§ Norman BakerTo ask the Secretary of State for Environment, Food and Rural Affairs what the average number of species in(a) grassland and (b) woodland was (i) on the latest date for which figures are available and (ii) 10 years ago, broken down by region. [165739]
§ Mr. BradshawThe information is as follows:
(a) Grassland:
Semi-natural grasslands are divided into six main Biodiversity Action Plan priority types. The figures in the table give an indication of the average number of plant species expected in a 4m2 quadrat, assuming ideal management. But large variation in species number can occur depending on the different sub-types of grassland within the broad categories.
BAP priority grassland type Average number species per 4m2 quadrat
Lowland calcareous grassland 23 Upland calcareous grassland 29 Lowland meadows 26 Upland meadows 26 Purple moor grass and rush pastures 25 Lowland acid grassland 18 The Countryside Surveys were established to monitor changes in land cover, landscape and biodiversity in Great Britain. Data has to date been collected for 1984, 1990 and 1998. This shows a change in mean number of species between 1990 and 1998. In the case of neutral grassland; calcareous and acid grassland in the west lowlands, a small decline in mean number of plant species/plot was recorded. But these changes were not statistically significant. A statistically significant increase in mean number species/plot was recorded for acid grassland in the uplands.
The random sampling approach means that for some rarer habitats, such as calcareous grasslands, the sample sizes were small decreasing the precision of the results.
(b) Woodland:
Woodlands are structurally diverse, and habitat for a vast number of species, including vascular plants, birds, mammals, invertebrates, lichens, fungi and soil microbes. No comprehensive study has been undertaken.
Woodlands can be categorised by broad Biodiversity Action Plan type; whether they are recognised as ancient or recent; semi-natural or plantation. Generally there is higher vascular plant species on ancient, semi-natural woodland. The survey data available over this time span includes all broadleaved woodland.
Average species richness for different woodland types, using 4x4m or 10x10m quadrants. Adapted from Rodwell 1991
Priority BAP Habitat type Average number of species per plot
Wet woodland 25 Upland ash 36 Upland oak 29 Beech 15 Yew 5 The Countryside Survey also covers woodland habitat, and can be used to show relative change over 1197W the same time period. The methodology used did not distinguish between different woodland types shown above, nor did it specify ancient woodland, so figures may be lower than expected.
The following table below shows the mean species richness for a random sample of woods in England and Wales, between 1990 and 1998, using 200m2 quadrants. From Haines-Young et al (2003).
Zone Number of samples
Mean species richness 1990
Mean species richness 1998
1 57 13.79 11.26 2 43 16.93 15.93 3 18 18.89 16.89 Zones: 1= Easterly and southerly lowlands 2= West lowlands 3= Uplands