26th June 2023

N-A-T-U-R-E : A Six-Point Guide to Getting Started with Biodiversity Net Gain Compliance

There are just five months to go until public sector building projects will need to ensure a minimum mandatory gain of 10% Biodiversity Net Gain (BNG) value.  Research has reported a 13% decline in the average abundance of wildlife in the UK since the 1970s and few would disagree that we can’t reverse this unless we take some action now.

Defra confirmed last month that the November 2023 deadline for compliance remains, with the exception of smaller sites which now have an extra 12 months (Nov 2024) to prepare and get their processes and procedures in place to meet the legislation.

Time is ticking and it is fair to say that many public sector organisations are still scratching their heads to know how to tick all the boxes to meet the deadline. BNG needs to be considered from planning and design right up to the 30-year guarantee management of the biodiversity at the site.  The Government will permit, in some cases, the delivery of net-gain through improvements away from the site, but developers will need to purchase credits. To date the details of this scheme have not been disclosed.

In the meantime, there is much that can be done in the here and now and this article offers a six- point checklist to get public sector organisations started. With each point linked to the word NATURE, hopefully this gives a memorable reference.


Let’s start with the numbers and the 10% Biodiversity Net Gain value requirement. It is effectively establishing a metric by which the impact needs to be assessed, monitored and reported and will be a mandatory minimum. However, when assessing any development, you also need to factor in the remediation, which means any biodiversity measures needed to get the development to a zero footing, from which is it possible to then add the 10% gain. For example, if a development is planned to reduce a site’s value in Biodiversity Units by 40%, then the development needs to plan a 40% remediation before planning the additional 10% uplift.

Consider how much BNG is going to cost as a percentage of the overall build cost and the current land value. The DEFRA calculator tool can help you to get a figure, by supporting you in assessing the biodiversity unit value of an area of land and measure and account for direct impacts on biodiversity. You can also compare proposals for a site – such as creating or enhancing habitat on-site or off-site. Brownfield sites are often easiest to develop from as they tend to have lower existing pre-development value in terms of Biodiversity Units. Offsetting will play a key role for those developments where it is difficult to achieve remediation, plus the additional benefit.