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PRA Appendix

Preliminary Roost Assessment Methodology and Appendix Supplement (2024)

The aim of this supplementary document is to provide the supporting survey methodology, relevant legislation and bibliography used for the creation of the main Preliminary Roost Assessment (PRA) report.

The intention is to enable the main report to be as easy as possible to read, to help with understanding the conclusions, impacts, and recommendations made.

Scope of the Report

The PRA report describes the trees/building/structure’s roost potential at the site, evaluates habitats within the survey area in the context of the wider environment and describes the suitability of those habitats for supporting bats for foraging or commuting. It identifies possible impacts on bats as a result of the proposed development and summarises the requirements for further surveys and mitigation measures to inform subsequent licences or mitigation proposals, achieve planning or other statutory consent and comply with wildlife legislation.

Survey Methodology

To achieve this, the following steps have been taken:

A desk study has been carried out.

Desk Study

The desk study undertaken included a review of statutory designated sites that support bats, and notable habitats and granted European Protected Species Licence (EPSL) of bats held on magic.gov.uk database. An assessment of the surrounding landscape structure was also completed using aerial images from Google Earth and OS maps.

Additionally, to conform to best practice guidelines biological records data (BRD) within a suitable radius of the site may need to be obtained from the local biological records centre. If obtained, these are analysed and summarised in the conclusions and recommendations part of the report where relevant.

BRD will be required when bat roosts are confirmed at the site, either during the PRA stage or during the following surveys.

The data search is confidential information that is not suitable for public release and has been analysed and summarised for presentation in this report. They can be provided on request by the LPA.

The desk study methodology as outlined here has been carried out, and any relevant findings regarding sites, habitats or species will be incorporated into the conclusions and recommendations section of this report for ease of reading.

Field survey

A field survey has been undertaken to record baseline information on the trees/buildings/structures on the site and surrounding area including habitat and their suitability to support bats roosting, foraging or commuting.

Preliminary Roost Assessment.

The methodology for the PRA is based on the best practice publication of Collins, J. (2023). Bat Surveys for Professional Ecologists —Good Practice Guidelines, 4th edition, Bat Conservation Trust, London. Tree/building/structures are mapped and classified on their roosting potential.

Mapping includes details of the location of roosting features identified and any evidence found during the survey.  It will also include the position of surveyors if follow-up surveys are required. Target notes provide supplementary information if required.

While a search for evidence will be undertaken, it should be noted that not all bat species will leave direct evidence within a structure to confirm presence- due to the biology of certain species and their observed roosting behaviours.

Where no direct evidence of bat roosting is discovered, the assessment takes into consideration the findings of the desk study, the habitat conditions on site and in the context of the surrounding landscape, and the quality and number of features seen that can support roosting bats. The suitability to support roosting bats is ranked on a scale of none-high, and the appropriate amount of follow-up presence/absence surveys are recommended to prove presence or absence.

The roost potential has been graded for the tree/building/structure- including where no roosts have been confirmed.

Building/structure roosting features can be described in accordance with table 4.1 of the 2023 bat guidelines:

Tree roosting features can be described in accordance with table 6.2 of the 2023 bat guidelines:

Potential impacts on any identified roost or roost features, as a result of the proposed development, have been identified.

Recommendations for further surveys and mitigation have been made based on the above points and based on tables 7.1 and 7.2 of the bat survey guidance.

Opportunities for the enhancement of the site for bats have been set out- where no further surveys are required.

A survey plan and location map are presented in the report, along with a proposal plan (where available).


It should be noted that whilst every effort has been made to describe the roost potential or find any evidence of roosting bats within the structure/building, and evaluate these features, this report does not provide a complete characterisation of the site.

This assessment provides a preliminary view of the likelihood of bats being present. This is based on the suitability of the roosting features on the site and supporting habitat in the wider landscape, the ecology and biology of species as currently understood, and the known distribution of species as recovered during the searches of historical biological records.

Any limitations specific to the survey (e.g. access to the site or inside buildings, biotic or abiotic factors (e.g., wasps, asbestos) visibility, safety, or adverse weather) are discussed in the report in the conclusions, impacts and recommendations table, and given the appropriate weighting.

Follow-up surveys, such as presence or absence surveys, also known as Bat Emergence and Re-entry surveys (BERs), may be required in order to confirm presence or absence and would be expected by local planning authorities before permission is granted.


  • Bat Tree Habitat Key. (2018). Bat Roosts in Trees: A Guide to Identification and Assessment for Tree-Care and Ecology Professionals. Pelagic Publishing Ltd.Chartered Institute of Ecology and Environmental Management (2020). Guidelines for Accessing, Using and Sharing Biodiversity Data in the UK. 2nd Edition. Chartered Institute of Ecology and Environmental Management, Winchester.
  • Chartered Institute of Ecology and Environmental Management (2017). Guidelines on Ecological Report Writing. Chartered Institute of Ecology and Environmental Management, Winchester.
  • Collins, J. (2023). Bat Surveys for Professional Ecologists —Good Practice Guidelines, 4th edition, Bat Conservation Trust, London.
  • Garland, L. & Markham, S. (2008) Is Important Bat Foraging and Commuting Habitat Legally Protected? http://biodiversitybydesign.co.uk/cmsAdmin/uploads/protection-for-bat-habitat-sep-2007.pdf
  • Institution of Lighting Professionals (2023). Guidance Note GN08/23 Bats and Artificial Lighting at Night. Bats and the Built Environment Series Publication.
  • JNCC (2004). Bat Workers Manual, 3rd Edition. http://jncc.detra.gov.uk/page-2861
  • Magic Database. http://www.magic.gov.uk/MagicMap.aspx
  • Reason, P.F. and Wray, S. (2023). UK Bat Mitigation Guidelines: a guide to impact assessment, mitigation and compensation for developments affecting bats. Chartered Institute of Ecology and Environmental Management, Ampfield
  • Natural England Designated Sites View. https://designatedsites.naturalengland.org.uk/SiteSearch.aspx
  • National Planning Policy Framework (2023). https://www.gov.uk/government/publications/national-planning-policy-framework
  • Wray, S., Wells, D., Long, E., Mitchell-Jones, T (2010) Valuing Bats in Ecological Impact Assessment. IEEM In-Practice. Number 70 (December 2010). Pp. 23-25.

Relevant Legislation and Planning Policy

National and European Legislation Afforded to Species

The Conservation of Habitats and Species Regulations 2017 (as amended)

The Conservation of Habitats and Species Regulations 2017 (as amended) aims to promote the maintenance of biodiversity by requiring the Secretary of State to take measures to maintain or restore wild species listed within the Regulations at a favourable conservation status.

The Regulations make it an offence (subject to exceptions) to deliberately capture, kill, disturb, or trade in the animals listed in Schedule 2.

However, these actions can be made lawful through the granting of licenses by the appropriate authorities. Licenses may be granted for a number of purposes (such as science and education, conservation, preserving public health and safety), but only after the appropriate authority is satisfied that there are no satisfactory alternatives and that such actions will have no detrimental effect on wild population of the species concerned.

The Wildlife and Countryside Act (WCA) 1981 (as amended)

The Wildlife and Countryside Act (WCA) 1981 (as amended) implements the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention 1979, implemented 1982) and implements the species protection requirements of EC Birds Directive 2009/147 /EC on the conservation of wild birds in Great Britain (the birds Directive). The WCA 1981 has been subject to a number of amendments, the most important of which are through the Countryside and Rights of Way (CRoW) Act (2000).

Other legislative Acts affording protection to wildlife and their habitats include:

Natural Environment & Rural Communities (NERC) Act 2006

Wild Mammals (Protection) Act 1996


All species are fully protected by Habitats Regulations 2010 as they are listed on Schedule 2. Regulation 41 prohibits:

  • Deliberate killing, injuring or capturing of Schedule 2 species (e.g. All bats)
  • Harass a bat or a group of bats (Scotland)

Deliberate disturbance of bat species in such a way as:

  • To impair their ability to survive, breed, or reproduce, or to rear or nurture young;
  • To impair their ability to hibernate or migrate
  • To affect significantly the local distribution or abundance of the species
  • Damage or destruction of a breeding site or resting place – even if bats are not occupying it at the time.

Bats are afforded the following additional protection through the WCA as they are included on Schedule 5:

  • Intentional or reckless disturbance (at any level)
  • Intentional or reckless obstruction of access to any place of shelter or protection
  • Possess or advertise/see/exchange a bat of a species found in the wild in the EU (dead or alive) or any part of a bat

Effects on development works:

A European Protected Species Licence (EPSL) issued by the relevant countryside agency (i.e. Natural England, Natural Resources Wales, Scottish Natural Heritage) will be required for works are likely to affect a bat roost or an operation which are likely to result in an illegal level of disturbance to the species will require an EPSM licence. The licence is to allow derogation from the legislation through the application of appropriate mitigation measures and monitoring.


National Planning Policy Framework 2021

The National Planning Policy Framework promotes sustainable development. The Framework specifies the need for protection of designated sites and priority habitats and species. An emphasis is also made on the need for ecological infrastructure through protection, restoration and re-creation. The protection and recovery of priority species (considered likely to be those listed as species of principal importance under Section 41 of the Natural Environment and Rural Communities (NERC) Act 2006) is also listed as a requirement of planning policy.

In determining a planning application, planning authorities should aim to conserve and enhance biodiversity by ensuring that: designated sites are protected from harm; there is appropriate mitigation or compensation where significant harm cannot be avoided; measurable gains in biodiversity in and around developments are incorporated; and planning permission is refused for development resulting in the loss or deterioration of irreplaceable habitats including aged or veteran trees and also ancient woodland.

The Natural Environment and Rural Communities Act 2006 and the Biodiversity Duty

Section 40 of the Natural Environment and Rural Communities (NERC) Act 2006, requires all public bodies to have regard to biodiversity conservation when carrying out their functions. This is commonly referred to as the ‘biodiversity duty’.

Section 41 of the Act requires the Secretary of State to publish a list of habitats and species which are of ‘principal importance for the conservation of biodiversity’. This list is intended to assist decision makers such as public bodies in implementing their duty under Section 40 of the Act. Under the Act these habitats and species are regarded as a material consideration in determining planning applications. A developer must show that their protection has been adequately addressed within a development proposal.

European Protected Species Policies

In December 2016 Natural England officially introduced the four licensing policies throughout England. The four policies seek to achieve better outcomes for European Protected Species (EPS) and reduce unnecessary costs, delays and uncertainty that can be inherent in the current standard EPS licensing system. The policies are summarised as follows:

Policy 1; provides greater flexibility in exclusion and relocation activities, where there is investment in habitat provision;

Policy 2; provides greater flexibility in the location of compensatory habitat;

Policy 3; provides greater flexibility on exclusion measures where this will allow EPS to use temporary habitat; and,

Policy 4; provides a reduced survey effort in circumstances where the impacts of development can be confidently predicted.

The four policies have been designed to have a net benefit for EPS by improving populations overall and not just protecting individuals within development sites. Most notably Natural England now recognises that the Habitats Regulations legal framework now applies to ‘local populations’ of EPS and not individuals/site populations.

Limitations and Copyright

Arbtech Consulting Limited has prepared this report for the sole use of the above-named client or their agents in accordance with our General Terms and Conditions, under which our services are performed. It is expressly stated that no other warranty, expressed or implied, is made as to the professional advice included in this report or any other services provided by us. This report may not be relied upon by any other party without the prior and express written agreement of Arbtech Consulting Limited. The assessments made assume that the sites and facilities will continue to be used for their current purpose without significant change. The conclusions and recommendations contained in this report are based upon information provided by third parties. Information obtained from third parties has not been independently verified by Arbtech Consulting Limited.

© This report is the copyright of Arbtech Consulting Limited. Any unauthorised reproduction or usage by any person other than the addressee is strictly prohibited.


This assessment has been designed to meet:

Collins, J. (2023). Bat Surveys for Professional Ecologists —Good Practice Guidelines, 4th edition, Bat Conservation Trust, London; and
British Standard 42020 (2013) ‘Biodiversity – Code of Practice for Planning and Development’.


The work involved in preparing and implementing all ecological surveys, impact assessments and measures for avoidance, mitigation, compensation and enhancement should be proportionate to the predicted degree of risk to bats and to the nature and scale of the proposed development. Consequently, the decision-maker should only request supporting information and conservation measures that are relevant, necessary and material to the application in question. Similarly, the decision-maker and their consultees should ensure that any comments and advice made over an application are also proportionate.

This approach is enshrined in Government planning guidance, for example, the National Planning Policy Framework for England 2023. The desk studies and field surveys undertaken to provide a Preliminary Roost Assessment (PRA) might in some cases be all that is necessary. (BS 42020, 2013)

In consequence of the scale and intensity of the proposed development, showing no impacts on any bats, roost or roost features identified through both the site survey and search of local biological records, and the passive-interface with the mitigation hierarchy, this plan-led report is considered adequate and proportionate. It communicates all relevant information necessary to determine a planning application or support the recommendations for further surveys.

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