National Rarity and Scarcity Statuses, Reviews and Databases | Invertebrates in Freshwater

Important Invertebrate Habitats | Genetically Modified Crops | Climate Change

Standardised Survey Sampling | Freshwater Site Sampling

Site Quality Scores and Site Rarity Scores

Site quality estimates using invertebrates for EIAs and other planning procedures are based on national rarity and scarcity statuses emanating from the Joint Nature Conservation Committee. These statuses have been published in a number of reviews. The majority of the data on which the reviews were based was generated before 1990, using non-standardised insect collecting techniques.

Since the advent of environmental entomology and as a result of EIAs, considerable amounts of new distribution data has been generated using standardised survey methods. Consequently most of the reviews are now considerably out of date. EMS has over 100 records for some beetle species deemed to be Nationally Scarce A and B. One major problem within these reviews is that the authors did not use the stated designation system consistently. In particular there has been the inaccurate designation of some rare beetle species as Nationally Scarce when they should have been given RDB status.

The results of these questionable reviews have been used in a number of databases in various approaches that have been applied to environmental monitoring in the UK, for example:

Invertebrate Site Register (ISR) - a database of 'good' invertebrate sites based on the number of 'rare and scarce' species recorded. There are a number of problems with the ISR. There was no standardised data collation and some data was not accessed. The output tends to be partial and consequently the records in ISR need to be carefully assessed before they can be applied to environmental work, (see Eyre, 1998, in EMS Academic Publications).

RECORDER - there are problems associated with the use of this database with invertebrates. The conservation statuses are a repeat of the national review results, but there is no information about a considerable number of rare and scarce species. There has been no standardisation of data input into species accounts and considerable amounts of the habitat and distribution data is inaccurate. As a consequence this database should be used with care.

Biodiversity Action Plans (BAP) - Invertebrate conservation based on the concept of population size is generally inappropriate with invertebrates. One reason that some of the invertebrate species have BAPs is that they are difficult to find and are thus perceived to be rare. Other problems include such approaches as the grouping of several exposed riverine sediment (ERS) beetle species, where these species have differing habitat requirements ranging from dry cobbles to wet sand. Also, as standardised recording becomes 'normal practice', some species will become common and the predicted climate change involving increased temperatures is likely to have a considerable impact on invertebrate distributions and abundances. These factors may invalidate BAPs, (see Eyre et al., 2000, in EMS Academic Publications).

'Critical Species' - the use of Nationally Rare and Scarce invertebrate species, together with regionally rare species, as 'critical species' has been advanced by a number of workers, (e.g. Falk, S., 1996, Invertebrates and Local Authorities. In Environmental Monitoring, Surveillance and Conservation Using invertebrates, Eyre, M.D., ed., pp.63-66. EMS Publications, Newcastle Upon Tyne). This requires the filling in of a hand written form for each species, some of which are very common. Hand written notes about individual species are inappropriate, inadequate and unprofessional with regard to using invertebrates in an environmental context.

The advent of water quality work using the RIVPACs system by the Environment Agency has led to the perception that work on invertebrates in freshwater habitats has been standardised. For instance, standardised techniques for sampling freshwaters is difficult because of the considerable site variation. The 3 or 5 minute kick-sampling and stone turning method is fine if you have sufficient flow and stones. However, it has limited use in headwaters, mud and silt substrate streams and rivers and in pond and other static water sites. There is a need for the generation of a representative sample, which may require a considerable level of experience on the part of the sampler. The time taken to generate a sample depends on site substrate, vegetation structure and water flow or the lack of it.

There are also problems with the RIVPACs system. The original database did not contain lowland, silt substrate rivers that tend to be polluted, which has meant that the most badly affected rivers (e.g. the Ouseburn, Don and Skerne in north-east England) were not covered in the system. Additionally the analysis and statistical methods employed in the RIVPACs system are problematical. For example, one of the data inputs into the model, from acid water sites in Wales, is integral in predicting the taxa of base-rich rivers in north-east England, and as such the accuracy of the prediction is compromised.

One problem with the Biological Monitoring Working Party (BMWP) and Average Score per Taxon (ASPT) values is that pollution-tolerant taxa occur in clean water, with sites in lowland areas getting low scores (pollution indicative), even if unpolluted. One other aspect of the scheme is the assumption that formerly polluted, now clean, rivers will rapidly develop the macroinvertebrate fauna of clean rivers, once the pollution has been removed. This apparently, is not the case (Weatherley, N.S. & Omerod, S.J. 1992 The biological response of acidic streams to catchment liming compared to the changes predicted from stream chemistry. Journal of Environmental Management, 34, 105-115), and there is no work on the long-term effects.

There are some habitats that are very important for invertebrates but not for plants or birds. Exposed riverine sediments (ERS) and dead wood are the two most obvious. It is important to understand that ERS and dead wood are not one habitat but cover a large number of different habitats for different invertebrate groups.

Exposed riverine sediments form a gradient from dry boulders/cobbles to wet silt. Not only do the different combinations of particle size and substrate water influence the type of invertebrate assemblage present but also the influence of particle size and substrate water on different invertebrate groups is not the same. EMS has surveyed over 200 ERS sites and have found that there are more ground beetle assemblages than rove beetle assemblages over the same survey area and even fewer phytophagous beetle and spider assemblages. The effects on ERS habitats by river management affect these assemblages to different degrees and as a consequence there is no one effect on the invertebrates of ERS.

Dead wood contains a number of habitats, from under bark, through sapwood to heartwood. The types of fungi within dead wood affect the invertebrate assemblage present and, as with ERS, there is no one effect on the invertebrates of dead wood by woodland management practices.

A preliminary search of the literature on the effects of genetically modified (GM) crops on invertebrates has indicated that there has been little work on the potential effects of their planting on invertebrates in the landscape. As with most work on invertebrates, the limited investigations carried out seem to have been conducted at the laboratory or small plot scale. This work has tended to concentrate on the molecular and physiological effects of GM development. The death of Monarch butterflies after the ingestion of GM pollen was a physiological response. The effects of GM crops in the wider environment are far more difficult to investigate.

The major problem with investigations at the field, farm and landscape scale with GM crops and invertebrates is that the reasons for variation in the wider environment can rarely be identified and quantified. This means those differences in soil type and composition, vegetation architecture, aspect and microclimate, all factors likely to affect invertebrate species assemblages and numbers, tend to be ignored when comparing survey results. Researchers at Rothamsted are about to compare GM planted fields with more 'normal' fields using pitfall traps and suction sampling. Assigning conclusions concerning differences in invertebrate results between GM and normal fields will be meaningless if the effects of other environmental variables are not taken into account.

Climate change, especially in the form of a temperature shift, will have a profound effect on invertebrates. The fossil and subfossil record indicates that the response of invertebrates to large temperature changes (e.g. ice ages) is to alter distribution. There appears to be little evidence of evolutionary change.

There is already circumstantial evidence that an increase in temperature in the UK is affecting invertebrate distributions, particularly with bees and wasps (Edwards, R. ed. 1997, 1998 Aculeate Hymenoptera of Britain and Ireland, Parts 1 and 2. CEH, Monks Wood). It is likely that research on the distribution of invertebrate species will reflect the relatively crude measurement of air temperature and hence distributions may be relatively easily modelled. However, it will be very difficult, if not impossible, to predict the effect on invertebrate populations. It is likely that it will not even be possible to predict the abiotic effect of temperature change on populations in the landscape and there will be no way of detecting change brought about by biotic effects (e.g. predators, parasites and the distribution of host plants), each of which will be affected by climate change.

The lack of an ability to predict invertebrate species population fluctuation with climate change means that models based on population size tend to be of little use. There will need to be a considerably improved understanding of the effects of temperature rise on the distribution of invertebrate species before the effects on populations can be assessed.

There is an need to standardise the approach to using invertebrates in environmental quality and change assessments. This is especially important as far as sampling and site quality quantification are concerned.

Sampling - there needs to be a fundamental change from the various insect collecting techniques employed at present to standardised trapping methods. Using butterfly and sweep nets, beating trays and hand searching are not usually appropriate because these methods are weather-dependent, their application differs greatly between workers and they are not temporally reproducible. There are other problems associated with butterfly and dragonfly transects. In particular species recorded do not indicate that they are present on the site or in the water body present but what is flying past. Care has to be taken with the use of flying insects in environmental assessments although some, especially bees and wasps, can be useful.

The standardised survey method usually employed in environmental assessments is pitfall trapping. There has been a standard method (see Luff, 1996 in EMS Academic Publications) employed since 1985 and is used as the basis for a considerable number of academic publications. The method has been cited as the favoured procedure to be adopted in several Government publications and reports and is used by the Environment Agency to sample Exposed Riverine Sediments, (see Sykes, J.M. & Lane, A.M.J. eds 1996 The United Kingdom Environmental Change Network: Protocols for standard measurements at terrestrial sites. Natural Environment Research Council).

Standardised Pitfall Trapping Method - the traps are polypropylene pots, 7.5 cm diameter, 10cm deep. At each chosen sampling site, 5 (minimum) to 9 (recommended norm) or 10 (maximum) traps are installed, if possible in a straight line at 2m spacing or a 3 x 3 grid. Each trap is sunk in the ground just below the surface. In each trap about 1 cm. of neat commercial anti-freeze is added. Sites are visited every 2 weeks, if vandalism is a problem, or 4 weeks otherwise. They are emptied, the contents sieved and the traps replenished with anti-freeze. Normally the contents of the traps from each site are pooled on each trapping date. The contents are covered with anti-freeze and stored at room temperature. The samples are sorted on a white plastic tray into specimen tubes with 70% alcohol ready for identification.

One advantage of pitfall trapping is that it is not usually obvious. Other methods, such as pan traps (usually white and yellow) and Malaise traps, tend to be more obvious and prone to disturbance by both animals and humans. These other methods have not been used in standardised surveys in the UK, and there is little published work on their application.

This requires a pragmatic approach to generate a representative sample which may include kick sampling. Water beetles appear to be the only group to occur in the vast majority of water bodies and reliance on dragonflies should be avoided as they do not occur in a lot of aquatic habitat types and there are too few species in the UK.

Site Quality Scores (SQS) - given the problems with the national rarity and scarcity statuses, there is a need to use more up-to-date information. This should come from well-run national and local distribution schemes. National schemes are administered by the Biological Records Centre, and ones that can be applied are for water and ground beetles and for bees, wasps and ants. These groups can provide good data for the assessment of species rarity at national and regional scales.

Species Rarity Scores (SRS) are employed to generate Site Quality Scores (SQS), usually defined as a mean of the SRS's. This procedure has been applied at both a national and regional scale for water and ground beetles (see Foster, 1987; Eyre & Rushton, 1989; Foster & Eyre, 1992; Eyre, 1996; etc, in EMS Academic Publications), and has been applied to bees and wasps by Mike Archer (e.g. Archer, ME; Burn, JT 1995 The aculeate wasps and bees of Crow Wood, Finningley in Watsonian Yorkshire, British Journal of Entomology and Natural History, 8, 49-59). It was interesting that the initial rarity scores for species of bees and wasps were based on the RDB statuses. These have proved to be unreliable (Edwards, R. ed. 1997, 1998 Aculeate Hymenoptera of Britain and Ireland, Parts 1 and 2. CEH, Monks Wood), and are now based on the records in the BWARS scheme. It is therefore apparent that knowledge of the distribution, and therefore rarity, of species should be derived from a standardised approach involving recording schemes.