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Biodiversity Net Gain FAQs


What is Biodiversity Net Gain?

Under the Environment Act developers of all sizes are required to offset any harm to biodiversity on their site, and to achieve a 10% gain in the original levels.  Biodiversity is measured by habitat, being a proxy for biodiversity, using a DEFRA designed Metric.  The resulting output of baseline habitat units must then be compensated for.

How do BNG units work?

Having measured their baseline habitat units developers must achieve the same number of units, plus 10% at the end of the development.  Ideally this is done on the development site, through the creation of for example wildflower meadows, but if this is not possible the developer is able to purchase units from an offsetter such as The Iford Biodiversity Project

Is BNG mandatory?

From January 2024, The Environment Act 2021 stipulates that new housing and commercial developments must provide a 10% Biodiversity Net Gain if they result in a loss or degradation of habitat. For smaller projects, this date is April 2024.


BNG will apply to developers, land managers and local planning authorities, for any development that requires:


  • Planning permission granted under the Town and Country Planning Act 1990 (as amended) (the 1990 Act), where the development must provide at least 10% of Biodiversity Net Gain.

  • Development consent as a NISP granted under the Planning Act 2008. The BNG will need to be set out in a Biodiversity Net Gain statement or where the relevant national policy statement covers it.

How can The Iford Biodiversity Project help?

Our extensive experience in providing a BNG offset solution places us in a unique position to be able to assist developers in satisfying the needs of their Local Authority.  We can assist with the metric calculations, suggest tweaks to make the units requirements lower and engage with the LPA to ensure that an offset at Iford meets their needs as well.  Our partnership with South Downs National Park also provides reassurance to the LPA.  

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