• Habitat creation or enhancement where distinctiveness is increased relative to the distinctiveness of the habitat before development
• Areas of habitat creation or enhancement which are significant in area relative to the size of the development
• Enhancements to habitat condition, for example from poor or moderate to good

Gardens, under national guidance, cannot be considered significant; therefore, we expect no more than half of the Biodiversity Units of a development to be provided through a vegetated garden.

Most of development proposals within Exmoor are small in scale. Although such proposals may satisfy one or more of the criteria set out above, they frequently generate only fractional Biodiversity Units. Requiring these enhancements to be secured through a legal agreement may therefore be disproportionate. In such cases, and at the discretion of ENPA, Biodiversity Net Gain (BNG) may be secured by condition alone.

Notwithstanding this, where a proposal results in a post-development biodiversity value of one or more Biodiversity Units and qualifies as a significant enhancement, the enhancement must be secured through an appropriate legal agreement.

Exmoor National Park Authority reserves the right to secure gains in biodiversity of less than one Biodiversity Unit through appropriate legal agreement if it is considered significant, as above.

2.2.3 BNG Survey Requirements

To ensure that habitat types and conditions are accurately classified using the Statutory Biodiversity Metric, UKHab surveys should be undertaken during the optimum survey season for the habitats present. For most semi-natural habitats this will typically be during spring and summer when botanical indicators are most readily identifiable. Where habitat conditions cannot be reliably determined due to the timing of the survey, ENPA may require updated survey information before accepting the biodiversity baseline.

BNG surveys should cover the entire red line application boundary and include all habitats and linear features, including boundary hedgerows, that form part of the application site. Any exclusion of habitats from the baseline assessment must be clearly justified and agreed with ENPA prior to submission.

2.2.4 The Metric

The statutory biodiversity metric must be used for the calculation of pre-development and post-development biodiversity value of sites and projects.

The statutory biodiversity metric should be used for:

• Any development site where priority habitat is present
• Residential development of 10 or more dwellings on a site of ≥1ha
• Where the number of dwellings is not known the site area is ≥ 0.5ha
• For all other development types, the site area is ≥1ha or floorspace ≥1000m2

The metric should be completed by a competent person, normally an ecologist.

The small sites statutory biodiversity metric is a simplified version of the statutory biodiversity metric and may be used for small sites, which are defined as: