What is Biodiversity Net Gain?

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Biodiversity Net Gain (BNG) is an approach to development, and/or land management, that aims to leave the natural environment in a measurably better state than it was beforehand.

What is existing policy on biodiversity net gain (BNG)?
  • Planning policies and decisions should contribute to and enhance the natural and local environment by:
  • minimising impacts on and providing net gains for biodiversity, by establishing coherent ecological networks that are more resilient to current and future pressures
  • promote the conservation, restoration and enhancement of priority habitats, ecological networks and the protection and recovery of priority species
  • identify and pursue opportunities for securing measurable net gains for biodiversity and development whose primary objective is to conserve or enhance biodiversity
  • opportunities to incorporate biodiversity improvements in and around developments should be encouraged, especially where this can secure measurable net gains for biodiversity.
When determining planning applications, local planning authorities should apply the following principles:
  • development whose primary objective is to conserve or enhance biodiversity should be supported
  • opportunities to improve biodiversity in and around developments should be integrated as part of their design,
  • especially where this can secure measurable net gains for biodiversity or enhance public access to nature where this is appropriate.
What are the key components of mandatory 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.

But, this does not change existing legal protections for important habitats and wildlife species. It maintains the existing hierarchy:

  • avoid impacts first,
  • then mitigate and
  • only compensate as a last resort
It will apply to Nationally Significant Infrastructure Projects (NSIPs) but not marine development.

We expect a 2 year implementation period for mandatory BNG once the Environment Bill has received Royal Assent (which happened on 9 November 2021). The Act includes provision for secondary legislation to set a date for the requirement to come into force.

What is the Biodiversity Metric?
  • Demonstrating BNG requires an approach to measuring biodiversity.
  • The Biodiversity Metric is a habitat based approach to determining a proxy biodiversity value developed by Natural England.
  • The Biodiversity Metric is designed to provide ecologists, developers, planners and other interested parties with a means of assessing changes in biodiversity value.
  • Mandatory BNG will require use of the latest version of the Biodiversity Metric.
What is a Biodiversity Gain Plan?

The biodiversity gain plan is a document which sets out how a development will deliver biodiversity net gain and allows the planning authority to check whether the proposals meet the biodiversity gain objective.

The Environment Act sets out that the biodiversity gain plan should cover:

  • 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.
  • Government intends to publish a biodiversity gain plan template.
  • It also indicates that biodiversity net gain information will be required to be submitted at the planning application stage rather than a complete biodiversity gain plan.
What is the national Biodiversity Credits Scheme?
  • Firstly, The Environment Act makes provision for the Secretary of State to set up a system of statutory biodiversity credits that will be invested in habitat creation.
  • Secondly, the biodiversity credits scheme allows the UK government to sell biodiversity credits to developers if the required biodiversity net gains cannot be achieved on-site or through the off-site market.
  • Finally, the price of biodiversity credits will be set higher than prices for equivalent biodiversity gain on the market. The intention is that this system will be run by a national body, not at the local level.
When will we know what is classed as irreplaceable habitat?
  • The Environment Act includes provision to exempt irreplaceable habitats from the mandatory BNG requirement.
  • Natural England is currently developing new guidance which will set out the definition and a definitive list of irreplaceable habitats in England.
  • It is intended for guidance to be published in Spring 2023, and for this to form part of the forthcoming reform of national planning policy.


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