e-Digest Statistics about: Wildlife
Butterflies, dragonflies and grasshoppers
The Biological Records Centre (BRC), set up in 1964 and now part of the Centre for Ecology and Hydrology (CEH), has computerised data sets that include about 6 million individual records of some 10,000 taxa [16]. Table 14 presents data for changes in geographical distribution of GB butterflies, dragonflies and grasshoppers. For each species in turn, 10km squares have been compared between two periods (i.e. before 1982 and 1995-99 for butterflies, before 1980 and 1980-92 for dragonflies and, before 1980 and 1980-99 for grasshoppers), and the presence or absence of the species noted for each square. The number of squares for each species where presence or absence was noted have been adjusted further to take account of recorder effort so as to make the results between different periods more comparable. The table shows the number of species found in each landscape type which increased or decreased by ten per cent or more, taking into account recorder effort.
The result of the above is a measure of the balance between those species increasing and those decreasing. This does not necessarily mean that populations are being affected in the same way. It may be that although a species is found to be present in relatively fewer squares from one survey period to the next, its actual population has increased and it is just inhabiting a smaller area. Caution must be exercised in the interpretation of these data because estimates are derived from sample-based surveys (and so are subject to sampling errors) and there may be some differences in the way these data have been recorded by different observers in the field.
In Detail:
Wildlife monitoring (Environmental Change Network)Further Information:
- Source:
- Biological Records Centre
- Key Facts:
- Butterfly populations
- Moth populations
Data Tables:
- References, further reading and links to other resources:
- [16] Parr, T.W., Bunce, R.G.H., Hallam, C., Scott, A., Eversham, B.C., Harding, P., Roy, D., Henderson, I.G., Baillie, S.R., Crick, H.P., Furse, M.T., Harris, S. and Woiwood, I.P., (1996). Information and indicators to give an overview of UK wildlife. Institute of Terrestrial Ecology: Final Report to DoE, 1996.
- Internet Links:
- Biological Records Centre
- Defra: Wildlife & Countryside, The UK Biodiversity Action Plan (UKBAP)
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Page last modified: 16 September 2003
Page published: 10 September 2003