There are over 30,000 species (terrestrial and freshwater) of invertebrate in Britain. Many of these are in decline due to their sensitivity to environmental change and their inability to disperse quickly into new sites. Consequently invertebrate diversity can be used as a tool to assess the habitat quality of a site or the success of a prescribed management plan.
Survey Types & Timing
Invertebrate survey techniques vary enormously due to the vast number of invertebrate groups present and are often highly specific to the proposed site.
Terrestrial invertebrates can be surveyed using the following methods:
- Direct observation
- Hand searching
- Sieving of leaf litter
- Extraction of insects from leaf litter using extractors or water funnels
- Beating of woody vegetation
Specimens are either identified in the field and released or preserved for in-house identification.
Butterfly surveys are carried out by walking a set number of pre-determined transects using the method set out by the Butterfly Monitoring Scheme (BMS). During a butterfly survey records are made of the numbers of each butterfly species seen 2.5m either side and 5m in front of the surveyor. Transects should be walked at a steady pace and in weather suitable for butterfly activity. Several visits are required for butterfly surveys in order to provide an accurate representation of butterfly biodiversity..
A variety of survey methods can be used to assess freshwater habitats such as lakes, ponds, streams and rivers (depending on the accessibility of the water body to the surveyor). Standard survey methods of shallow water bodies are often based on protocols used for national biological water quality monitoring; these entail the use of a pond net to sweep, or a “kick sample” of, the aquatic habitats present.
Legislation & Planning
Many British invertebrates are protected under the Wildlife and Countryside Act (1981) (as amended). Species listed under Schedule 5 may be protected under one, some or all of the following parts of Section 9:
- possession or control (live or dead animal, part or derivative)
- intentional killing, injuring or taking
- damage to, destruction of, obstruction of access to any structure or place used by a scheduled animal for shelter or protection
- disturbance of animal occupying such a structure or place
- selling, offering for sale, possessing or transporting for the purpose of sale (live or dead animal, part or derivative)
- advertising for buying or selling live or dead animal, part or derivative
The Natural Environment and Rural Communities Act (2006) also lists around 400 invertebrate species that are ‘Species of Principle Importance’ under Section 41. Section 40 of the same Act requires every public body in the exercising of its functions (in relation to Section 41 species) to ‘have regard, so far as is consistent with the proper exercise of those functions, to the purpose of conserving biodiversity’. This makes the listed invertebrates a material consideration in the planning process, requiring a detailed ecological survey before planning permission can be granted.
Survey licences are not usually required to undertake general invertebrate surveys unless the survey is targeting species which are fully protected.
The Next Step
All efforts should be made to protect, conserve and, where feasible, enhance important invertebrate habitats within the proposed development site. Where this is not possible, suitable replacement habitats are likely to be required as part of landscaping proposals. Where works are to affect water bodies the Environment Agency may need to be consulted.