Is your Biodiversity Net Gain up-to-date?

The recently updated Biodiversity Metric 3.1 could mean some developments in England are no longer hitting the mark when it comes to biodiversity net gain.

And with a non-negotiable BNG needed to secure planning, this can be a big problem for those sites assessed before the updated metric came into place in April this year. Here, Director of Ecology, Mike Barker uses his experience on a recent solar project to show the impact of these changes and demonstrate why it’s advisable to review any projects assessed using previous calculators.

Changes to how we measure Biodiversity Net Gain

Biodiversity net gain is measured using DEFRA’s current BNG Calculator V3.1 which supersedes the previously used Biodiversity Metric 2.0 Calculation Tool Beta Test17.  

What does this mean for development?

Extra care will be needed where assessments were conducted using earlier versions of the metric calculator as the projected uplifts may no longer be correct. Reports submitted with planning proposals could feature incorrect data which could be challenged by local authorities subjecting the project to costly delays.

To ensure this doesn’t happen, we recommend BNG assessments completed before April 2022 are reviewed and remeasured.

Biodiversity Net Gain 3rd Party Reviews

Our 3rd party BNG reviews use the Biodiversity Metric 3.1 to remeasure a sites habitat credits and required net gain. We flag any potential ecological risks and suggest solutions to achieve BNG if needed.   

Our 3rd Party review in practice

We recently completed an initial ecological review of a proposed Solar Farm on behalf of our clients.

Our evaluation included an up-to-date search on Natural England’s Multi Agency Geographic Information for the Countryside1 (MAGIC) website.

Previous works had been undertaken on the site by another consulting company in 2021 but all assessments were completed using Biodiversity Metric 2.0 which meant they were out of date.

Our 3rd party review

As part of our 3rd party review, we evaluated the existing desk study data, online information and the following documents:

  • Biodiversity Metric Assessment
  • Ecological Impact Assessment
  • Ornithological Impact Assessment
  • Landscape and Biodiversity Management Plan
  • Outline Breeding Wader Mitigation Plan.

Our review aimed to flag any ecological risks apparent on site and demonstrate how the development could potentially achieve BNG based on the previous habitat data and our online observations.

Large solar panel at Warwick solar farm

Making complex easy for our clients

We transferred as much data as possible from the previous report and updated the BNG calculator to version V3.1. However, as this was an initial ecological review of what a full BNG assessment would conclude, we also recommended that an updated Phase 1 survey be completed.

Once complete, we found several aspects of the previous report that needed further investigation including:

  • Review and remeasure the development footprint

    Previous consultants had used a very tight definition of the development footprint which we recommended be reviewed and remeasured within a full BNG assessment.
  • Further condition surveys for grasslands

    We found a possible over-estimate in terms of habitat units generated, which would in turn result in uncertainty of the classification of the baseline grassland. We recommended that further condition survey work should be done to ensure the existing grassland is categorised correctly. If the baseline change is made the potential for BNG uplift could be even more. Although care must be taken not to rely on these without further site work.
  • Mitigation plan review

    Following the changes of the ‘trading’ rules, we found that the proposed habitat creation and enhancement requires further work. This was because units of ‘Arable field margins tussocky’ were lost and not compensated for like for like or with a higher value habitat. Further work on the proposed mitigation plan will be required to resolve this and this may have implications for the development layout and design, although the total area of this habitat is relatively small. We believe these changes are possible and could be delivered on site.

Our client also wanted to understand the scope for increasing the density of solar panels within the development. Given the surplus of habitat units generated on site, there was in principle an opportunity to fine tune the layout to reduce the grassland habitats, and to increase the development footprint.

In summary...

Our 3rd party review highlighted several unresolved queries regarding the BNG calculations both for defining the baseline and the post-development uplift. Now they have identified these areas of concern, our client can adapt their BNG plans to ensure their planning proposals deliver the required uplift and go on to secure the green light for development. 


Biodiversity - field of wild flowers

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