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Biodiversity Net Gain

What is Biodiversity Net Gain?

Biodiversity Net Gain

Biodiversity Net Gain (BNG) is an approach to development that leaves habitats and species in a better state than before. Where a development has an impact on habitats or species, BNG encourages developers to provide an increase in appropriate natural habitat and ecological features over and above that being affected, in such a way  that the current loss of biodiversity through development will be halted and ecological networks can be restored. There will be a 2-year transition period following the royal assent, so it is anticipated that BNG will become a  mandatory part of the UK planning process in autumn 2023.  

BNG still relies on the application of the mitigation hierarchy to avoid, mitigate or compensate for biodiversity losses. It is additional to these approaches, not instead of them. Put simply, it involves the use of a metric (the biodiversity metric) as a proxy for recognising the negative impacts on habitats arising from a development and calculating how much new or restored habitat, and of what type, is required to deliver sufficient net gain.

BNG for Developers

BNG is expected to become a mandatory part of the planning process across the UK, with many local authorities seeking a minimum of 10% gain for developments. For many developments this will be difficult to fully achieve onsite and so many will seek to deliver this net gain offsite. This process is called biodiversity offsetting, whereby landowners can provide opportunities for offsets to developers, calculated using an appropriate metric tool.

The metric tool reduces confusion around the magnitude of impacts, what level of mitigation is required and whether compensation (and how much) is needed. With such losses and gains quantified, local authorities and developers are ‘speaking the same language’.

BNG for Landowners

Landowners can provide opportunities to developers for offsets who, as a result of the requirements of planning policy, must provide compensation for biodiversity loss resulting from development activity. An offset provider delivers a quantifiable amount of biodiversity benefit to offset the loss of biodiversity resulting from development.

The losses and gains are measured in the same way, even if the habitats concerned are different. The measurement is done in ‘biodiversity units’, which are the product of the size of an area, and the distinctiveness and condition of the habitat it comprises. The assessment of biodiversity units lost and gained can be calculated using an appropriate assessment tool.

BNG pic


Offsets can involve habitat expansion (creation) or restoration:

  • expansion (creation): establish priority habitat on land where it is not present and where no significant relicts of the habitat currently exist; and
  • restoration: improve the condition of the existing habitat resource.

Offset providers must provide additional benefits: offsets cannot be designed simply to maintain condition or extent.

Note that if the developer chooses to meet their planning obligations by purchasing offsets from someone else, it is the units of biodiversity gain that are sold. The developer is not buying the biodiversity itself, or the land that it stands on. The units are units of biodiversity: they are not an attempt to put a price on biodiversity.

How we can help

Wildwood Ecology has been helping developers and landowners deliver the best outcomes for biodiversity since 1998.

We are experts in ecological surveys and can assess the baseline ecological value and condition of your site using the latest tools.

For developers, we will work alongside you to deliver the best outcomes for your site. We will look at what impacts are likely to occur and how best to address them on-site, as well as discuss off-site opportunities.

For landowners, we will work alongside you in helping decide the long-term aim for your site,  whether this be habitat expansion (creation) or restoration. Together we can advise on what biodiversity units you could offer for sale, securing the best outcomes for you and wildlife.

Useful links

Link to CIEEM:

Link to the British Standard Publication:

For more information about Biodiversity Net Gain please get in touch