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Delivering BNG

Measuring BNG

Habitat value is measured using the Statutory Biodiversity Metric, which is a calculator tool for biodiversity. It works by assigning a unit value to habitats present within the development red line boundary, according on their importance for biodiversity. It then calculates how many biodiversity units will be generated post-development, accounting for both losses of habitat to the development footprint and habitats created and/or enhanced through the landscaping strategy.

The statutory biodiversity metric should be used for development which meets the definition for major development. The small sites metric (SSM) can be used for small sites, where the additional criteria in the SSM user guide are met. Even where the stated criteria are met, the SSM does not have to be used. The statutory biodiversity metric tool can always be used in its place.

The statutory biodiversity metric and the small sites metric should be completed in accordance with the biodiversity metric rules and principles set out in the Statutory Biodiversity Metric User Guide or the Small Sites Metric User Guide. Links to these can be found on the Validation, Guidance and Tools page

Degradation of Sites

There may be some instances where activities will have been undertaken prior to the submission of a planning application that will reduce the pre-development biodiversity value of the site. Where this has occurred since 30th January 2020 and is not in accordance with a planning permission, then the pre-development biodiversity value of the site should be taken to be its biodiversity value immediately before these activities were undertaken.

Biodiversity Mitigation and Spatial Hierarchy

Biodiversity net gain requirements do not replace existing protections and considerations afforded to protected and notable species and designated sites.

When preparing and designing development proposals to achieve BNG, applicants will need to consider and implement a range of measures, in line with the biodiversity mitigation hierarchy, which requires the following actions in the following order of priority:

  1. Avoiding adverse effects of the development on onsite habitat with a habitat distinctiveness score, applied in the biodiversity metric, equal to or higher than six;
  2. In so far as those adverse effects cannot be avoided, mitigating those effects;
  3. In so far as those adverse effects cannot be mitigated, habitat enhancement of onsite habitat;
  4. In so far as there cannot be that enhancement, creation of onsite habitat
  5. so far as there cannot be that creation, the availability of registered offsite biodiversity gain;
  6. In so far as that offsite habitat enhancement cannot be secured, purchasing biodiversity credits;

Developers are encouraged to follow the biodiversity gain hierarchy from the earliest stage possible when preparing and designing development proposals.

In addition to the biodiversity mitigation hierarchy, planning practice guidance sets out a sequential hierarchy of BNG delivery.

  1. Meeting the BNG requirement within a development site

The enhancement and creation of habitats on-site is the preferred option for the delivery of the biodiversity gain requirement to ensure that ecological connectivity and value is kept within close proximity to habitats that are being lost.

  1. Meeting the BNG requirement on other land owned by the developer

If a developer intends to meet part of their BNG requirements on land that they own outside of the red-line boundary of their development site, they will need to enter into a S.106 agreement with the council; and then register the off-site area with Natural England.

  1. Meeting the BNG requirement through the purchase of biodiversity units or statutory credits.

If unable to satisfy the BNG requirement through on-site or off-site habitat creation or enhancements, developers will either need to source any outstanding biodiversity units from a registered habitat banks or the statutory credit system in order to achieve biodiversity net gain. The Kent Biodiversity Sites Register lists available biodiversity units within Kent.

Spatial Multiplier

The statutory biodiversity metric incentivises habitat delivery on or close to the development site through a ‘spatial risk multiplier’, which reduces the biodiversity value of habitats delivered further away from the development.

Interim guidance on strategic significance in Kent and Medway has been developed for implementation across all of Kent’s local planning authorities. This interim guidance is aimed at the ecological advisors of planning applicants and landowners offering biodiversity net gain delivery sites and should be used in the biodiversity metric calculations.

The interim guidance will be superseded when the Local Nature Recovery Strategy (LNRS) for Kent and Medway is published.

Securing BNG

Any significant on-site biodiversity gains; and all off-site biodiversity gains must be secured by a S106 legal agreement for at least 30 years; and accompanied with a Habitat Management and Monitoring Plan.