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How will Biodiversity Net Gain affect new developments?

Sep 21, 2022

By Laura Potts MRTPI, Planning Consultant, CAD Planning

Biodiversity Net Gain (BNG) is the principle that all future development and infrastructure projects must leave the site ‘measurably’ better for biodiversity than before. It will come into force in 2023 and marks a significant change for developers.

The minimum statutory improvement under the 2021 Environment Act is an additional 10% above a site’s existing baseline, meaning that 110% BNG must finally be achieved, whether on a brownfield or greenfield site. This is a noble aim and one that has been largely welcomed in principle by the industry.

BNG forms part of the Government’s 25-year environmental improvement plan and originated in a 2018 consultation that showed industry support for greater biodiversity protection. This was followed up in Spring and Summer 2019, in a series of statements confirming it would be mandatory for all new development in England to show biodiversity net gain in order to be granted planning permission. This requirement was put on a statutory footing in the Environment Act 2021, albeit with a delayed ‘in force’ date of November 2023.

However, many councils are already expecting applications to demonstrate some improvement on this front, and as we get closer to the introduction of the new rules, it is expected more will follow. In fact, some local planning authorities are already raising the bar to 20% increased biodiversity because of the severity of the climate crisis. Currently, Cornwall Council require 10% BNG on major applications only.

But how will the 10% biodiversity gain be measured?

The government is currently running a technical consultation on the DEFRA Biodiversity Net Gain Metric that will become statutory in England in 2023. This is the biodiversity accounting tool developers use to calculate biodiversity gain. The BNG tool measures nature losses and gains, using a set range of ecological criteria.

Closing on 27th September 2022, the consultation will gather feedback on the Biodiversity Metric 3.1 and the Small Sites Metric. The consultation, which is a requirement of the Environment Act 2021, will inform the production of a statutory metric later in 2022, a year ahead of biodiversity net gain becoming mandatory in England.

The gain is to be secured for at least 30 years through a biodiversity net gain plan and can be delivered onsite, offsite through a registered gain site or, as a last resort, through the purchase of credits.

Inevitably, not all sites can achieve their 110% net gain, and some will be permitted to pay to offset their obligations to other registered sites. Ambition to keep funds local has motivated nature organisations and local authorities to map their existing regional Green and Blue Infrastructure networks (e.g. woodland, hedgerows and waterways) so that they have evidence of the gaps that could be improved.

It is still unclear at present exactly how local authorities will be monitoring maintenance over 30 years in practice. Other BNG details still being ironed out include what types of developments should be exempt from the requirement (e.g. de-minimus projects) and exactly how best to deal with phased sites.

In the meantime all developments need to start engaging with the requirement, ideally during site selection. It is of course far easier to design a scheme from the outset with the requirement in mind than it is to try and add it in later.

This means that, before any development begins, applicants need to measure the existing and proposed biodiversity values of their sites. They also need to set a clear plan for the proposed increase, and get that plan approved by their local authority.

But how will the condition actually operate?

Upon the granting of planning approval, the planning condition requires that a biodiversity gain plan be submitted – and approved – by the relevant local planning authority before any development can lawfully begin. The biodiversity gain plan must assess the value of natural habitats on-site before development and after development, and ensure that at least a 10% net gain is achieved between the values. You will need to engage a qualified ecologist for this.

It should be noted that you can resolve the requirement before the condition stage by including the net diversity plan in your planning application.

The act also makes clear that the biodiversity gain plan should address how adverse impacts on habitats have been minimised. After avoiding harm, biodiversity improvements can be delivered through wildlife habitat creation or enhancement.

It’s also worth considering that the requirement still applies for smaller sites, including householder applications, but local authorities could accept a lower net gain requirement if the development does not cause habitat loss. The integration of green infrastructure, for example, or bat and bird nesting features, could instead be encouraged.

The legislation raises many questions for anyone thinking about embarking on a building project.

At CAD Architects, we welcome this opportunity for planning to contribute to environmental improvement and we look forward to providing guidance and support to developers.

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