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Biodiversity Net Gain Condition Assessment

Biodiversity net gain (BNG) is a principle in conservation biology that aims for a net increase in biodiversity from a development project. This means that the project should minimise harm to habitats and species as much as possible. It should also enhance the natural environment through actions like creating new habitats, restoring degraded ones, or relocating species.

The goal is to prevent a decline in BNG, and ideally, improve the health and variety of ecosystems. Compliance with BNG standards in development plans may increase the likelihood of gaining planning permission, which is determined by local authorities.

Our team of ecologists and land managers assist clients across England and Wales. They have knowledge of biodiversity net gain requirements, planning policies, and related decisions.

BREEAM assessment

What is a biodiversity net gain condition assessment?

A BNG assessment evaluates the potential impact of a development project on biodiversity and determines if it will result in a net increase or decrease. The assessment involves a thorough survey of the site and surrounding area to identify existing habitats and species. It also includes an analysis of the project’s impact on these elements.

The assessment also includes an evaluation of the proposed measures to mitigate harm and improve BNG. This includes both creating or enhancing habitats or relocating species. Recommendations may be made based on the results to enhance the project design and minimise negative impacts.

The assessment calculates the net gain or loss of BNG based on the difference between the site’s baseline conditions and the expected conditions after completion of the project. Biodiversity net gain condition assessments are often required for development projects to show compliance with planning policies and regulations.

When will BNG become mandatory?

Following the Environment Bill 2020, the Environment Act 2021 was introduced. According to the Environment Act, local planning authorities must ensure that all permissions they grant contribute to a minimum of 10% BNG. The act has provisions for secondary legislation, which will set the effective date for this requirement.

Currently, the implementation of mandatory biodiversity net gain is expected to occur at the end of 2023. There is also a two-year transition period for local authorities to prepare their policies and processes.

The current national policy in England, The National Planning Policy Framework (NPPF)

Paragraph 180 states:

  • “When determining planning applications, local planning authorities should apply the following principles: opportunities to improve biodiversity in and around developments should be integrated as part of their design, especially where this can secure measurable net gains for biodiversity”

Many Local Planning Authorities have already been requesting the assessment for BNG for a number of years already. Many of them are beginning to change local developers’ processes to ensure they meet the set standards as part of the local policy.

What will the Act introduce?

The Environment Act 2021 will require the key points:

  • Developers must deliver BNG at a minimum of 10% through their schemes. This will be measured through a metric, currently Biodiversity Metric 3.1. This tool can help to identify your biodiversity unit score and translate it into the standards of local planning authorities.
  • A developer will need to demonstrate how BNG will be delivered on developed land. This will be demonstrated through the production of detailed Landscape Planting Schemes. Landscape Management Plans and Monitoring assessments for on and/or off-site can also be used.
  • A mitigation hierarchy is to be followed and demonstrated to avoid, minimise or compensate. If it is not possible to compensate on the development site, then offsetting on other designated sites will be required elsewhere.
  • Developers will have to guarantee that BNG is maintained for at least 30 years (as outlined in Landscape Management Plans).
  • New “local nature recovery strategies” will be prepared to cover England by “responsible authorities”. This will encourage habitat creation and enhancement in the right places.
  • Conservation covenants will be a mechanism used to deliver this (this approach is in preparation by Defra and Natural England).
  • A national register of land used for BNG will be established. This will involve setting up a new BNG credits market.
  • Biodiversity metric calculates are only concerned with habitat parcels and do not take protected species into consideration.
  • Other ecological legislation and policies still apply.

How Can Collington Winter Assist?

If you require more information regarding a biodiversity net gain condition assessment, then our team at Collington Winter will be more than capable to assist you. Achieving BNG through development is something that we are qualified and experienced in. Plus, we can offer advice on both large and small sites.

Please get in touch if you would like further information about BNG, or net gain condition assessments. You can email our Ecology Director at or use the form below and a member of our team will be in touch with you.

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