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Low Impact Bat Licence – Definitive Guide for 2023

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Low Impact Bat Licence – Get Your Project Back on Track

The low impact bat licence (formerly known as a CL21 licence, or “Bat Mitigation Class Licence”) is one option that’s available to you, if you discover that your development project will disturb bats or affect bat roosts present.

In simple terms, if you have bats on or near your development you’ll need special permission that permits activities that could lead to harm – be that destroying a bat roost or just handling a bat. This special permission takes the form a licence and you’ll need one even when you have planning permission, because planning consent does not in and of itself allow you to perform what are essentially illegal activities. 

Historically, securing a licence was a lengthy and complicated process and, in many ways, it still is. Though there is a sound justification for it being this way as it is vital that bats are managed sensitively throughout the development process. Detailed checks and exacting processes are one way of ensuring that this is the case. 

However, Natural England has recognised that there are certain situations where the conventional approach to managing certain bats is overly onerous and time-consuming. Consequently, they created the Low Impact Bat Class Licence to allow experienced bat surveyors to manage these developments with greater efficiency without causing undue harm to the local bat population. 

If your development project meets the criteria for being managed under this licence, you’ll enjoy a lower administrative burden. This is because bats and habitats can be managed in a group of up to three of each, rather than individually. You won’t have to wait for a physical document or deal with reams of paperwork either as your site must be registered under your bat consultant’s licence CL21 and they manage the process from start to finish. 

The net result of this is a faster resolution to your bat problem, so you can keep your scheme moving.

Can my scheme be managed under the “Class 21” Licence?

You’re probably thinking that a bat low impact licence sounds too good to pass up.

After all, what’s not to like about managing groups of bats and habitats with less paperwork in one smooth process? 

However, the real question is – does your scheme meet the certain criteria for a CL21 bat licence?

Whilst the criteria are clear, the answer isn’t always obvious. That said, looking at these criteria will give you a good idea as to whether or not a bat low impact licence is an option for your development. 

Context matters here – bats are a protected species with volumes of weighty legislation backed by severe, criminal penalties in place to ensure they and their habitats are respected. Both central and local governments are eager to reverse the general decline in bat populations (and biodiversity in general), and the CL21 bat licence wasn’t designed as a way to help developers avoid meeting their obligations to wildlife and the environment. 

Therefore, your scheme will only qualify for a low impact bat mitigation class licence if both the habitats on your site are of low importance and only a low number of relatively common species of bats are making use of them.

To indicate what this might look like in real life: 

A developer wants to convert an abandoned farm building into a warehouse. However, a single, male soprano pipistrelle has taken to using a small tree just outside the building as a feeding roost and a section of roof cavity as a night roost. In this instance, the habitats are fairly insignificant and only host to one male bat, so a bat low impact licence may be suitable. 

If, on the other hand, that same farm building had large maternity roosts present in the loft space or a hibernation roost in the basement, a low impact bat class licence would be a non-starter because these bat roosts are critical to the local bat population. Similarly, if twenty soprano pipistrelles were using various features in and around the building for roosting, a bat low impact licence wouldn’t be appropriate because of the sheer number of bats present.

You’ll notice that both of these overarching criteria are subjective, and situations are seldom as clear-cut as the examples above. Consequently, the final decision will rest with your specially trained and licenced bat surveyor as determining whether or not the licence applies is a decision that can only be made with informed professional judgement. 

With this in mind, it’s a good idea to discuss your development with a licenced bat surveyor as soon as possible so that you can get the bespoke advice you need and plan accordingly.

an ecologist conducting a bat survey

What is a Low Impact Bat Licence?

Only an experienced Bat Ecologist can use a low impact bat licence, and they have to be registered to do so. In all, about 220 professional ecologists are on the register and they each secure and use about 5 licences per year. Arbtech however, do more like 100.

Natural England has set a high bar for registration. This is because determining what constitutes a “small” bat roost present of low importance is perhaps the most complex professional judgement a licenced bat surveyor will have to make. Not only that, but the CL21 licence system is one based largely on trust. So, as getting it wrong could have catastrophic consequences for the local bat population, the only prudent thing to do is let only bat ecologists with weighty experience join the register. 

The licence itself has four annexes: three cover specific regions and one (Annex B) covers all counties in England. Your bat surveyor will likely make use of Annex B as this section allows them to disturb a broad range of bat species, specifically: 

  • Common pipistrelle bats
  • Soprano pipistrelle bats
  • Brown long-eared bats
  • Whiskered bats
  • Brandt’s bats
  • Daubenton’s bats
  • Natterer’s bats

Annex A is more limited in scope and only applies to a modest selection of counties in northern England. 

Annex C and D allow your bat ecologist to take action to disturb serotine and lesser horseshoe bats respectively. Again, like Annex A, Annex C and D each have a list of counties where they apply. There are also restrictions in regards to the roost type your surveyor can interfere with, and compensatory measures are mandatory if sufficient mitigation is not possible.

Whatever Annex your surveyor uses, the licence will cover up to but no more than three roosts present. Here, a bat roost present on the site is defined as a single bat species using a single structure for a single roost type. This means if you have more than three roosts or multiple bat species are using the same structure, your site won’t meet the certain criteria for a CL21 licence.

All of the bat roosts on your site must also be of what is regarded “low conservation status”. Bat roosts that are judged as low conservation status are limited to feeding roosts, night roosts, day roosts, and transitional/occasional roosts. So, if your site is host to maternity roosts, for example, you’re looking at needing an individual bat low impact class licence instead. 

Additionally, your site can only play host to a low number of bats. There is no hard and fast answer as to what constitutes a ‘small’ number of bats. Three common pipistrelles may well be an insignificant number in an area with an otherwise buoyant population. However, those same three bats could be a lynchpin of the local population elsewhere. Ultimately, it is entirely down to the Registered Consultant to draw on their professional experience and all the available evidence to make this determination.

One last point about the licence itself – it’s designed for short term works, usually up to about six months. If your scheme is likely to last longer, the chances of getting a low impact bat mitigation licence are slim to none.

How do I get my development to be managed under a CL21 Licence?

First of all, you need planning permission for your development, and all wildlife conditions must be discharged – including relevant bat survey work.

Beyond that, registering your site against a bat low impact class licence is a two-stage process; Only one of which will you have any direct involvement with (because the first step is simply the registration of the bat ecologist themselves). 

Once you’ve engaged the services of a Registered Consultant, it’s down to them to register your site before any works affecting bats or likely to disturb bats or roosts begin. This isn’t an overly long process – you’ll often hear of 15-day turnaround times. However, you probably won’t even have to wait that long because, in our experience, we’ve had CL21 licences issued in as little as three days. Regardless, it’s sensible to register in good time, if only to avoid unnecessary delays to your development works schedule.

The way a low impact bat class licence affects your development works schedule is, as you’d expect from something that’s specifically designed to streamline processes, relatively straightforward. 

Indeed, it allows the Registered Consultant a large degree of leeway when it comes to delegating authority to help your scheme run smoothly. For example, the Registered Consultant can appoint Accredited Agents to the licence to carry out works on their behalf (though they retain full responsibility for that survey work). These Accredited Agents themselves must have a current level 2 bat survey licence, and they must have held this licence for at least three years. So you can be sure that if your Registered Consultant does appoint an Accredited Agent, they will have the skills and experience necessary to safeguard you and your development. 

Additionally, they’re able to appoint assistants, and these can include contractors. A contractor hand stripping the roof of a loft conversion or a tree surgeon pruning a tree that contains a small feeding roost are just two examples of potential assistants under a CL21 licence. Critically, these assistants can not handle bats if they discover them in the course of their survey work. Only the Registered Consultant and/or Accredited Agents are allowed to do this.

Once you have your licence, there’s no requirement for post-construction monitoring (under Annex B), and one visit from your Registered Consultant or Accredited Agent is (usually) enough. 

As for mitigation and compensation, you technically don’t have to offer compensation on a low impact class licence. The only exception to this being the conditions relating to the protected species covered by Annexes C and D mentioned earlier. However, in practice, our Registered Consultants will offer one appropriate mitigation measure per species, per roost. Generally, we’ll try to keep any bat roosts in situ because this is both best for the bats and best for you as it avoids the need for costly, convoluted measures.

Do I need bat surveys to get registered under a Low Impact Bat Licence?

It’s important to note that a fair amount of evidence is needed to get a CL21 bat licence. Whilst the Registered Consultant does have a uniquely broad scope in which to exercise their professional judgement, there’s a little more to it. 

This is because Natural England needs to be sure that your scheme really is low risk in terms of the amount of harm that could befall the local bat population when you disturb bats and destroy their roosts. Absent evidence, even the most experienced bat surveyor cannot give them the assurances they need – not that they would even try.

Therefore, you’re going to need phase one and phase two bat surveys. These scoping bat surveys and bat emergence surveys give the Registered Consultant a base to survey work from. Of course, if you’re considering managing your scheme under a bat low impact licence, you’ll already have these as they would have formed an integral part of your successful planning application. 

If for whatever reason, you’ve experienced a delay between the last survey set and instructing a bat surveyor to consider registering your site against their CL21 licence, you could experience further holdups. Bat populations are, on the whole, small and fragile. As a consequence, significant changes can occur in a relatively short period of time. Your Registered Consultant and Natural England need up to date information about the bats on or near your site to determine whether or not granting a low impact bat licence is appropriate. In real terms, this means if more than three months have passed between the survey being completed and your application for a CL21 licence, a Material Changes Check will be required at the very least. 

Things potentially get a little more complicated if your most recent survey set wasn’t completed in the most recent survey season. Potentially you could be asked for a new set of bat surveys. Because some bat surveys can only be carried out between May and September, you may be looking at a significant roadblock if this is the case.

If you don’t ensure your application to manage your scheme under a low impact bat class licence is supported by sufficient robust, recent survey work, you run the risk of Natural England rejecting your application altogether. Were this to happen, it would be a needless waste of time and money that’s readily avoided by an early discussion about your options with an expert.

Speaking of experts…

Get a Bat Mitigation Class Licence for Your Scheme

If you think your scheme could benefit from a low impact mitigation licence, talk to us.

Our senior bat surveyors are registered with Natural England to use the Low Impact Bat Class Licence to provide sensible, efficient, and proportionate mitigation for registered sites. 

Even though bat low impact licence has only been around for a few years, every senior member of our team has been solving developers’ bat problems for years, if not decades.

This means they’re equipped with the specialist knowledge needed to ensure that your CL21 licence application gets accepted by Natural England and work with you to propose straightforward mitigation that doesn’t cost the earth. 

Better yet, our people are supported by our unrivalled infrastructure that’s geared towards one thing – speed.

The last thing we want is for you to waste time and money on Material Changes Checks (or even a whole new set of bat surveys) because your Registered Consultant couldn’t move through the process quickly enough.

Once you get in touch with us, you’ll be able to speak to a Registered Consultant in a matter of hours, not days. 

If a Low Impact Mitigation Licence is right for you, they’ll get things moving straight away.

For a low impact bat licence, from experts you can trust, fast – choose Arbtech.

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