the planning process in England. Whether a proposal is for a major development, minor development, or falls under revealed/permitted development, developers must demonstrate how their scheme will achieve BNG at the planning application stage. This is typically set out using a robust biodiversity gain plan template, aligned with developer guidance and the expectations of the relevant local planning authority.

An ecological consultant will carry out a desktop survey to establish valuable habitats present or near to the proposed site’s red line boundary, followed by a site visit. A record will be made of all ecological features, wildlife species and habitats on the site, along with habitat quality and condition, to achieve a pre development biodiversity value.

BNG assessments are underpinned by a biodiversity metric tool calculation, using either the small sites metric or the latest version of the statutory Defra metric, depending on the identified scale and nature of the proposal. The relative biodiversity value pre development will be compared against post development plans to determine whether the 10% biodiversity gain objective has been met.

This process accounts for important habitats, existing protections, and any statutory protected sites, including irreplaceable habitats, where BNG requirements may vary depending on site constraints.

The ecological consultant will then assess the optimal way to create measurable improvements and deliver biodiversity net gain on the site following development, by comparing the two figures and adhering to the mitigation hierarchy and devising an overall biodiversity gain plan.

Where possible, biodiversity gain should be achieved on site through well-designed on site habitat creation and habitat enhancement, such as species-rich grassland, woodland planting, wetlands, and green infrastructure.

These biodiversity enhancements are designed to support rural communities, reduce adverse impacts associated with development, especially habitat degradation and enhance biodiversity. On site delivery is often preferred by planning authorities, particularly where developments are proposed on a developer’s own land and can be secured through planning conditions or a biodiversity gain condition.

For phased developments or sites with limited space, some or all of the required gain may need to be delivered away from the site. This can include off site BNG through the purchase of off site biodiversity units or delivery on off site habitats secured via a compensation plan. Off-site solutions must still meet statutory requirements, align with planning approval and demonstrate that the development meets BNG targets over the required time period.

Further surveys

Following the BNG assessment, further surveys may be required before a biodiversity net gain plan can be completed. These may include protected species surveys, additional ecology surveys, an ecological impact assessment or a Habitat Management and Monitoring Plan (HMMP) to scrutinise biodiversity improvement schemes.

The BNG market

While delivery of on site gains is the preferred option, if this is not achievable,bio diversity gains away from the site will need to be identified. Options for this include buying biodiversity units off site from a habitat bank, local landowners or the national register, or as a final resort, buying off site credits from sources approved by government, which go towards funding future nature conservation schemes.

The BNG plan: comply with National Planning Policy

The plan will propose solutions for complying with biodiversity net gain regulations. Proposals may include avoiding damaging biodiversity on a site and opportunities for improving existing wildlife and habitat creation. This will give a local planning authority full details of how mandatory biodiversity net gain legislation will be adhered to by a developer.

The BNG plan will provide details of how net gain will be delivered to ensure that the environment will be left in a measurably better state. By referring to the biodiversity gain hierarchy, the consultant will calculate the best way to plan for habitat loss. If there are ways of restoring or enhancing on site habitats, or new habitat can be created to fulfil the BNG requirement, these are the best options.

If options for significant on site gains are limited, off site units or statutory biodiversity credits will be required as a last resort option. The BNG plan will clarify off site solutions: there may be options to purchase units from local land owners or land managers operating habitat banks, or to buy statutory credits from a public body. A Biodiversity Gain sites register provides information about suitable sites.

Legally secured agreement

The purchase of off site biodiversity units requires a legal agreement between the developer and landowner, called a conservation covenant. Details of the conservation covenant will form part of the biodiversity net gain bng plan, and it will confirm that the enhanced habitats will be maintained for at least 30 years to ensure that the biodiversity gain requirement is achieved. Schemes must be overseen by a responsible body to monitor their environmental benefits.

The BNG Report

The report will give details of the methods of securing BNG, the biodiversity currently on site, the biodiversity metric used and plans of the site.

While the BNG plan establishes the method for making on site or off site changes, the BNG report will provide evidence of key data such as the pre-development and post-development biodiversity values, details of the site and the project. It considers matters such as Sites of Special Scientific Interest, Nationally Significant Infrastructure Projects and marine net gain as part of a marine development.

The report may also note relevant information such as Local Nature Recovery Strategies, guidelines from Natural England, Wildlife Trusts, local planning policy or the Environment Act, which introduced mandatory bng.

Further BNG requirements

Before BNG can be implemented, a local planning authority might request further surveys or assessment before it is satisfied that a developer has fulfilled all their responsibilities. These can include specific species surveys such as air pollution surveys or ancient woodland surveys.

Assessments that could be carried out alongside a BNG assessment include air quality assessments, noise assessments and river condition assessments. A BNG Plan detailing ongoing habitat and land management to demonstrate that the required level of BNG is adhered to might also be requested.

Biodiversity Gain Plan

This Defra-created document enables developers to summarise how they will fulfil BNG requirements. Some local planning authorities may require a Biodiversity Gain Plan; if so, ecological expertise will be needed to provide guidance.

Habitat Management and Monitoring Plan

To ensure that a BNG site makes the necessary amount of progress over the required 30-year term, developers might put a HMMP in place.

BNG Guidance: Final Points

Biodiversity net gain legislation applies to major applications, multiple developments, householder applications, custom build applications and home extensions.

If you have a development project and need further information about how to comply with planning obligations when it comes to biodiversity net gain, consult a suitably qualified ecological consultant.

The consultancy you engage must be able to manage all key components of BNG, from baseline surveys and metric calculations to long-term management and habitat restoration. They can also advise if you need to buy statutory biodiversity credits as a last resort option.

Consultants will be able to provide further detail where required by planning officers and inform planning conditions, ensuring proposals progress smoothly through the planning application process to seeing planning permission granted.

By combining technical expertise with practical solutions, the right consultancy will help developers navigate complex planning requirements, reduce risk, and deliver meaningful biodiversity gains that stand up to scrutiny.