FAQs about BNG

Why must development schemes provide BNG in addition to planning policies that already require net uplift in biodiversity for a site?

In recognition of the decline in the health of biodiversity across England, the Government drew up proposals requiring most forms of development that require consent in England to additionally demonstrate (at the time of writing) at least 10% uplift in BNG as measured against the Government's relevant metric, under section 98 of the Environment Act 2021. However, it is understood the Secretary of State has the power to vary this percentage requirement.

Are there any exemptions to the 10% BNG requirement?

There are some exemptions to this set out in the legislation. Upon receipt of a valid planning application, the Council will reach a view over whether the scheme qualifies for any of these exemptions (for example the 'de minimus' exemption) based upon the submitted particulars (including the advice of any retained qualified ecologist).

How does a developer calculate the pre-existing baseline habitat values on a site, and therefore the biodiversity units required for a 10% uplift?

Under the legislation developers must use the appropriate Government metric (small sites or standard metric). This is to ensure consistency across England and avoid situations where 3^rd party metrics may underestimate the necessary uplift. Note that the metric provides separate calculations for the three habitat types [area-based /linear-based /waterbody based].

Why must a developer ensure that a habitat is monitored and maintained for a 30-year period?

This is to ensure the survival of a habitat after its creation, i.e. to avoid schemes (accidently or deliberately) circumventing the requirement to achieve BNG.

When must habitats be created when a scheme is issued planning permission?

The BNG requirement automatically applies so will not be expressed as a planning condition on a consent however the Council will attach planning conditions to all BNG-applicable schemes, that will require the submission of final-BGPs and HMMPs before commencement of development. Also, the Council will condition the scheme requiring that habitat creation commences before commencement of the development (in other words, that the BGP is implemented before development commences).

Why do some types of development require a legal agreement whilst others do not?

The Council will require demonstration of some form of legal agreement with itself (or conservation covenant with a 3^rd party "responsible body") only where a scheme proposes delivery of some form of "significant habitat" either on-site, or at some other off-site location. This requirement does not apply to non-significant habitats (see www.local.gov.uk/pas/events/past-events/biodiversity-net-gain-local-authorities/biodiversity-net-gain-faqs).

Why is there variation in cost for the purchase of biodiversity units?

In the case of off-site biodiversity unit provision, the Government has deliberately applied factors pertaining to both "strategic significance", and "spatial risk multipliers". Both of these factors have the effect of rewarding off-site locations that are within, or close to areas favourable to strategic or local biodiversity creation. This also ties in with new requirements for (usually) County Councils to prepare Local Nature Recovery Strategies at the County-level. According to the biodiversity hierarchy developers are expected to demonstrate that they have tried to integrate BNG within the actual development site - where this is (totally or partially) not possible developers must source the appropriate biodiversity units from off-site locations such as commercial habitat banks. As a last resort the Government provides a national bank for statutory credits (which are priced accordingly expensive given the above factors).

Where should off-site biodiversity units come from?

It is the developer's responsibility to decide where and how to source any required off-site BUs - Councils cannot direct the developer to a particular commercial site, or company etc. Also, Councils cannot show favouritism towards, for example any Council- or public-run habitat banks. Given the factor of strategic significance and spatial risk multipliers, locally sourced units which accord with priorities identified in relevant strategies (such as Local Nature Recovery Strategies) may provide the most cost benefit to a developer.

Why are conservation covenants sometimes used instead of legal agreements (or S106 agreements)?

Conservation covenants are typically utilised where the developer is seeking agreement with a formal "responsible body" to ensure habitat delivery.

S106 agreements are with a Local Planning Authority only.
There are some differences between the two types of agreements, explained here -www.dentons.com/en/insights/articles/2025/april/1/conservation-covenants-v-section-106-agreement.

Note that a Council cannot enter a legal agreement with a developer where that Council is itself responsible for monitoring/managing delivery of the habitat upon its own land (unless the organisation sets up an arm's length corporate "vehicle" for this purpose). Therefore, developers may continue to choose (in the case of delivery of "significant habitats") which legal mechanism they pursue to ensure habitat delivery.