Biodiversity Net Gain

Development is a large part of our society today, with much more planned over the coming years. Many sites have already been allocated for development, which will, of course, impact biodiversity. However, one of the key elements of biodiversity net gain is that, for the first time, developers will have to measure and quantify their impact on biodiversity. They will also have to come up with a long term plan that will deliver at least 10% more of the biodiversity that is going to be negatively affected.

What is BNG?

Biodiversity Net Gain is an approach to development that leaves biodiversity in a measurably better state than before. It enables development to contribute to the recovery of nature whilst still developing land and ensures that habitat for wildlife is in a better state that prior to the development. Falling under the new Environment Bill and implemented through the Town and Country Planning Act, the Biodiversity Net Gain requirement aims to create new habitat, enhance existing habitats and to reduce and compensate the impact of developments on natural habitats in the UK. Mandatory BNG came into force in England on 12th February 2024.

Why do we need BNG?

The natural environment in the UK is under serious threat. There has been a deeply concerning decline in biodiversity, as well many other adverse trends, frequent failure to make progress towards targets, and a lack of progress in addressing existential risks, including from climate change.

By making biodiversity net gain mandatory by law, it can be ensured that vital steps are taken to protect and enhance vital habitats and wildlife in the UK.

What is mandatory BNG?

In England, BNG is mandatory under Schedule 7A of the Town and Country Planning Act 1990 (as inserted by Schedule 14 of the Environment Act 2021).
The Environment Bill (through the Town and Country Planning Act) sets out several mandatory elements of BNG:

  • Minimum 10% gain required calculated using the Biodiversity Metric & approval of a biodiversity gain plan;
  • Habitat secured for at least 30 years via planning obligations or conservation covenants;
  • Delivered on-site, off-site or via a new statutory biodiversity credits scheme; and
    National register for net gain delivery sites.
  • Does not change existing approach to protection of wildlife in the sense that it maintains the mitigation hierarchy of avoiding impact first.

What is the mitigation hierarchy?

The mitigation hierarchy is to be applied when delivering biodiversity net gain. The mitigation hierarchy is a framework which sets out how biodiversity loss can be avoided, minimised, restored and offset during development. The following sets out the key stages of the mitigation hierarchy that must be considered for each development:

Can significant harm to wildlife species and habitats be avoided; for example by locating the development on an alternative site with less harmful impacts?

Where significant harm cannot be wholly or partially avoided, can it be minimised by design or by the use of effective mitigation measures that can be secured by, for example, conditions or planning obligations?

Where, despite mitigation, there would still be significant residual harm, as a last resort, can this be properly compensated for by measures to provide for an equivalent or greater value of biodiversity

What are the existing policies for BNG?

The new Environment Act 2021 introduced a requirement that any new planning application for development will be required to meet the objective that the “biodiversity value attributable to the development exceeds the pre-development biodiversity value of the on-site habitat by at least [10%]”. From February 2024 min 10% BNG became mandatory and a material planning consideration (earlier time/higher% can be set by local policies). From April 2024 min 10% BNG became mandatory for small sites (<10 houses/<1Ha or for non-residential <1000m2 floor space/<1Ha.

How is BNG Measured?

The BNG metric is used for measuring biodiversity net gain. The metric is quite complex and so should be used by a competent person, normally an ecologist.

The BNG metric is used for baseline assessments of both the development site and any off-site mitigation sites. There are four key areas that the BNG metric measures:

  • Habitat size
  • Habitat condition
  • Habitat distinctiveness
  • Strategic Significance (is the habitat a priority or located in a priority or protected area)

These baseline assessments provide detail on what the current biodiversity value of the site is and what habitats are there.

What is a BNG plan?

A BNG plan is produced by developers and shall be submitted to the local authority for approval. Planning applications subject to mandatory BNG will be required to submit a biodiversity gain plan for planning authority approval and must include;
• How adverse impacts on habitats have been minimised;
• The pre-development biodiversity value of the onsite habitat;
• The post-development biodiversity value of the onsite habitat;
• The biodiversity value of any offsite habitat provided in relation to the development;
• Any statutory biodiversity credits purchased; plus
• Any further requirements as set out in secondary legislation.