Measuring ecological change with Defra Metric 2.0

The Defra Metric tool 2.0 can be used to determine the percentage score that describes ecological change in Guidance Note 36 (Table 9: Reward Scale), if the following is also met:

  • A Suitably Qualified Ecologist confirms that they have used the Defra Metric tool 2.0 to measure ecological change in line with up to date good practice regarding the Mitigation Hierarchy and Biodiversity Net-Gain including CIEEM, CIRIA & IEMA, 2019, Biodiversity Net Gain. Good practice principles for development: A practical guide (
  • The Methodology sections of the relevant ecology assessment issues are followed
  • All other relevant criteria are met
  • One calculation tool is used consistently throughout the development to determine the change in ecological value. i.e. A mixture of outputs from the BREEAM Ecological Change tool and Defra Metric 2.0 cannot be combined

Alternatively, the BREEAM Change in Ecological Value calculator tool will continue to be accepted until stated otherwise. This is subject to change as part of transitioning to Defra Metric 2.1, once this has been finalised and released. The latest timescales and information on this are available from Natural England:

Edited 23/09/20:Β 

The BREEAM Ecological Change tool determines credits using the lowest ‘Post development percentage of Pre development’ score for the Area based and Linear habitats. If the Defra Metric tool 2.0 has been used, the ‘Total net % change’ results should be used to calculate this.

For example, if the Defra Metric 2.0 tool suggests that there is a net change of -65%, then the ‘Post development percentage of Pre development’ would be 35% for the purposes of BREEAM. Likewise, if the net change is +8%, then the percentage would be 108%.