Overview
In England, most new developments will have to evidence deliver 10% biodiversity net gain (BNG). This is mandatory under Schedule 7A of the Town and Country Planning Act 1990, as inserted by Schedule 14 of the Environment Act 2021.
The ‘Biodiversity Net Gain’ tool is used to calculate biodiversity net gain based on the measurement and classification of habitats before and after development. Habitats are used as proxies for biodiversity. A habitat is a categorisation of a physical area based on environmental characteristics including geographical location, vegetation, and climate. While habitats do not cover all aspects of biodiversity, the advantage of using them as a proxy is the ease of collecting data and monitoring.
The tool uses standardised biodiversity units to represent the relative value of different habitat types, it is not an absolute measure of biodiversity loss or gain. It follows the statutory biodiversity metric methodology, the calculation tool designed to calculate biodiversity net gain, and is licensed to use the UKHab UK Habitat Classification system for full compliance.
Scope
The following data is required:
- Habitat data, including an assessment of their condition
- Local plans, strategies, and policies, relevant to the site area, to inform Strategic significance
- Planned changes to habitats from architecht and landscape architect drawings
Guidance
The tool contains separate queries and questions for On-site and Off-site areas and the three types of biodiversity unit available: area habitats (Habitats), terrestrial linear habitats (Hedges), and freshwater linear habitats (Watercourses). These units cannot be summed, traded, or converted between types and the requirement for 10% net gain applies to each individually if they are present on site.
Biodiversity units are calculated based on the size of a habitat and parameters representing its value based on the type of habitat. There are three core parameters used to determine habitat value:
Distinctiveness
Distinctiveness is a measure of the overall relative value of a habitat, considering factors such as species richness, rarity, and extent of any protected status. In other words, it is a fixed value for each habitat type based on relative value at a national scale.
Condition
Condition is a measure of a habitat against its ecological optimum state, to allow for variation in quality of habitats of the same type, to allow for variation in quality of habitats of the same type. Condition is determined by a Condition Assessment. Assessments vary by habitat, with some being more complex. Users evaluate each habitat against a set of criteria that describe the ecological optimum state, and the number of criteria achieved determines the condition. Click here to download the statutory biodiversity condition assessments from Defra.
Condition Assessments also act as a framework for habitat creation and enhancement, as the criteria inform good habitat design and management practices.
Strategic significance
Strategic significance describes the local value of a habitat, which may be higher than the national value, particularly in urban environments. It is determined by a qualitative review of geographically relevant plans and policies as well as through consultation with the relevant Local Planning Authority (LPA). Strategic significance enables users to highlight where habitats are locally important and may deviate from the national importance represented by the Distinctiveness parameter. This is particularly useful for urban developments, where individual trees or enhancements such as green roofs may not have a high Distinctiveness score but are prevalent in urban city planning policies.
Comments
0 comments
Article is closed for comments.