What is an ecological assessment and when is it needed?

Last updated: 2 July 2025

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 therefore 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.  

The Department of Agriculture, Environment and Rural Affairs (DAERA) has produced advice for the development of land that may affect natural heritage interests. This advice sets out what applicants must do to meet legislative and policy requirements in respect of protected species.   

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. 

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. Northern Ireland’s sites with environmental designations can be found on the Department of Agriculture, Environment and Rural Affairs (DAERA) interactive map here. Local non-statutory designated wildlife sites such as Sites of Local Nature Conservation Importance (SLNCI) are available to view in the LPA’s Local Development Plan.  

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. 

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 eg, by amending the design, preparing a mitigation plan or a compensation proposal.  

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.  

Unlike the EcIA process, which can be applied to any size of 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.  

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). 

• 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 from development guide (link in Find out more section below). 

• 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 (see this DAERA advice for more information). 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 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.  

Government guidance – Protected species  

Chartered Institute of Ecology and Environmental Management (CIEEM) – Guidelines for Preliminary Ecological Appraisal 

Chartered Institute of Ecology and Environmental Management (CIEEM) – Guidelines for Ecological Impact Assessment in the UK and Ireland 

CIEEM Guide to Ecological Surveys and Their Purpose 

Buglife Guide to Policy & Legislation Protecting Wildlife 

An overview of Environmental Impact Assessment

How do the Habitats Regulations protect our most important wildlife sites?

How to record wildlife: an action you can take to protect nature

How to assess the importance of a site under threat from development