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Joanna Bryan

Chartered Legal Executive - Uckfield

4th November 2019

Biodiversity net gain and land development

What is biodiversity and biodiversity net gain?

Biodiversity is the different plant and animal species that may live in one place, such as a development site. It could include trees, plants, animals, fungi and even microorganisms.

The Government’s landmark Environment Bill is set to introduce tougher environmental protection and governance. It tackles biodiversity loss, climate change and environmental risks to public health in line with the 25 Year Environment Plan. One of the Environment Bill’s key measures is ‘biodiversity net gain’. The Bill will contain provisions that will require developers to demonstrate a 10% increase (or gain) in biodiversity on or near development sites.

Furthermore, the Bill will require developers to deliver habitat creation or enhancement to be maintained on site for a minimum of 30 years. The developer will be bound to this through conservation covenants with a ‘responsible body’ such as the local authority.

Who is affected?

Developers will be required to make an assessment of the baseline biodiversity units on the site prior to the development and determine what the post-development biodiversity units will be. Assessment will be based on Defra’s Biodiversity Metric 2.0 which is currently under consultation (you can respond until 31 December 2019).

How is biodiversity net gain calculated?

Baseline biodiversity units are likely to be calculated using the following metrics:

  • Distinctiveness – the score is assigned based on DEFRA’s habitat classification
  • Condition – the score is based on DEFRA criteria associated to different habitats
  • Strategic significance – the score is based on landscape-scale factors defined nationally and locally
  • Habitat connectivity – the score is based on ‘habitat aggregation’ calculation

Post-construction biodiversity units are likely to be calculated using the following metrics:

  • Distinctiveness
  • Condition
  • Strategic significance
  • Habitat connectivity
  • Spatial risk –distance of offset from the site
  • Temporal risk – time for the habitats to reach the target condition
  • Delivery risk – difficulty of new habitat creation

Biodiversity net gain is the post-development biodiversity units minus the baseline biodiversity units.

How will it be administered?

Natural England will be responsible for rolling out the biodiversity net gain requirement through a series of Local Nature Recovery Strategies to map out current biodiversity levels and areas for enhancement. The Strategies will work with Local Environment Record Centres which already monitor historical and current biodiversity data.


Exempt sites will include major infrastructure projects and marine sites, certain urban brown field sites that will have genuine viability issues and building extension projects will also be exempt. Smaller minor development sites which are those with fewer than 10 residential units will be offered a simplified requirement likely to be lower than 10%.


Off-site compensation will be an option but only after the developer has been through Defra’s migration hierarchy process. This involves four stages: Avoid, Minimise, Remediate and finally Compensate.

The first stage is avoiding, where habitat damage should be avoided. The second stage is minimise, where possible the habitat damage and loss should be minimised. The third stage is remediation, where possible, any damaged or lost habitat should be restored. As a last resort the damaged or lost habitat should be compensated for off-site.

Irreplaceable habitats will not be able to use this migration approach. These include ancient woodland, ancient and veteran trees, blanket bog, limestone pavements, sand dunes, saltmarsh and lowland fen.


Any developers that clear sites illegally before seeking planning permission will be subject to serious penalties. This is due to the requirement to submit biodiversity evidence as part of the planning process which will be checked against Record Centres.

The Environment Bill has passed its second reading in the House of Commons and is currently at committee stage.

If you require legal advice about biodiversity within the planning process please contact either Joanna Bryan, Chartered Legal Executive, or Oliver Bussell, Partner, in Rix & Kay’s Environment & Planning team.

Joanna recently presented at a morning seminar providing an Introduction to Biodiversity Net Gain. For more information click here to download the slides.


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