Evaluating biodiversity – how does the Defra Metric measure up?

Posted by Sara King BSc (Hons) MCIEEM on 1/02/2019

The Defra Metric was developed as part of a biodiversity assessment pilot project. Since the project concluded, it has been adopted by several local planning authorities across the UK as a way of quantitatively measuring the impact of proposed developments on biodiversity. The calculator uses baseline information, as well as details of the proposed development, its impact and impact mitigation, to generate expected changes in biodiversity. If the result is no net gain, then further on-site mitigation is required, and potentially off-site mitigation and compensation too.

Metric Mk 2

Defra are currently in the process of updating the existing metric, both to improve its accuracy, and to address feedback resulting from consultations. Under the UK's National Planning Policy Framework, all proposed developments must result in net biodiversity gain, so the objective is for the updated calculator to be integrated into all planning decisions made by UK authorities. It can also be used to evaluate various development options from a biodiversity perspective, based on their impact and the level of mitigation required, giving developers and local authorities clarity, and decreasing the chance of unexpected outcomes at the planning stage.

A better, all-round solution

The updated Defra metric may be an improvement on its predecessor, but it is far from being a comprehensive solution. While it provides a quantitative assessment of impact and mitigation for development schemes and proposals, it does not assist landowners with biodiversity assessment - and this is where it falls down.

It is critically important that large landowners, such as utility companies and quarries, are be able to assess the biodiversity baseline of all their landholdings. This allows targets to be set in relation to net gain, as well as records kept of the impact of schemes on overall biodiversity.

For example, if a proposed development results in biodiversity loss, the ideal calculator will trigger an offset, thereby ensuring a net gain in biodiversity across the entire site. The ranking database generated by such a calculator can also be used to track changes in biodiversity resulting from management change, which frequently results in less intensive management and associated cost savings. This approach has been adopted by several UK water companies, as well as other large landowners, to ensure that they are meeting net gain targets.

So what alternatives are there to the Defra Metric? The Habitat Valuation Calculator developed by Ecosulis builds on Defra's offering to provide a far more comprehensive and bespoke calculator for landholding biodiversity assessment. This innovative tool, combined with the efforts of our specialist biodiversity assessment team, means we are leading the way when it comes to creating and monitoring biodiversity audits, allowing us to compare sites and predict outcomes efficiently and accurately. Feedback from a range of satisfied clients pays testament to this.


If you would like to discuss biodiversity assessment and the Habitat Valuation Calculator further, please contact Sara King, Biodiversity Assessment Specialist at Ecosulis (sara.king@ecosulis.co.uk)

Related Information: Ecosulis Biodiversity Assessment Tools: http://www.ecosulis.co.uk/biodiversity-quality-calculator-bqc

Bristol Water Landholdings: http://www.ecosulis.co.uk/case-study/bristol-water-landholdings