e-Digest Statistics about: Wildlife
Plants
Table 15 presents BRC data for changes in geographical distribution in GB of vascular plants [16]. The information is broken down not only by landscape type but also by habitat groups within each landscape. The period of comparison is between the two Botanical Society surveys of 1952-60 and 1987-88. Again caution must be exercised in the interpretation of these data because estimates are derived from sample-based surveys and there may be some differences in the way these data have been recorded by different observers in the field.
The BRC change data tend to reflect changes in rarer and more specialised plant species, which are usually restricted to comparatively small areas of semi-natural habitat and many of which may be absent from the vast majority of 1km squares in Britain. In contrast the 1990 Countryside Survey (CS1990) data (presented later in the topic in Tables 17 and Table 18) tend to reflect changes in more common plant species. The results for the BRC and CS1990 change statistics also cover different timescales. Thus while the two approaches are complementary, it is not surprising if some of the changes they reveal are apparently contradictory.
Nationally Rare and Threatened plants are given in the Red Data List and have been defined in the past as those present in 15 or fewer 10km squares in GB. During 1999 the third edition of the British Red Data Book was published (this included the vascular plants Red Data List) [17]. The lists were drawn up using newly agreed revised IUCN threat categories and do not adhere rigidly to the criterion of 15 or fewer 10km squares. The next tier of rarity recognised in Britain comprises of Nationally Scarce species which are defined as those species which are recorded as present in 16-100 10km squares in GB.
'The New Atlas of British and Irish Flora', which charts the distribution of every flowering plant and fern species across Britain and Ireland, was launched in September 2002. The 910-page volume, produced from nine million records, features 2,412 maps to illustrate the distribution of flowering plants and ferns. A summary of the results can be found in The Changing Flora of the UK. Summary data are available in Tables 28, 29 and 30.
Table 16 shows the numbers of Nationally Rare or Threatened and Scarce species in 10 major habitat types based on data from the 1994 publication Scarce Plants in Britain [18]. The allocation of some species to a single broad habitat type is a little artificial as some species could be placed in more than one category. Estimates have been made of the numbers of 10km squares in which the Rare, Threatened and Scarce species were recorded between 1970-1992. The table summarises these estimates and also shows the numbers of species whose presence was recorded in fewer squares for 1970-1992 than for 1930-1960 (as recorded in the 1962 Atlas of the British Flora) [19].
Care should be taken when comparing records of species presence from the 1962 Atlas with species presence recorded between 1970-1992, because the recent records for most species are more comprehensive than the earlier records collected for the Atlas. Thus while many species apparently show an increase in range since 1970, in many cases this is likely to have resulted from earlier under-recording of the pre-1960 records rather than genuine increases in ranges.
Twenty seven Nationally Scarce species (given in the table) showed a decrease for recent records, but because of the earlier under-recording the extent of the real decrease is believed to be underestimated. The true number of the 261 Scarce species which have declined in distribution will be larger than 27. However, these 27 species are likely to be among the species with greatest decreases, and hence they provide some indication of the habitats with species in greatest decline. 15 other Nationally Scarce species also showed a recorded decrease but they are not believed to be in genuine decline (and have thus been excluded from the last two columns of the table). These recorded decreases are believed to be attributable to under-recording in 1970-92 because of various recording difficulties (for example problems of access and identification, taxonomic uncertainty, etc). Eight of these 15 species come from montane habitats (e.g. parts of the Scottish highlands).
Plant Diversity
In 1998, 569 sample squares, each measuring 1km x 1km were visited, 61 more than in the previous survey in 1990. These sample squares were chosen as being representative of the range of environmental conditions in Great Britain. Vegetation data were collected from a sample of fields, woods and open moorland (Main plots) and also from linear features such as hedges, roadside verges and stream banks (Linear plots) each 1km square. Most of these plots had been surveyed in 1990, and some in 1978, enabling analysis of changes in plant diversity over time. Each plot surveyed was classified into distinct vegetation types characteristic of the wider countryside using the Countryside Vegetation System (CVS), developed within the ECOFACT research project [21]. For the purpose of statistical analysis of change, the 100 vegetation classes of the CVS are aggregated into eight major vegetation groups (see Box 2) which are used to report change in table 17 and table 18.
| Box 2 The eight major vegetation groups of the Countryside Vegetation System | ||
|
Major vegetation group (Aggregate Class) |
Description |
|
| I | Crops/weeds | Weedy communities of cultivated and disturbed ground, including species poor arable and horticultural crops. |
| II | Tall grassland/herb | Less intensively managed tall herbaceous vegetation typical of field edges, roadside verges, stream sides and hedge bottoms. |
| III | Fertile grass | Improved or semi improved grasslands. Often intensively managed agricultural swards with moderate to high abundance of perennial rye grass. |
| IV | Infertile grass | Less productive unimproved and often species rich grasslands in a wide range of wet to dry and acidic to basic situations. |
| V | Lowland wooded | Vegetation dominated by shrubs and trees in neutral or basic situations, generally in lowland Britain. Includes many hedgerows. |
| VI | Upland wooded | Vegetation of broad leafed and conifer woodland often in more acidic situations, generally in upland Britain. |
| VII | Moorland grass/mosaic | Extensive, often unenclosed and sheep grazed hill pastures throughout Britain. |
| VIII | Heath/bog | Vegetation dominated by heathers. Included drier heaths as well as bog. Mostly in the uplands. |
Table 17a and Table 17b compare the mean number of species in each plot between the 1978, 1990 and 1998 surveys- regardless of whether the major vegetation group of the plot changed between 1978 and 1990 or whether the plot was a main or linear plot. Hence, these figures reflect gross changes and include changes both within and between different vegetation groups. The plots have been allocated to the vegetation groups recorded in 1978. Table 17a shows changes in plots in 256 squares surveyed in both 1978 and 1990 whereas table 17b shows changes in plots in 501 squares surveyed in both 1990 and 1998. The data presented for 1978-90 and 1990 -98 are not directly comparable due to the change in number of survey squares. The results are further broken down by Environmental Zone (EZ), details of which are shown in Box 9.2. These cover the range of environmental conditions found in the UK, ranging from the lowlands of the south and east, through to the uplands and mountains of the north and west. As might be expected, the vegetation groups are not equally distributed in all Environmental Zones, for example the 'crops and weeds' vegetation group is not found in the true uplands (EZ6).
| Box 9.2 Description of Environmental Zones | |
|
Zone |
Description |
|
1 |
Easterly lowlands (England/Wales) |
|
2 |
Westerly lowlands (England/Wales) |
|
3 |
Uplands (England/Wales) |
|
4 |
Lowlands (Scotland) |
|
5 |
Intermediate uplands and islands (Scotland) |
|
6 |
True uplands (Scotland) |
Table 17c and Table 17d shows the percentage changes in species numbers between 1978 -90 and 1990-98. For Great Britain as a whole, between 1990 and 1998 there were significant declines in species recorded in tall grass/herb, fertile grassland and infertile grassland. However the rate of decrease in species in infertile grassland has reduced since 1978. The majority of change between 1990 and 1998 occurred within the Westerly lowlands (EZ2) including a significant increase in diversity in 'crops and weeds'.
Table 18a and Table 18b shows changes in plant diversity, between 1990 and 1998, according to the different plot types, namely the Main plots and the three types of Linear plots - roadside verges, hedges and stream-sides. Despite their much smaller area (Table 18a), Linear plots had similar numbers of species per plot to the Main plots. The results show (Table 18b) significant loss in infertile grassland in both the Main plots and the stream side Linear plots. The only significant increases in diversity occur in crops and weeds on roadside verges and lowland wooded in hedge plots.
In Detail:
- UK Biodiversity Action Plan
- Wildlife monitoring (Environmental Change Network)
Further Information:
- Source:
- Botanical Society, New Atlas of British & Irish Flora, JNCC, Countryside Survey
- Key Facts:
- Scarce and threatened native species
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.
- [17] Perring, F.H. and Farrell, L., (1983). British Red Data Books: 1. Vascular plants. 2nd edition. Royal Society for Nature Conservation, Nettleham.
- [18] Stewart, A., Pearman, D.A. and Preston, C.D., (1994). Scarce Plants in Britain. JNCC, Peterborough.
- [19] Perring, F.H. and Walters, S.M., (1962). Atlas of the British Flora. Thomas Nelson and Sons, London.
- [20] R Haines-Young (2000). Accounting for Nature: assessing habitats in the UK countryside, Defra London
http://www.cs2000.org.uk/Report_HTML/index.htm - [21] ECOFACT Module 1 Contract Report to Defra
http://www.ceh.ac.uk/products_services/publications/online/ECOFACT/volume1.htm
- Internet Links:
- Botanical Society of the British Isles
- Joint Nature Conservation Committee (JNCC)
- Countryside Survey 2000
- Defra: Wildlife & Countryside New Atlas of British & Irish Flora
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Page last modified: 16 September 2003
Page published: 10 September 2003