What is Biodiversity Net Gain?

29 Mar 2023 | BY Apex Ecology

Biodiversity net gain is one of the most significant changes regarding wildlife in planning law in England in the last 30 years. BNG is set to create a new market for biodiversity ‘units’.

This means that measuring and securing BNG requires expert ecological knowledge. Firstly to assess the habitats on site, and then to measure the baseline biodiversity value. All before assessing how the required 10% uplift over baseline value can be achieved and delivered.


What is the purpose of Biodiversity Net Gain? 


The new BNG approach to development is targeted to leave the natural environment in a measurably better state than it was previously. To halt and reverse the national decline in biodiversity, and support the delivery of better quality, better connected ecological networks.


How is BNG measured?


To demonstrate a biodiversity net gain, the baseline biodiversity value is calculated via a metric. The designs of the proposed development are also assessed with the metric and the post-development score for biodiversity value is compared to that of the baseline value.


The Law and BNG


Biodiversity net gain is not a mandatory requirement yet. But this will change in November 2023 when the Environment Act 2021 becomes a part of the planning application system via the amended Town and Country Planning Act 1990.


The 10% Increase in Biodiversity Value 


For some development projects landscape design that has already been drawn up may need amending to increase the uplift to reach the 10% increase in biodiversity value. However, not all developments will be able to achieve an onsite 10% uplift over the baseline. Where the required uplift cannot be achieved onsite, the uplift can be provided elsewhere. As yet, little is known as to where this offsite uplift can be located. It is assumed that secondary legislation for biodiversity net gain (to be published) may well require any offsite uplift to be provided within the same planning authority as the proposed development.

In the instances when the required 10% uplift cannot be achieved either on or offsite then there is to be an option to purchase ‘biodiversity credits’ via a government scheme. The biodiversity credit scheme is at present assumed to be a short-term measure until local schemes of ‘habitat banking’ are available via local planning authority schemes.

All sites where the 10% uplift in BNG is achieved will be registered to keep records of each site. Prior to the commencement of the development, all BNG plans will need to be approved by the local planning authority. The biodiversity net gain plan for registered sites will be subject to a minimum 30-year timeline.


Biodiversity Net Gain services from Apex Ecology


A high level of liaison with clients and architects/landscape architects is likely to be a part of all but the smallest of biodiversity net gain assessments. Ecologists are best contacted at the earliest possible stage to allow plans to be drawn up with biodiversity net gain considered preferably at the outset of the design stage.

Apex Ecology are experienced in BNG assessments and reporting and we are constantly updating our knowledge base and experience. Our experience covers a broad ecological base that can help in mitigating and compensating for losses so as to achieve the post-development target value.

Recent training includes workshops on the legalities of how the planning system will change when biodiversity net gain becomes mandatory in November 2023 and a River Condition Assessment (RCA) course. River Condition Assessment uses condition indicators from a Modular River Physical (MoRPh) assessment. Where rivers (or canals, etc.) are within, or fall sufficiently close enough to the redline boundary of a planning application site, the findings of the River Condition Assessment feed directly into the metric for the BNG assessment.

Apex Ecology has been involved in biodiversity net gain projects of various sizes and we have comprehensive knowledge of utilizing the Small Sites Metric (SSM is generally used for sites under 0.5Ha) and the full metric currently at version 4.0.


Contact Us


Biodiversity net gain will shortly become a mandatory part of planning applications in England.

To discuss your needs to meet required targets then please contact us at 01782 346494, email us at [email protected], or fill out our contact form.