Ecological survey is the umbrella term for the work an applicant commissions to show a planning authority what is on a site and what the development would do to it. In practice it is a preliminary appraisal first, then whatever species or habitat surveys that appraisal recommends.
What the authority is deciding
Whether the development would harm protected species or habitats, whether that harm can be avoided, mitigated or compensated, and whether the biodiversity requirements are met. The survey exists to answer those questions with evidence rather than assertion.
What a survey covers
The habitats on site and their condition, the species the habitats could support, evidence of protected species, and the features that matter: ponds, hedgerows, mature trees, watercourses and buildings. Adjacent land is considered where the works could reach it.
When ecology surveys for planning are required
When the local validation list says so, when the site or its surroundings suggest protected species, and increasingly as a matter of course for anything beyond householder scale in England because of the biodiversity requirements.
What it produces
A report the authority can rely on: what was found, when and how it was surveyed, what the constraints are, and what further survey or mitigation is recommended. A report that hedges everything satisfies nobody and usually generates a further request.
Questions people ask about ecological survey
What is an ecological survey?
A survey of a site's habitats and the protected species it could support, carried out by an ecologist and reported so a planning authority can determine an application.
Is an ecological survey for planning always needed?
No, but the threshold has fallen. Check the authority's validation list and ask an ecologist early, because a late request is what costs a season.
Who reads the report?
The case officer and, on anything significant, the authority's own or a county ecologist. Writing to what they expect is part of what you are buying.