Preliminary Ground Level Tree Roost Assessment (PGLTRA)
The Preliminary Ground Level Tree Roost Assessment (PGLTRA) is normally the first assessment undertaken on a tree to determine if bats and their roosts are ‘reasonably likely’ to be impacted by a proposed development.
The PGLTRA has three main purposes:
- To categorise a tree for its suitability to be used as a roosting place for bats
- Record any evidence of bats that may be present
- Make recommendation on the surveys required to determine the presence/likely absence of bats or characterise the bat roost that has been recorded (see dusk emergence dawn re-entry survey
PGLTRAs are normally undertaken at the planning stage of a development and they are commonly requested by Local Planning Authorities to support planning applications.
Permitted developments not requiring planning permission may also require a PGLTRA for bats to be undertaken in order to demonstrate that appropriate care has been taken to avoid impacts to bats and their roosts before the commencement of a project.
Searching for signs of bats
A PGLTRA consists of an external ground level search of a tree using binoculars and high powered torches to look for potential roosting features (PRFs) for bats such as a crack, crevices, cavities and holes.
During the PGLTRA, signs of bats such as bat droppings, urine splashes and feeding remains as well as bat specimens (live and dead) are searched for – although this is often limited to PRFs reachable from ground level which can be inspected with an endoscope.
What you need to know about a PGLTRA
Our approach
At Arun we regularly undertake PGLTRAs for bats as part of planning applications, and for statutory undertakers of permitted developments. Our PGLTRA for bats follow Bat Conservation Trust best practice guidelines and CIEEM competency guidelines.
We have in-house Bat Licenced Ecologists who are experts in their field to ensure accurate and efficient data collectinon.
Classifying a tree for roosting potential
The age, condition, proximity to certain habitat (such as woodland or waterbodies) and geographic location are key factors that define the term ‘reasonably likely’ in the context of bats being present and the suitability category assigned to the tree.
There are five categories that can be assigned:
Where there is certainty the tree is not suitable for roosting bats.
A tree of sufficient size and age to contain potential roosting features (PRFs) but with none seen from the ground or features seen with only very limited roosting potential.
A tree with PRFs that due to their size, shelter, protection, conditions and surrounding habitats could be used by bats, but is unlikely to support roost types of high conservation importance.
A tree with PRFs that are suitable for use by larger numbers of bats and that could be used on a regular basis and potentially for longer periods of time by bats.
Where the presence of a bat roost has been confirmed.
When can a PGLTRA can be undertaken?
A PGLTRA can be undertaken at any time of the year. It can often be easier to spot PRFs during the winter months when there is less foliage.
It is important to note that while PGLTRA surveys are not time restricted, dusk emergence and dawn re-entry surveys to determine presence/absence can only take place between May-September (with certain criteria that need to be met in this period).
What next following a PRA?
While the PGLTRA surveys can be used to confirm the presence of bats, the PGLTRA alone is not deemed a proportionate survey effort to conclude the likely absence of bats, unless the tree is deemed to be of negligible suitability to support roosting bats.
Scenario 1: If the tree is classified as negligible then the PRA report can be used to submit with a planning application or as evidence of an assessment for any permitted developments.
Scenario 2: The most common scenario is that further surveys such as dusk emergence and dawn re-entry or bat hibernation surveys will be required to demonstrate that development proposals will not impact bats. Further surveys should be factored in at the earliest stage as they are time sensitive.
FAQs
A Preliminary Ground Level Tree Roost Assessment is not a time constrained survey and can be undertaken at any time of year. However, it is important to note that many of the additional surveys often recommended in PGLTRA reports to determine the presence/likely absence of, or to characterise a bat roost, are time constrained. Completing additional surveys at the correct time of year is likely to be required to secure planning permission and bat mitigation licences (such as a European Protected Species Licence).
Example: Undertaking a PRA survey in September may mean that additional bat surveys are required to demonstrate that a proportionate survey effort has been made and to determine the presence or likely absence of bats. If all dusk emergence and dawn re-entry surveys are completed after September, the survey effort may not be accepted by the Local Planning Authority or Natural England, as this does not provide the correct coverage of the bat survey season. In this scenario it would be better to wait until the following May to complete the surveys.
It may be possible to secure planning permission with just a Preliminary Ground Level Tree Roost Assessment survey if the tree is categorised as having negligible or low suitability for roosting bats during the survey.
If a tree has any potential roosting features present (categorised as moderate or high suitability), in almost all circumstances further presence/likely absence surveys for bats will be required by a local planning authority before they consider the likely impacts of any proposals on bats. In line with biodiversity and geological conservation: circular 06/ all recommended surveys should be completed prior to submitting a planning application and should not be conditions of planning.
At Arun Ecology we will provide you with a questionnaire prior to any survey on the information we require to complete the survey, predominantly focusing on land access and health and safety. As an insight we require the following information:
- Land parcel and building access
- Any tenants present have been informed of the survey
- Any other hazards that might be present at the site (such as livestock or plant activity)
Typically a Preliminary Ground Level Tree Roost Assessment survey is accepted by a local planning authority for 12 months.
If the condition of a tree changes (for example following a storm) we would recommend updating the PGLTRA as soon as possible, as the trees suitability for bats may have changed. As such, this could help to remove the potential for an offence to be committed with respect to bats or create any unnecessary delays to your project.
Helping to address the ecological
and climate crisis
At Arun Ecology it’s not all just about driving business. We want to contribute to addressing the challenges of our time to ensure a prosperous future for the next generation.
So, as part of our service, each time you commission us we are committed to planting one tree within the UK, through our partnership with Creating Tomorrow’s Forests.
Watch this space to find out more about how we are contributing to nature recovery and tackling climate change.
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Whether you wish to request a quote or ask us a question, our friendly and experienced team will always be happy to advise and will endeavour to respond as quickly as possible.