Although the beetle assemblages occurring on exposed banks of sand, mud, shingle, etc., alongside our rivers are generally composed of a characteristic suite of species, most of the individual species are not confined to these habitats. The juxtaposition of wet and dry open habitats on a range of sediment types means that generalist wetland or open ground species, for example, occur together with more fastidious riverine specialists. In Britain this latter group consists of just sixty-one species (depending on the definitions used to classify ERS and our current state of knowledge on habitat associations) whereas the total beetle fauna regularly occurring in such habitats is more likely to be in the region of a thousand species. For some of the latter ERS contribute a significant proportion of their known GB sites but they may also occur on sand dunes or coastal cliffs, for instance. Invariably the important habitat elements are bare sediments in wet or dry conditions and for the species concerned it doesn’t matter if these are alongside a river or in a dune slack.

The stenotopic ERS specialists are the most important group of beetles occurring along our rivers but we also need to take account of the contribution exposed riverine sediments make to the conservation of other bare ground species in Britain. The list which follows recognises this and incorporates species that do occur on ERS but which are also characteristically found in other habitat types, such as sand dunes, soft rock cliffs, gravel pits, pond and lake margins, etc., where the presence of bare sediment is of fundamental importance for some stage of their life cycle. Of course, in many cases we do not have the ecological information to be certain about the life cycle of such species and an assessment has been made on the basis of recorded habitat associations. There are many grey areas but the following provisional list, produced in consultation with Jon Sadler and Peter Hammond, represents those 130 species whose occurrence on riverine sites is strongly influenced by the continued deposition of bare sediment along the river channel, either in the form of shoals or as eroding banks.

Once final agreement has been reached, this list will be used for the purpose of evaluating the relative value of different river systems in Britain for the conservation of their characteristic beetle faunas (see http://khepri.uk/main/ for information on the Saproxylic Quality Index as background to the general approach). At that stage scores will be assigned to each species in line with improved knowledge of their distribution and status in GB (for proposed changes to status see: http://yrefail.net/Coleoptera/ersqi_status_changes.htm . Comments are welcomed (e-mail: [email protected]) on any aspect of this attempt to define the ERS beetle assemblage.

Species dependent for at least some stage in their life cycle on bare or sparsely vegetated sediments on the banks of rivers. Some of these species may also inhabit exposed lacustrine sediments, particularly where wave action forms banks of sediment on lake shores, as these features are in many ways ecologically similar to riverine shoals.

Species strongly associated with exposed riverine sediments for at least some stage of their life cycle, but also occurring in a wider range of habitat types, such as flushes, seepages, pond margins, etc., where the presence of bare sediment is of fundamental importance for some stage of their life cycle.

In each case, there may be rare instances where the listed species have been recorded in atypical habitats, but the over-riding perception of their ecological requirements is such that the species in general is considered to exhibit the fidelity indicated.