Within the planning application process, Local Planning Authorities will often require the consideration of the ecological value of a site, to inform any constraints to the development with reference to national and local planning policy, as well as the legislation afforded to habitats and species in the UK.

A Preliminary Ecological Appraisal (PEA) is a cost-effective tool used to provide a rapid assessment of ecological features actually or potentially present at a site, and outlines solutions to the potential constraints that ecology may represent to a project. Preliminary Ecological Appraisals (PEA) should be undertaken with reference to best practice guidelines from the Chartered Institute of Ecology and Environmental Management (CIEEM)[1].

A PEA comprises three main elements: a desk study, a Phase 1 Habitat Survey extended to consider protected species (termed an ‘Extended Phase 1 Habitat Survey’), and a report. The scope of a Preliminary Ecological Appraisal (PEA) is to:

  • Identify probable ecological constraints associated with a development project.
  • Identify proportionate actions required to avoid, mitigate or compensate for impacts on ecological features in accordance with the mitigation hierarchy.
  • Identify any habitat or protected species surveys that may be required to inform the above.
  • Identify any opportunities to deliver ecological enhancement.

Desk study

With reference to the British Standard ‘BS 42020:2013 Biodiversity – Code of Practice for Planning and Development’, a desk study should be carried out to inform ecological assessments for planning applications.

A desk study compiles historical data on designated sites for nature conservation, habitats and protected species at a site and within the relevant zone of influence for the development project.

In accordance with best practice guidelines[1], a desk study uses habitat and protected species data from multiple sources including publicly accessible government webpages, and where required the purchasing of desk study data from the relevant Local Environmental Records Centre.

Extended Phase 1 Habitat Survey

A Phase 1 Habitat survey comprises a site survey carried out by an ecologist. The Phase 1 Habitat Survey compiles a list of botanical species, using plant species occurrence and abundance to classify and map the various habitat types present on site. The survey is ‘extended’ to assess the potential use of the site by protected and/or priority species such as great crested newt, badger and bats.

An Extended Phase 1 Habitat Survey can be undertaken year-round; however, the optimal survey season is between April and September. Phase 1 Habitat Surveys undertaken over winter may need to be updated in summer where potentially complex habitats are present, however this is not common.


The accompanying report typically includes survey methodologies and results, and if applicable outlines solutions to ecological constraints with reference to legislation and planning policy or suggests further survey recommendations required to inform a full assessment. The report includes a Geographical Information System (GIS) generated map of habitats within the site.

Where a Preliminary Ecological Appraisal (PEA) does not require the need for further surveys to assess the ecological impact of a proposed development, with reference to best practice guidelines the resulting report is termed an Ecological Impact Assessment (EcIA)[2]. Where additional ecological surveys are required to assess the impacts of a proposed development, a Preliminary Ecological Appraisal Report (PEAR) is issued, containing recommended further work with reference to the applicable legislation and/or planning policy.

A valuation of the cost-effectiveness of undertaking further surveys is always made prior to their recommendation. For example, in many cases avoidance measures can be implemented during construction or the operational phases of a development, to negate the need for ecological surveys and associated time delays.


[1] CIEEM (2017). Guidelines for Preliminary Ecological Appraisal, Second Edition. Technical Guidance Series. Chartered Institute of Ecology and Environmental Management, Winchester.

[2] CIEEM (2017) Guidelines on Ecological Report Writing. Chartered Institute of Ecology and Environmental Management, Winchester.


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