DEFRA will define ‘Net Gain’ to biodiversity, establishing the principle that planning permission should only be given if a new development project increases rather than reduces levels of biodiversity present on a site. Evidence of an increase in biodiversity will require a baseline assessment of what is currently present on a site and then an estimation of how proposed designs will add to that level, and latterly supported by post-construction evidence that a 10% gain has been delivered.

Measurement of pre and post-construction biodiversity levels will be based on DEFRA’s ‘Biodiversity Metric 2.0‘. DEFRA has proposed to use four components, each with specific ‘metrics’ or indicators, to create an indicative score for biodiversity quality on the site (and offsite where applied) pre and post-construction: