“Biodiversity Net Gain (BNG) is an approach to development and/or land management, that aims to leave nature in a better state than it was beforehand”
Since April 2024 Biodiversity Net Gain has been mandatory, by law, on all planning applications in England above householder. BNG means that a development has to provide a 10% net gain in biodiversity from the original baseline of the development site. For example, if the development site had a baseline of 10 BNG units the site would have to create 11 BNG units post-development.
As set out in the Environment Act 2021, BNG habitats have to be in place for 30 years and aim to replace habitats like for like or better. All planning applications are subject to this legislation accept for those exempt which include:
- Existing planning permissions (made before the 12th February)
- Variations of planning permission
- Developments below the threshold (less than 25 square metres of onsite habitat or 5 metres of onsite linear habitat)
- Householder planning applications
- Self and Custom Build applications
- High speed rail transport network (High Speed Rail Act 2013)
- Urgent crown developments
- Developments that are granted planning permission by a development order (including permitted development rights)
How is it calculated?
Biodiversity Net Gain is calculated using the Defra Statutory Biodiversity Metric 4.0, created by Defra and Natural England which gives the ecology and habitats of the site a numerical value based on condition, size distinctiveness and strategic significance of the habitat type. The metric categorises the habitat in groups and based on these groups certain rules must be followed to ensure that an improved outcome for nature is being achieved. This means that, depending on the type, habitats have to be replaced as minimum like-for-like, or in some cases a “better” habitat has to be proposed to meet these rules
Onsite vs Offsite
Net gain provisions should be based on the mitigation hierarchy to prevent the destruction of habitats however that is not always possible for development. However, this should be taken into consideration at the very beginning of the design for developments to ensure that all measures have been taken to reduce the impact on habitats. If losses must happen, then the first stage would be to replace the habitats that have been degraded on the development site as part of the proposed scheme. This could include landscaping, public open space and urban trees. But, this is not always possible depending on the baseline of the site and the density of the scheme and therefore the next step would be to use offsite units. If an offset site cannot be found then Statutory Credits can be purchased from the government to offset. These are priced considerably higher than market value offsite credits.
Where offsite units are being purchased it is important to take into account the spatial multiplier which can be found in the metric. This means that the developer buying credits is penalised for going outside National Character Area (NCA) or Local Planning Authority (LPA) Boundaries. The spatial multiplier means that it takes additional land to provide the same number of units and depends on whether you are in a neighbouring LPA or NCA or the rest of the country. Where the offset site is in the neighbouring NCA the multiplier is 1.5 and any other area of the country the multiplier is 2.0
Legals
Biodiversity Net Gain habitats can be legally agreed by either Section 106 agreements agreed with an LPA or with Conservation Covenants with a Responsible Body. The legal agreement will ensure that the habitat is in place for 30-years and is monitored and managed in line with the Habitat Management and Monitoring Plan. There will also be a charge on the title which protects the habitat bank if the land were to be sold or transferred.
Once a legal agreement has been secured the habitat bank can be submitted to the Biodiversity Gain Sites Register created by Defra. The register has been designed to record all offsite BNG sites to ensure there is no double counting of credits and provide oversight into the BNG process. All significant information is stored in the register including a site location, baseline, uplift and unit allocations. It is important to note that, under BNG guidelines offsite units cannot be allocated to a development without the offsite site being registered.