Today the Government published its response to last August’s consultation on the Defra Metric 3.1. IEMA’s Policy and Engagement Lead on Biodiversity and Natural Capital, Lesley Wilson, tells us more about it.

Photo by Allyson Beaucourt

Today the Government published its response to last August’s consultation on the Defra Metric 3.1. IEMA’s Policy and Engagement Lead on Biodiversity and Natural Capital, Lesley Wilson, tells us more about it.

In August 2022 Defra launched a consultation on the Biodiversity Metric 3.1. The Metric is an essential tool that will underpin the success of the Biodiversity Net Gain (BNG) requirements coming into legislation in November 2023. Last September IEMA hosted a members’ workshop to create a response to the consultation.

The consultation focused on the spatial risk multiplier values, general improvement, guidance requirements for users, and the need for training.

The proposals from organisations responding to the consultation are interesting in themselves, but here we will concentrate on the proposed changes from Defra, much of which was a promise to look into suggestions in more detail.

Technical changes to the Metric will be:

  • Changing the formula of the spatial risk multiplier - the spatial risk multiplier will be applied as a constant to the offsite unit change (the difference between gains and losses)
  • Providing a summary of the results on each calculation tab in the metric to make it easier to follow the progress towards net gains as changes are made
  • Improving the formatting and user experience with additional error flags, colours, and notes within the tool to inform users of the implications of inputs; and
  • Fixing minor errors that were present in biodiversity metric 3.1

In guidance documents to the Metric, Defra has carried out some tidying up to condense some parts, remove duplication, improve formatting, and clarify sections where needed.

There was no real outcome on suggested case studies and it seems that Defra do intend to take proposals on board and periodically produce guidance. Where suggestions for case studies were more relevant to the BNG implementation then Defra will take this into account when creating that.

For minerals, it seems that Defra will offer more scope for deciding appropriate multipliers through the Metric rule that permits deviation from the Metric methodology in exceptional circumstances and providing a case study on how mineral development should apply in the Biodiversity Metric.

Responses with regard to case studies – including IEMA’s – looked for better guidance on irreplaceable habitats. There will be secondary legislation that sets out which habitats are considered irreplaceable for the purposes of BNG, and therefore not subject to the BNG requirement. Defra intends to hold a consultation on the definition of irreplaceable habitats including alignment with the National Planning Policy Framework to be held alongside draft secondary legislation. IEMA will let you know when this consultation comes out.

There have been a lot of questions around including species in the Metric, and Defra intends to keep them outside of it. Instead, Defra will try to capture this information in the Biodiversity Gain Plan. This could be done as part of an EIA, as suggested by IEMA members.

There will be no requirement for formal training for using the Defra Metric however there will be a recommendation that those using the Metric will be ‘competent’. For this, they reference British Standard BS 8683 on biodiversity net gain: ‘A competent person is someone who can demonstrate they have acquired through training, qualifications or experience, or a combination of these, the knowledge and skills enabling that person to perform specified tasks.’ The rivers and streams condition assessment has existing training and accreditation requirements and remains unchanged.

Lastly, the Biodiversity Metric will also be applied to NSIPs (Nationally Significant Infrastructure Projects) with no alteration to Metric multipliers.

What next? The changes to this Metric (to create Biodiversity Metric 4.0), including the Small Site Metric, will form the basis of the statutory Metric coming out in November.

If you’re interested in finding out about Biodiversity Net Gain in practice, you can watch IEMA’s series of webinars on BNG implementation. Our next webinar on monitoring and managing is on 22 March.

Photo of Lesley
Lesley Wilson

Policy and Engagement Lead

Lesley is Policy and Engagement Lead at IEMA with a focus on biodiversity and natural capital. Lesley also supports IEMA’s role as Secretariat to the UK Business and Biodiversity Forum, working with businesses to raise the profile of, mainstream, and share good practice in, biodiversity. Lesley joined IEMA in December 2021 after 11 years delivering projects, programmes and solutions for business in the field of environmental sustainability for the British Standards Institution (BSI), including ground breaking standards in biodiversity net gain and natural capital. Lesley has a qualification in business management (MBA) and climate change management, and mentors environmental students at the University of Westminster.


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