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Biodiversity Net Gain

Introducing a requirement for Biodiversity Net Gain in Cornwall

Chief Planning Officer’s Advice Note Consultation

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Cornwall Council has consulted on the Chief Planning Officer Advice Note which explains the Council’s current approach and provides further guidance on how to make an application.  The consultation period closed on the 21st May 2020 and the Council thanks respondents for their opinions.  A response and updated Chief Planning Officer Advice Note is now being prepared.

You can contact the Local Plans Team e-mail if you have any questions about the document.

What is Biodiversity?

Biodiversity is the term that is used to describe the variety of all life on earth. It includes all species of animals, plants and everything else that is alive on our planet. Habitats are the places in which species live. These species and their habitats contribute to the ecosystems services. These provide substantial benefits to people and the economy.

The UK is amongst the most nature-depleted countries in the world with 56% of our species in decline.  Over the past 50 years habitats have been eroded by:

  • increasingly intensive farming methods
  • man-made developments

Cornwall Council is now addressing how it can continue to provide the housing and commercial developments necessary for the region’s economic and social prosperity, while simultaneously reversing the decline in Biodiversity.

How do you measure Biodiversity?

DEFRA have produced a Biodiversity metric. This is based on trials performed in the UK since 2012. This metric scores different habitat types according to a predetermined relative biodiversity value. This value is then adjusted depending on the condition and location of the habitat. This allows a qualified ecologist to calculate ‘biodiversity units’ for a specific project or development.

The change in biodiversity units is determined by subtracting the number of pre-intervention biodiversity units (i.e. those originally existing on-site and off-site) from the number of post-intervention units (i.e. those projected to be provided).

What is Biodiversity Net Gain?

Biodiversity Net Gain is a new approach to development. It aims to leave the natural environment in a measurably better state than beforehand.  

It will require developers to ensure habitats for wildlife are enhanced. It requires a demonstrable increase in habitat value compared to the pre-development baseline.

By measuring the value of existing habitats in Biodiversity Units the Net Gain approach firstly encourages habitats of high biodiversity value to be avoided or preserved, given the difficulty and cost in compensating for them.  It also leads to new developments integrating wildlife enhancing features into plans in order to boost their score of biodiversity units.  Such enhancing features might include:

  • trees
  • hedges
  • wildflowers
  • ponds
  • other habitats 

What is the Mitigation Hierarchy?

Net Gain follows the principle of the mitigation hierarchy which seeks to:

  1. Enhance habitat
  2. Avoid habitat loss
  3. Minimise habitat loss
  4. Restore habitat loss
  5. Compensate for habitat loss
  6. Offset Habitat loss

Therefore Net Gain is not a ‘licence to trash’. The mitigation hierarchy must still be followed. Any loss of biodiversity on site in favour of the creation of an off-site gain will only be allowed in exceptional circumstances.  Any requirement for off-site provision will be taken as an exception. In such cases a mitigation payment will be sought through a Legal Agreement. However we are still agreeing a way forward to better tackle this issue.

When will net gain become a requirement?

The National Planning Policy Framework and the Cornwall Local Plan already requires a net gain in terms of planning policy. However, to increase predictability the government announced in the 2019 Spring Statement that Net Gain would be made mandatory.

The council does not yet have a firm date for when Net Gain will become nationally mandatory. Cornwall Council will however be applying a 10% net gain requirement to all major planning applications from 1 March 2020.

Ecological consultants will therefore need to ensure that data collected in 2019 and thereafter is suitable for use within the DEFRA 2.0 calculator. The metric and a user guide can be downloaded at the link below.

How will Net Gain affect major planning applications?

Submissions will need to demonstrate that:

  • The Mitigation Hierarchy has been followed (including proposals for any necessary compensation)
  • How the proposal will provide a minimum 10% net gain increase in biodiversity
  • How the proposal will integrate into any wider green infrastructure network.   

Definition of Major development:

  • 10+ dwellings / over half a hectare / building(s) exceeds 1000m²,
  • Office / light industrial - 1000+ m² / 1+ hectare
  • General industrial - 1000+ m² / 1+ hectare
  • Retail - 1000+ m²/ 1+ hectare
  • Gypsy/traveller site - 10+ pitches, Site area exceeds 1 hectare)

In line with DEFRA recommendations developments will be monitored for up to 30 years. This is to ensure that they accord with their biodiversity obligations. These obligations will be secured by way of planning conditions.

How will this affect minor planning applications?

The Government are currently exploring whether minor developments should be subject to longer transition arrangements or a lower net gain requirement than major developments.    

At a local level Cornwall Council is exploring an approach that either simplifies the metric or uses a points system. This should encourage the retention of existing habitat and the introduction of small scale changes that increase biodiversity on a plot by plot basis.

The council will be publishing further information on the net gain requirements for minor developments later in 2020.

Definition of Minor development:

  • 1-9 dwellings (unless floorspace exceeds 1000m² / under half a hectare
  • Office / light industrial - up to 999 m²/ under 1 hectare
  • General industrial - up to 999 m²/ under 1 Hectare
  • Retail - up to 999 m²/ under 1 hectare
  • Gypsy/traveller site - 0-9 pitches

What development will be exempt?

Policy Context

In March the Chancellor of the Exchequer announced that the government will introduce a new mandatory requirement for developments in England to deliver biodiversity net gain. Whilst this has not yet been put into place, the National Planning Policy Framework already requires net gain, stating that:

  • planning policies and decisions should minimise impacts on and provide net gains for biodiversity

Local policy context is set out in Policies 23 and 28 of the Cornwall Local Plan and the Environmental Growth Strategy.

Cornwall Local Plan Policy 23 sets out the relevant policy in relation to protection of the natural environment and the securing of net gains for biodiversity.  The policy states that: -

  • Development should avoid adverse impact on existing features as a first principle and enable net gains by designing in landscape and biodiversity features and enhancements … alongside new development.
  • Where adverse impacts are unavoidable they must be adequately and proportionately mitigated … compensation will be required as a last resort.

Cornwall Local Plan Policy 28 sets out the relevant policy in relation to the provision of infrastructure. The policy states that:

  • Developer contributions will be sought to ensure that the necessary physical, social, economic and green infrastructure is in place to deliver development.
  • Contributions will be used to provide or enhance local infrastructure that is adversely affected by the development of a site, but which will not be delivered on that site.

What will be required for applications?

Development applications will proceed as normal. However, they will be informed by figures for biodiversity losses and gains on sites.

All major applications will be required to submit a biodiversity calculation as part of the standard information required for those applications. This will need to use the DEFRA 2.0 biodiversity metric. This will include some specific proxy habitats used for the following Cornish habitat types:

  • Cornish hedges
  • metalliferous mine sites
  • china clay quarries

The requirement will be that all developments will provide at least a 10% net gain for biodiversity.

How does it work?

  1. When considering development sites, there will need to be an assessment of net losses and gains in biodiversity. Reports on net gains and any losses will be submitted alongside existing environmental reporting and assessments using information that would normally be collected for the purposes of EIA or ecology surveys;
  2. Each application will be required to complete a standard biodiversity metric sheet with habitat information gained from the site assessment and landscape plans. This will be completed by a suitably qualified ecologist;
  3. Each development proposal will need to consider how a mix of preservation, creation and restoration of habitat on-site will help achieve biodiversity net gain within the site boundary and include this.
  4. Any planning permission granted will then provide a mechanism via planning conditions to secure the protection, enhancement and provision of habitat through the development as described in the net gain proposal.  It is anticipated from DEFRA updates that the statutory period for the monitoring of Net Gain will be 30 years from the commencement date of the proposal.

What if net gain cannot be achieved on site?

National and local policy expects the gain to be provided on site. However in the exceptional circumstance where off-site compensation is required, the metric provides the right information to discuss off-site compensation.

As part of planning permission, developers would sign-up to predictable condition or payment by planning obligation to secure biodiversity net gain off-site.

We are still working up proposals to allow this to happen. We will be publishing a Nature Recovery map. We will also publish a list of projects that indicates how payments can be invested. Further mechanisms for protection of that investment for the long-term using Conservation Covenants will be proposed and consulted on in due course.  

What other help is available?

The Biodiversity Guide already provides helpful guidance on measures that should provide a biodiversity net gain. It is currently being updated to assist applicants in further understanding Biodiversity Net Gain requirements.

The Cornwall Design Quality Guide includes further guidance on net gain. It also shows how it can become integral to the design of new development. A first draft of that guidance will be available in October 2019.  

Key contacts:

If you would like further information about the Biodiversity net gain requirement please contact:

Planning Policy:

Email the planning policy team:

0300 1234 151


Email the ecology team:

0300 1234 202