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What is an ecological assessment and when is it needed?

Learn about what types of ecological assessments are required under the planning system.

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Last updated: 2 July 2025

When is an ecological assessment required?

Wildlife and the habitats they depend on can be affected by all types and scales of development and land use change. All development proposals must be assessed for their potential impact on species and habitats, regardless of their size. However, not all proposals will require an ecological assessment to be carried out. Ecological assessments are only sought when there is a reasonable risk of a protected species or habitat being present on the development site. 

Local planning authorities (LPAs) often require a ‘biodiversity checklist’ to be completed and submitted with most planning applications, which helps applicants to assess the likelihood of their site supporting protected species, and whether the impact of their development would trigger the need for an ecological assessment.  

Some LPAs also have development criteria and indicative thresholds to help applicants understand when an ecological assessment might be required.  

Certain types and locations of development sites will be more likely to support protected species, eg buildings that contain features that are suitable for bats, large gardens in suburban/rural areas which can provide habitats for breeding birds, badgers and reptiles, or sites located close to areas of ecological interest (eg a locally designated wildlife site or statutory designated sites of national or international importance). 

For statutory wildlife sites protected by law, off-site or ‘indirect’ impacts of a development must be considered. For example, this could be hydrological changes to a wetland site or increased recreational impacts as a result of the proposed development. 

How can I find out if a site is protected?

The planning application and ecological reports should mention if there are protected sites within the development site or nearby. To check, contact your Local Environmental Record Centre (sometimes called biological or biodiversity record centres) or your local Wildlife Trust as they usually have details of locally (non-statutory) designated wildlife sites. Statutory designated sites can be found on Defra’s Magic Map

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LPAs have a statutory duty to consider biodiversity when assessing planning applications. You can check that biodiversity has been considered properly by looking out for certain documents on the LPA’s online planning register using the planning application reference number.  

For small-scale development proposals check to see whether a biodiversity checklist or a preliminary protected species assessment has been completed by the applicant. For larger schemes look out for a section on ecology in a planning statement or a separate ecological report.

The Planning Officer’s report should include their own assessment of the ecological impacts of the planning application. These documents should be publicly available so contact your LPA if you can’t find them on their website.  

What types of ecological assessment are required?

Phase 1 Survey/Preliminary Ecological Assessment

For development proposals that have the potential to impact on protected species or priority habitats, a Phase 1 Survey, also known as a Preliminary Ecological Assessment (PEA), will need to be submitted to the LPA with the planning application. A Phase 1 Survey/PEA is undertaken by a qualified ecologist (ideally a member of the Chartered Institute of Ecology and Environmental Management) and involves a desk study and usually a ‘walkover’ survey. Its purpose is to identify what habitats are present on the site and whether any protected species might be supported there. The desk study should also identify the presence of any statutory or non-statutory designated wildlife sites or other wildlife interests within the vicinity that could be affected by the proposals. 

Detailed surveys (Phase 2 Surveys)

If a Phase 1 Survey/PEA identifies the likely presence of protected or valuable habitats or species within the development site that could be affected by the proposal, more detailed ‘Phase 2’ surveys will be required.  

These additional surveys must be completed and submitted to the LPA before the planning application can be determined. A qualified ecologist will provide advice on how to minimise the effects of a development on particular species or habitats e.g. by amending the design, preparing a mitigation plan or a compensation proposal.  

Ecological Impact Assessment

In certain cases, a Phase 1 Survey/PEA and detailed (Phase 2) surveys may not be enough to meet the overall ecological requirements of a development proposal. In these situations an Ecological Impact Assessment (EcIA) report may also be produced.  

Not to be confused with the broader, statutory Environmental Impact Assessment process, EcIA is a process of evaluating potential effects of a development on ecological interests specifically. The report should also include recommendations for measures to avoid, mitigate or (where the wildlife cannot be protected in situ) compensate for impacts to priority wildlife, as well as setting out any ecological enhancements.  

EcIA reports are provided to the LPA as part of the planning application in order to help the LPAs better understand the ecological issues when determining the application.  

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Although guidelines exist for ecologists undertaking Phase 1 and Phase 2 Surveys and Ecological Impact Assessments, there is no standard format for the process and the reports can be given various names such as ‘ecological report’, ‘wildlife assessment’ or ‘ecology appraisal’.  

Environmental Impact Assessment

Unlike the EcIA process, which can be applied to any size development, the statutory process of Environmental Impact Assessment (EIA) is reserved for larger developments or those that, because of their type or sensitive location, are likely to have more significant effects on the environment or important ecological interests such as statutory wildlife sites. 

EIA assesses the effects on a much wider range of environmental interests, including impacts on people as a result of changes to air quality, landscape and cultural heritage for example. Ecological impacts will be assessed alongside these other topics, with the ecological chapter of the EIA taking a similar approach to the EcIA process.  

Take a look at our EIA guide (link in Find out more section below) for further information on the process, including tips on what to look out for when reviewing an applicant’s EIA documents.  

Habitats Regulations Assessment

Where developments could affect one of the UK’s wildlife sites with the highest level of statutory protection – those being Special Protection Areas (SPAs) for birds, Special Areas of Conservation (SACs) for habitats and other species, and Ramsar Wetland Sites – a Habitats Regulations Assessment (potentially including a full ‘Appropriate Assessment’) is also required. 

This type of assessment specifically considers the potential impacts of the proposal on the designated interests of the SPA, SAC or Ramsar site, including any avoidance or mitigation measures necessary to ensure that the special interests of the site will not be harmed.  

You can find out more in our guide to Habitats Regulations Assessments (link in Find out more section below). 

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Where certain protected species could be affected, development will only be able to proceed with a licence granted by the relevant licencing authority e.g. Natural Resources Wales. Read more about wildlife licences here.  

LPAs are not allowed to determine planning applications until all the necessary ecological surveys have been submitted and any mitigation plans and wildlife licences have been agreed (or secured by a planning condition or planning obligation). 

Ecological assessments – what to look out for

  • Is anything missing? If a desktop study has been undertaken, make sure it contains records of the species you know are present on the site. Local Environmental Record Centres (LERCs), which are sometimes called biological or biodiversity record centres, are the go-to place for records, but they don’t necessarily hold all records. Remember that ‘absence of evidence is not evidence of absence,’ so a lack of records doesn’t necessarily mean a species isn’t present at a location. Find your nearest LERC here. For more information about accessing data, see our How to assess the importance of a site under threat guide from development (link in Find out more section below). 

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It is always important to submit your wildlife records to national databases (eg iRecord) or local recorders because these can provide part of the records for desktop studies undertaken to inform ecological assessments for development proposals. 

  • Is the survey methodology correct? Check that any surveys have been carried out at the correct times of the day/year for that particular species. Compare the findings with your own local knowledge and experiences of the development site. If you find any discrepancies between the submitted information and your own evidence, contact the LPA immediately to let the Planning Officer know.  

  • Are further surveys required? If a Phase 1 Survey/PEA identifies the likely presence of a protected species or habitat, further detailed surveys that focus on the impact of the proposal on that particular species must then be undertaken (also known as a Phase 2 Survey). For larger proposals, or those near to an area of ecological interest, a full impact assessment (EcIA) of the potential effects on the priority species present may be required. 

  • Is the survey data up to date? Ecological survey data (both field-based and desk-based) is only valid for a certain amount of time, potentially up to a maximum of three years, although this can vary for certain sites and species. When reviewing an ecological report submitted with a planning application, check the date that any surveys were completed and use this handy CIEEM guide to check how long the data is likely to be valid for.  

  • Has the ‘mitigation hierarchy’ been followed? National planning policy sets out an important principle that should be applied to all developments that could impact on wildlife, often described as the ‘mitigation hierarchy.’ This means that impacts on wildlife should first be avoided wherever possible, mitigated (reduced or minimised) where they cannot be avoided, and compensated (wildlife features replaced, usually off-site) as a last resort. If information on avoidance, mitigation and compensation measures is missing, or if you feel that the proposed measures aren’t good enough, make the Planning Officer aware of this as soon as possible. 

  • Are the avoidance, mitigation and compensation measures included in the actual planning proposal? Check that any recommendations in the ecological reports, that are needed to protect priority wildlife, are included as part of the planning proposals. If not, raise this with the Planning Officer to ensure that the necessary measures are secured by condition/planning obligation.  

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Regardless of whether an ecological assessment is required, all planning applications should include opportunities to promote wildlife gains through ecological enhancement in accordance with national and local planning policies.

Look out for this information when you’re reviewing planning applications in your local areas and highlight any additional opportunities for enhancements to the LPA (this can be on a ‘without prejudice’ basis if you are objecting to the application in question).  

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