What is Biodiversity?
Biodiversity is the variety of all life on Earth. It means how many different species there are, how varied they are, and where they are found. It includes everything from tiny soil microbes to large mammals and ancient trees. It also includes species that are rare, hard to find, or not yet discovered.
Biodiversity is a form of natural capital. High biodiversity supports vital ecosystem services such as food production and clean water. It also leads to leads to better outcomes for people.
Biodiversity in the UK is under serious threat. The UK is one of the most nature-depleted countries in the world, with 56% of species in decline. So, it is important that the design, and construction of new developments avoids harming species and habitats.
What is the Biodiversity Guide?
The Biodiversity Guide (updated 2026) is for designers and developers.
The guidance includes advice on:
- Legal protections for species and habitats
- Planning legislation and local policy
- Cornish hedges and hedgerows
- Habitat mitigation measures such as bat and bird boxes
- When to undertake professional ecological surveys
- Where to find support to prepare ecological evidence and plans
It also explains how to achieve Biodiversity Net Gain.
What is Biodiversity Net Gain?
Biodiversity Net Gain is an approach to development that aims to leave biodiversity in a better state.
It uses the ecological mitigation hierarchy with a biodiversity metric to measure the impact of development on biodiversity.
The Environment Act 2021 (legislation.gov.uk) makes a 10% Biodiversity Net Gain mandatory.
Developments must achieve this net gain within 30 years.
Cornwall was one of the first UK councils to introduce a local Biodiversity Net Gain policy. Since 1 March 2020, all major planning applications have needed to deliver at least 10%.
Biodiversity Net Gain uses the DEFRA Biodiversity Metric to measure biodiversity in units. This allows planners and developers to share common information in respect to biodiversity.
Key Information
- The Cornwall Climate Emergency Development Plan Document
- Biodiversity Net Gain Technical Guidance for Developers and Planners (In-depth guidance including Biodiversity Offsetting)
- Cornwall Planning for Biodiversity - updated 2026 (All aspects of all biodiversity in development.)
- Cornwall Council Planning Validation Guide (Submission requirements for Biodiversity Net Gain)
- DEFRA Biodiversity Metric Download User Guide and Metric Spreadsheet)
- CIEEM: Biodiversity Net Gain Report and Audit Templates (includes useful templates for Biodiversity Gain & monitoring reporting)
- BSI Standards BS 8683:2021 (Process standards)
- Planning Advisory Service (PAS) FAQ
Current Biodiversity Net Gain Planning Requirements
The requirements are set out in the Cornwall Council Validation Guide. There is also a dedicated Biodiversity Net Gain web page.
Requirements include:
- 10% Biodiversity Net Gain
- Submission of Biodiversity Gain Plan
- Submission of latest version of Biodiversity Metric (in an Excel format)
Key contacts:
- Ecology ecology@cornwall.gov.uk 0300 1234 202
- Local Plan localplan@cornwall.gov.uk 0300 1234 151