Biodiversity Net Gain

Biodiversity net gain (BNG) is an approach to the development and management of land that aims to leave biodiversity in a measurably better state than it was before development occurred. It will ensure habitats for wildlife are retained, enhanced and created through the development process.

Under the Environment Act 2021, all planning permissions, with a few exceptions, are required to deliver a minimum of 10% increase in the biodiversity net gain delivered compared to the pre-development baseline. BNG will be measured using Defra’s biodiversity metric and all net gains will need to be secured and monitored for at least 30 years.

These commitments are further developed in Policy LP16 of our new Joint Local Plan and in the Biodiversity Net Gain Interim Planning Guidance Note for Suffolk. More detailed guidance on BNG will also be set out in a new Biodiversity and Trees Supplementary Planning Document.

Our vision reflects the principles and proportionality of BNG as set out in Professor Sir John Lawton’s report, Making Space for Nature. The report’s main message was that we need to make our network of sites more, bigger, better and joined to protect and restore biodiversity. For us this means:

  • Creating new sites
  • Increasing the size of wildlife sites
  • Protecting what we have, while improving its quality with better management including through buffers for wildlife sites
  • Enhancing connection by creating new wildlife corridors or stepping stones;

Achieving net gain for biodiversity - guidance for developers

All developments, with a few exceptions, are required to achieve a minimum biodiversity net gain of 10%. This guidance for developers will explain:

  • What written information you need to submit with planning applications to assess net gain
  • What measures will be required if you can't achieve a 10% net gain for biodiversity onsite
  • How Net gain is demonstrated using the Defra’s biodiversity metric

For Householder Applications - please see section below.

Our requirements

We are seeking a minimum 10% net gain through the use of the Defra approved biodiversity metric, which in most cases, should be delivered on-site. Where this is not possible (and his needs to be agreed with us) it may involve off-site compensation.

We expect all applications to conform to this guidance to achieve consistency of information on which to carry out decision-making. If this guidance is not followed (the Defra biodiversity metric is not used), we still require all applications to demonstrate how they are achieving net gain in a measurable way. If more Net gain is being proposed this will be looked upon in a more favourable light.   

Biodiversity Metrics - what does it assess? 

Habitat Type: The habitats present on site determined by a competent person.
Habitat Size: The area of each habitat type present on site, compared to the habitat area proposed to be retained, enhanced or created. 
Distinctiveness: A score based on the type of habitat present.
Condition: A score based on the biodiversity value of the habitat relative to others of the same type. This is determined by condition criteria set out in the technical supplement.
Strategic Significance: A scored based on whether the location of the development and/or offsite work or the habitats present/created have been identified as significant for nature.

What information is required to assess net gain?

We will be using the information set out below as our interim position until the detailed government guidance from DEFRA is published. More information on their draft Biodiversity Gain Plan Template and Guidance for Developers.

It is already a requirement that an Ecological Impact Assessment (EcIA) is submitted with most types of planning applications. The exceptions are when dealing with householder applications or sites with very low value ecological features, in which case a written statement or Preliminary Ecological Appraisal may still be acceptable.

The EcIA (or BNG report and calculation tool) must demonstrate how the site has been assessed using the Defra’s biodiversity metric. This will demonstrate the baseline value of the site (before the development takes place) and its post-development value. Where we think the baseline value of the site has been affected negatively prior to assessment, we will require an assessment of the site using aerial photography, evidence or surveys on the condition before such an occurrence as at 30 January 2020. If there is any doubt of the Distinctiveness or Condition, it will be assumed that the highest likely value will apply.

Clear scaled maps will be required showing precisely where the individual biodiversity units (comprising for example habitats, hedgerows, watercourses and lines of trees) occur for both the Baseline and post-development scenarios. There should also be a section demonstrating why the condition score has been chosen, with reference to all scoring criteria from the associated Defra Technical Guidance habitat tables.

In most cases, the objective should always be to deliver a minimum of 10% net gain on-site and it is essential to appoint an Ecological Consultant at the earliest stage of design for the proposed development. We also recommend that the Ecological Consultant works closely with both the Landscape Architect and other experts to consider which options of the layout lead to the best possible outcome for achieving net gain on-site.

For those types of development which require a Design and Access Statement, we expect to see evidence of different layouts with their corresponding different Biodiversity Unit impact and an explanation why one option has been chosen over another. This is particular important if the option with the lowest impact on biodiversity has not been taken forward to the proposed layout stage.

The EcIA should also follows the Guidelines for Ecological impact as these explain the evidence needed that the following sequential tests in the Mitigation Hierarchy have been followed:

  • Avoidance: Seek options that avoid harm to ecological features (for example, by locating on an alternative site). 
  • Mitigation: Negative effects should be avoided or minimised through mitigation measures, either through the design of the project or subsequent measures that can be guaranteed – for example, through a condition or planning obligation. 
  • Compensation: Where there are significant residual negative ecological effects despite the mitigation proposed, these should be offset by appropriate compensatory measures. 
  • Enhancement: Seek to provide net benefits for biodiversity over and above requirements for avoidance, mitigation or compensation

What do we require when net gain cannot be provided on-site?

We want to encourage high quality biodiversity enhancements on-site. However, we acknowledge that there will be times where a 10% net gain cannot be delivered on-site. We are waiting for the Government to set out the details of how certain factors such as conservation covenants, biodiversity credits schemes and other mechanisms will be set up, regulated and managed so this must be considered as an interim position, pending the publication of further government regulations.

Householder Applications

The metric is not applicable to householder applications, therefore you will need to provide one or more from the following Biodiversity Checklist:

  • Integral bat boxes
  • Integral bird boxes/bricks: Rather than generalist bird boxes, these should be tailored to priority species such as House Sparrow, Starling, Swift and others. See here for list of Priority species
  • Integral bee bricks
  • Green roofs/walls or Brown/"Living" roofs: These should support diverse habitats, sedum is NOT considered appropriate as it is a monoculture. For more information, click the following link: Green Roof Code
  • Hedgehog friendly fencing. Please Note, this is only relevant for applications which are actually for fencing.