Practical techniques: Invertebrates
UK and Ireland
Approximately 65% of all species on the planet are invertebrates. In the UK alone, there are 32,000 terrestrial and freshwater and 7,000 marine invertebrates. Ireland is less species rich but still supports approximately 16,000 invertebrate species, of which 1,500 are considered aquatic. Invertebrates are not only important in their own right, they are an essential food source for other fauna such as birds and bats and also have huge value to humans both economically and ecologically.
Protection and its implications
Sites with high interest for invertebrates are largely protected from damage through their inclusion within designated sites, including:
- Sites of Special Scientific Interest (SSSIs)
- Special Areas of Conservation (SACs)
- Areas of Special Scientific Interest (ASSIs)
- Natural Heritage Areas (NHAs)
- National Nature Reserves (NNRs)
- Local Nature Reserves LNRs)
- County Wildlife Sites (CWSs) or similar local designation
The protection of these sites is described earlier in this handbook. Outside of designated sites around three species in the UK (Britain) and one, additional species in Ireland are fully protected under regulations derived from the Habitats Directive, 50 species of invertebrate are at least partially protected under the Wildlife and Countryside Act 1981 (as amended), (excluding those only protected from sale); 13 species are afforded protection under schedules 5 and 7 under the Wildlife (Northern Ireland) Order 1985 (as amended). The habitats of the invertebrate species listed on Annex II of the Directive (12 of these species occur in the UK (Britain) and 8 in Ireland) also receive some protection under the regulations derived from the Environmental Liabilities Directive, even when they occur outside designated sites. They are mostly very rare and restricted to nature reserves and other designated sites. These invertebrate species are therefore unlikely to occur on development sites and their protection rarely has implications for development. Agreement would need to be reached with the appropriate statutory agency for any development that could affect these species and a licence may be required in some cases.
Approximately 400 invertebrate species are listed as priority species in England, approximately 200 species in Wales, approximately 200 species in Northern Ireland and approximately 300 species in Scotland. In addition, further species may be identified as priorities for action at a local level in the relevant Local Biodiversity Action Plans or on local Priority Lists. Note: The lists of species for each country include many of the same species.
Whilst these species are not necessarily strictly protected (several are protected by the legislation described above), government policy is that local planning authorities should consider these species when determining planning applications. Consideration of priority species would also be expected in the UK as part of the legal Biodiversity Duty. Again, most of these species are rare and confined to nature reserves and other designated sites and therefore not usually encountered by a developer.
Ecologists’ reports sometimes refer to other categories of invertebrate status, for example nationally rare, nationally scarce and locally rare. These categories do not necessarily mean that the invertebrate species is protected. However, it is good practice, especially for developments requiring an EIA, to consider the protection of these species on development sites. Nationally scarce and locally rare species can sometimes occur on development sites, especially brownfield sites. Particularly rich or diverse assemblages or communities of invertebrates are at least as important a consideration as rare or protected species. Assessments of the value of a site for inveretbrates therefore ususally also consider this aspect.
Protection of individual invertebrates and communities
Because of their size and the small scale of their habitats, it is usually impractical to try to mitigate against loss of individual invertebrates, or to manage receptor areas for single species. Mitigation or compensation for invertebrates is therefore generally habitat-based. By far the best option is to design the site layout to retain the best areas of invertebrate habitat and to protect populations of uncommon invertebrates in situ. If there is no scope to retain existing habitats then compensatory habitats that are carefully designed with invertebrates in mind can be created elsewhere. Ideally this would be in place before the existing habitat is lost so that there is always appropriate habitat present.
The capture and removal of invertebrate species from development sites is rarely required. However, it could be necessary if a strictly protected species is found on a development site. The methods employed to capture such invertebrates would very much depend on the species concerned and would require a licence from Natural England. The receptor site would need to provide exactly the right conditions for the species in order for translocation to be successful. Since the requirements of many of our invertebrates are poorly understood, this can be difficult to achieve. Translocations undertaken to date have therefore often met with failure, although there have been some notable successes.
Photo: Alistair Krzyzosiak, longhorn beetle
Maintaining invertebrate habitat
There are a variety of ways in which invertebrates can be accommodated within development sites and even small areas of semi-natural habitats can be beneficial. Replacement habitats can be created, although these may never be as valuable to invertebrates as the original habitats. Features which may benefit invertebrates include:
- Ponds, ditches, reed beds and other wetland habitats
- Woodland, hedgerows and native shrubs
- Open, sunny grassland that is rich in wild flowers
- Sandy banks
- Areas with poor soils and sparse vegetation, as found on some brownfield sites
- Log piles and other dead wood
- Invertebrate nesting and feeding boxes
Derelict sites in urban areas often support good invertebrate populations. The redevelopment of ‘brownfield’ sites can therefore have negative effects on invertebrates; an approach gaining popularity to mitigate the effects of development is the provision of green roofs. These can be designed to offer the same sort of sparse vegetation that is found on derelict sites and therefore offer some compensation for lost habitats. Whether habitats are retained or created, they will need to be managed appropriately to ensure that the invertebrate interest is maintained.
Invertebrate monitoring requires a skilled ecologist, using a variety of traps and nets to collect specimens. Groups of invertebrates can be used to measure habitat quality; for example, water quality is measured using diversity scores of aquatic invertebrates. Monitoring can be conducted several times a year to ensure that invertebrates that are active during different seasons are adequately surveyed. Alternative indicator species can be used to determine invertebrate abundance (for example, bats, insectivorous birds and mammals).
Timing of works
Due to the large diversity of invertebrates and their varied habitats, the timing of mitigation and monitoring works will depend on the species and nature of mitigation or monitoring proposed.
Kirby, P. (2001). Habitat Management for Invertebrates: A Practical Handbook. RSPB, Sandy.
Buglife has produced an extensive series of guides and publications for managing all types of priority habitats and various types of non-priority habitat and development sites for invertebrates.
Natural England (2015) Invertebrates: surveys and mitigation for development projects. https://www.gov.uk/guidance/protected-invertebrates-protection-surveys-and-licences