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Thomson Ecology HandbookPreliminary Ecological Appraisal

TEH Index

Part 1: Legal frameworks

Part 2: Planning policy and other guidance

Part 3: Development and features of biodiversity importance

Part 4: Surveys and assessment

Part 5: Mitigation and enhancement

Part 6: Practical techniques

Preliminary Ecological Appraisal

A Preliminary Ecological Appraisal (PEA) is normally, as the name suggests, the first stage in any site assessment. It has three main elements: an ecological desk study; a habitat survey (typically an extended Phase 1 habitat survey); and a written assessment.

The PEA usually has several aims. These are: (i) to identify likely ecological constraints and features of biodiversity value present in and around the development site; (ii) to inform the design of the development such that impacts on features of biodiversity importance can be avoided or minimised; and (iii) to inform the scope of any necessary further ecological surveys and assessments that are likely to be required as part of the planning application process.

Where the preliminary ecological appraisal identifies specific issues such as the likely presence of protected species, or priority species, further surveys are likely to be recommended. These surveys provide information on which species are present, facilitating a more detailed assessment of the legal and planning policy issues and the potential impacts of the development on particular species.

Ecological desk study

The basic task for an ecological desk study is to gather together any existing data on designated sites, habitats and species of conservation concern from within and around the development site. Nowadays, there are on-line sources of information as well as that held by biological records centres and published in books and local planning documents.

The desk study can provide valuable information on the likely ecological issues that will be encountered during the development process and is a relatively inexpensive exercise to undertake. However, much of the data obtained through desk studies will be incidental records provided by the general public or volunteers, rather than the result of any systematic survey. Therefore, the desk study on its own is unlikely to provide sufficient information to complete the ecological assessment. Therefore it is usually undertaken as one element of a Preliminary Ecological Appraisal.

Extended Phase 1 habitat survey

The extended Phase 1 habitat survey provides a map of the habitats present on the site and a description of each habitat, including a plant species list. Each habitat is also assessed for its potential to support protected and priority species. Species of fauna observed during the survey are also recorded.

Phase 1 habitat surveys can be conducted all year round; however, the optimum time for undertaking the survey would be between April and September. If the survey is undertaken outside this period, it is quite likely that a follow-up botanical survey will be required.

Although it is the most widely used in Britain, the Phase 1 habitat classification system is not the only classification system that can be used for the PEA. An alternative is the Integrated Habitat Surveys (IHS) system developed by Somerset Environmental Records Centre. In Ireland, the classification system developed by Fossit (A Guide to Habitats in Ireland (Fossitt, 2000)) should be used.


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