Biodiversity Net Gain

New Building in Dover
New build on agricultural land

About Biodiversity Net Gain

Biodiversity Net Gain (“Net Gain”) is a Methodology to help to stop developments which cause a decline in biodiversity. This will often mean that there will be greater protection for existing habitats on a site, as well as enhancement of habitats and the wider site. This enhancement can be through land management and/or habitat creation. There is usually a requirement to show a 10% Net Gain to obtain planning permission. In some cases, there may be a requirement for higher % of Biodiversity Net Gain. The Environment Act 2021 sets out the requirements for Net Gain.

Net Gain requirements apply to all developments that require planning permission under the Town and Country Planning Act 1990 (TCPA). The Net Gain requirement also applies to Nationally Significant Infrastructure Projects (NSIP) consented under the Planning Act 2008.


There are some exemptions from the requirement to show a Net Gain.
General Permitted Development. If your project is exempt from the TCPA under the Town and Country Planning (General Permitted Development) (England) Order 2015, then it is also exempt from the requirement for Biodiversity Net Gain.
If your proposals are for:

  • marine sites;
  • development that ‘results in negligible… or minimal impacts to low or medium distinctiveness habitats’ ;
  • householder applications such as building extensions;
  • change of use applications;
  • schemes covered by the Transport and Works Act 1992 and Highways Act 1980.

How is Biodiversity Net Gain Calculated?

The Biodiversity Metric 3.1 Calculator
Biodiversity Net Gain Calculator

Landvision use the Defra Biodiversity Metric. It is in widespread use in England. There are other metrics, but we do not use them. The Defra Biodiversity Metric measures net gain or loss by measuring pre development and post development change using biodiversity units or score. The basic calculation is:

Post-development biodiversity units


Pre-development biodiversity units

You will require an ecologist to undertake a survey of the site. Much like a PEA or Phase 1 Habitat Survey, the Metric requires that habitat type to be recorded along with:

  • habitat area;
  • habitat distinctiveness;
  • habitat condition;
  • ecological connectivity;
  • strategic significance.

For the post-development Metric calculation, all the above criteria are used along with:

  • time;
  • difficulty;
  • spatial risk.

If you have any questions or need answers to your queries, call us now on 01892 782200 to discuss your site requirements.