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Cornwall planning for Biodiversity Guide

What is Biodiversity?

Biodiversity is the variety and variability of life on Earth. It is a form of natural capital that helps to create and maintain our eco-system services. Our biodiversity is in a fragile state and the UK is one of the most nature-depleted countries in the world. 56% of our species are in decline. It is important that the built environment does not cause the loss of biodiversity.

What is the Biodiversity Guide?

The Biodiversity Guide (updated 2023) explains how to deal with biodiversity within the planning process.

It gives advice on every aspect of biodiversity within planning. This includes:

statutory protections, planning legislation, hedgerows, bat and bird boxes and survey requirements. It explains how to secure net gain within the National Planning Policy Framework.

What is Biodiversity Net Gain?

Biodiversity Net Gain is an approach to development. It leaves the natural environment in a better state than beforehand.

It uses the ecological mitigation hierarchy with a biodiversity metric to measure the impact of development on biodiversity.

The Council’s net gain approach

The Council’s net gain approach

The Environment Act 2021 ( makes a 10% Biodiversity Net Gain a mandatory rule for major development in planning from January 2024. Developments must achieve this net gain within 30 years. Cornwall Council is committed to environmental growth. The Council has required a 10% net gain for all major applications since 1st March 2020.

Cornwall Council is committed to environmental growth and has introduced Net Gain in advance of the Environment Bill 2019-2021. The Chief Planning Officer Note did require a 10% net gain for all major applications since 1st March 2020.

Biodiversity Net Gain uses the DEFRA Biodiversity Metric to measure biodiversity in units. This allows planners and developers to speak the same language and facilitates mutual understanding in how development impacts on the natural world. Cornwall was one of the first councils in the UK to adopt a Biodiversity Net Gain policy at a local level.

Key Information

Current Biodiversity Net Gain Planning Requirements for major development:

  • Current Biodiversity Net Gain Planning Requirements for major development:

    • Demonstrate 10% Biodiversity Net Gain
    • Submission of Biodiversity Gain Plan
    • Submission of latest version of Biodiversity Metric


Although a national requirement for 10% biodiversity net gain will now not apply until January 2024, the Cornwall requirement for biodiversity net gain on major developments remains in place.

Applications should continue to make provision in line with policy G2 of the Climate Emergency DPD (February 2023) and meet the current local validation requirements. This includes the submission of the latest DEFRA metric. Applications validated in advance of mandating in January 2024 will be determined in line with Policy G2 of the CEDPD.  

See the Planning Validation Guide for further details on submission requirements.

Forthcoming changes to Biodiversity Net Gain Policy

  • Minor developments: The Cornwall Climate Emergency Development Plan Document includes minor developments in its net gain policy. Minor developments will therefore soon need to use the recently released Small Sites Metric.  The council will publicise this introduction through this webpage and through validation updates. It will also introduce to the Planning Agents forum.

Key contacts:

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