Biodiversity Net Gain
The Environment Bill 2019-21 is being currently considered by Parliament. The bill makes the provision of targets, plans and policies for improving natural environment. The National Planning Policy Framework has already introduce the concept of ‘Net Gain’ for biodiversity, which several local planning authorities have adopted.
Natural England is publishing finalised The Biodiversity Metrix 2.0 which is a way of measuring the biodiversity losses and gain from developments. This model is intended to update and replace the original Defra metric.
How is an assessment carried out?
A Biodiversity Net Gain calculation compares the baseline habitat against the post-development habitats. Biodiversity Net Gain is achieved if the post-development habitat provides a net gain improvement in regards to the biodiversity for a site.
The following steps are required:
- A site survey is carried out to assess the baseline habitats;
- The post-development plan for the site is defined, showing habitat areas;
- The baseline and post-development habitats are assessed using the biodiversity metric.
- The Biodiversity Net Gain, or loss, is calculated by comparing the difference between the baseline habitat units, and the post-development habitat units.
How many metrics are there?
There are several biodiversity metrics around so it is essential to establish which one is to be used before the Biodiversity Net Gain calculation is carried out. The Natural England ‘Biodiversity Metric 2.0 is the most common, but other organisations and local planning authorities have their own metrics.
How are Habitats calculated?
Habitats are assessed based on the terrestrial area, terrestrial linear features, and aquatic linear features.
Where biodiversity net gain cannot be achieved on site then there may be the option for offsite enhancement measurements to be considered.