How to treat irreplaceable habitat for biodiversity net gain

What irreplaceable habitat is

Irreplaceable habitat cannot be created, or it would take a very long time to restore its normal ecological function if impacted. This may be due to its: 

• age 

• uniqueness 

• species diversity 

• rarity 

Irreplaceable habitat includes some of England’s most ecologically valuable terrestrial and intertidal habitat.  For example: 

• ancient woodland 

• ancient and veteran trees 

• blanket bog 

• limestone pavements 

• coastal sand dunes 

• spartina saltmarsh swards 

• mediterranean saltmarsh scrub 

• lowland fens 

The Biodiversity Gain Requirements (Irreplaceable Habitat) Regulations 2024 sets out the list of irreplaceable habitat and descriptions.

Development on irreplaceable habitat 

You will only get planning permission or consent for development that results in loss of irreplaceable habitat in exceptional circumstances.

The 10% biodiversity gain objective applies differently where there is irreplaceable habitat on-site. This is because it would be impossible to restore, recreate or replace such habitat.

Instead, you need to minimise adverse impacts and agree a bespoke compensation strategy with the local planning authority (LPA), or with the relevant decision maker for NSIPs. 

If your proposed development will result in the loss or deterioration of any irreplaceable habitats, you should refer to relevant planning policy and guidance on irreplaceable habitats:

• national planning policy framework on irreplaceable habitat – for developments that require planning permission 

• the relevant national policy statement – for NSIPs

The guidance on this page only describes what you must do for the purposes of BNG.

Compensation rules for irreplaceable habitat 

Special compensation rules apply to irreplaceable habitat.  

You will need to agree a compensation strategy with the LPA or relevant NSIP decision maker.  

Compensation for irreplaceable habitat needs to be relative to the baseline habitat type. The LPA or relevant NSIP decision maker will agree compensation as part of the determination of the planning or development consent order application. This should be done on a case-by-case basis and informed by the statutory metric.  

Read more about compensation rules for irreplaceable habitats in the: 

• biodiversity net gain planning practice guidance – for developments that need planning permission 

• relevant biodiversity gain statement – for NSIPs

Statutory credits

Statutory biodiversity credits cannot be used as compensation for impacts to irreplaceable habitat.

What developers need to do 

1. Consider irreplaceable habitat from the start 

Think about irreplaceable habitat at the design and planning stage, and look at how to avoid any adverse impacts. 

Developments that need planning permission

At the planning application stage, you will need to satisfy the  minimum information requirements. 

You will need to provide: 

• a description of any irreplaceable habitat on site at the date of the planning application 

• a plan of existing irreplaceable habitat on site at the date of the planning application 

Your LPA may ask you for more information related to biodiversity net gain and wider planning policies designed to protect the environment.  

Find out more in the biodiversity net gain planning practice guidance.

Nationally significant infrastructure projects

For NSIPs, you will need to include the following information on irreplaceable habitat in the outline biodiversity gain plan: 

• a description of any irreplaceable habitat within the BNG boundary on the baseline date 

• a plan showing the location of any irreplaceable habitat within the BNG boundary on the baseline date

• a description of the steps you have taken, or will take, to avoid and minimise impacts on irreplaceable habitat 

• a compensation strategy for any impacts of the development resulting in loss or deterioration of the irreplaceable habitat, where necessary

Find out more in the relevant biodiversity gain statement.

2. Record irreplaceable habitat in your BNG calculation 

You must record all irreplaceable habitat on your site in the metric calculation tool, regardless of whether they will be affected by the proposed development. 

This means any irreplaceable habitat within: 

• the red line boundary – for developments that need planning permission 

• the BNG boundary – for NSIPs

When there are adverse impacts to irreplaceable habitat   

Impacts to irreplaceable habitat cannot be measured by the biodiversity metric and are automatically removed from the baseline calculation in the tool.   

Do not record any bespoke compensation action for losses of irreplaceable habitat within the enhancement or creation sheets of the biodiversity metric. 

Find out more in the statutory biodiversity metric user guide. 

When irreplaceable habitat is enhanced 

Where there are no losses or deterioration of irreplaceable habitat, you must record enhancements in the metric calculation tool and include them in the baseline calculations. 

Enhancement works may contribute towards the calculation of post-development biodiversity units. 

Enhancement works must be ecologically appropriate and not have any adverse impacts on irreplaceable habitat. You will need consent from the relevant authority if they are part of a protected site.

When the development site includes irreplaceable and non-irreplaceable habitat 

You must achieve at least 10% BNG  on non-irreplaceable habitat:

• on your development site – for developments that need planning permission 

• within the BNG boundary – for NSIPs

This is in addition to agreeing bespoke compensation for impacts on irreplaceable habitat, which cannot count towards your BNG requirement.  

3. After permission or consent

Developments that need planning permission

If planning permission has been granted, you will need to provide details in the biodiversity gain plan for the development.

This should include: 

• type, extent and condition of any irreplaceable habitat there is before development 

• any expected changes in irreplaceable habitat type, extent and condition as a result of development 

• actions taken to minimise adverse impacts to irreplaceable habitat 

• compensation plan, where required

Phased developments that need planning permission

Special arrangements apply for the treatment of irreplaceable habitat for phased development and permissions granted under section 73.

Nationally significant infrastructure projects

After consent is granted, your updated or phase plan must detail and justify any changes to the information in the outline biodiversity gain plan. This includes any changes to information on irreplaceable habitats.  

For example, you may need to update the compensation strategy after submission to reflect changes in anticipated impacts to the irreplaceable habitat, feedback from consultees, or new ecological survey data.