Acid grasslands - lowland

Context

Lowland acid grassland is characterised by vegetation dominated by grasses and herbs on a range of lime-deficient soils which have been derived from acid rocks such as sandstones, acid igneous rocks and on superficial deposits such as sands and gravels. Although the habitat is typically species-poor, a wide range of communities occur in the UK. In the lowlands, acid grasslands are now rare and, particularly in areas such as East Anglia, they provide an important reservoir of rare species. This habitat type includes a range of types from open communities of very dry sandy soils, which may contain many annual species, through closed pastures on red brown earths, to damp acidic grasslands typically found on gleys and shallow peats. Lowland is defined as below the level of agricultural enclosure. The altitude at which this occurs varies across the UK, typically becoming higher as one travels South.

Acid grassland is characterised by a range of plant species such as heath bedstraw Galium saxatile, sheep`s-fescue Festuca ovina, common bent Agrostis capillaris, sheep`s sorrel Rumex acetosella, sand sedge Carex arenaria, wavy hair-grass Deschampsia flexuosa, bristle bent Agrostis curtisii and tormentil Potentilla erecta, with presence and abundance depending on community type and locality. Acid grassland types found on coastal dune and shingle habitats are included in the Dunes, shingle and machair reporting category.

SSSIs can be notified if they qualify under criteria outlined in Chapter 3 Lowland grasslands of the Guidelines for Selection of Biological SSSIs. In Northern Ireland, ASSIs are selected on a very similar basis – the Guidelines for the Selection of Biological ASSIs in Northern Ireland is an addendum to the SSSI guidelines rather than an alternative.

Summary statistics

	SAC	A/SSSI	Total
Favourable condition	0%	38%	38%
Main monitoring coverage	N/A	E, S
Reported assessments	N/A	173	174
Completeness of assessments	100%	unknown
Distribution of features			GB

Number of assessments reported by country and site type

Country	SAC	SSSI/ASSI
England	1	161
Scotland	0	12
Wales	0	0
Northern Ireland	0	0
United Kingdom	1	173

SSSI features

List of SSSI and ASSI interest features in this reporting category

Interest feature name
Formal name	Informal name	No. of assessments reported
Acid grassland - lowland	Acid grassland - lowland	173

This list has not been fully standardised at a UK level yet. It is intended to show the principal constituent "feature types" for this reporting category.

Maps - distribution

UK distibution of reported interest features

Distribution of reported interest features.

Map showing the locations of the 10km squares in which at least one condition assessment has been reported. It does not show features that have not yet been assessed.

Maps - SSSI

Current condition of SSSI/ASSI features
Distribution of SSSI/ASSI features showing assessments of favourability (where unfavourable-recovering is counted as unfavourable).

Condition of SSSI/ASSI features, with those currently reported as unfavourable-recovering shown as favourable
The implication of the unfavourable-recovering condition assessments is that at some point in the future these features should become favourable. This map shows the effect of that recovery by counting the favourable and unfavourable-recovering assessments together.

IMPORTANT NOTE: we do not have information on the timescale of the predicted recovery, which may be influenced by many past, natural and human related factors. A sustained sympathetic management regime is more likely to result in favourable condition being attained.

Key: Proportion of assessed features on 10km squares that are favourable:

SSSI map legend - Proportion of assessed features on 10km squares that are favourable

Details of how these maps were produced

Condition summary

This lists the 10 different condition assessments and presents a bar chart showing the number of features within the SSSI series and the Natura 2000 series (either SPA for bird features or SAC for features other than birds). Note that for Natura 2000 we are able to estimate the number of features that have not been assessed during the 6 year reporting period - we are unable to do this for SSSI/ASSI because we do not have an overall list of notified interest features for these designations.

NB favourable unclassified and unfavourable unclassified have been used in this first six year cycle to get around difficulties in identifying trends in condition as common standards monitoring is implemented. It is expected that these categories will not be used for subsequent assessments of a feature.

Condition assessment - SSSI features

The number and proportion of assessments for SSSI/ASSI interest features falling into each of the condition categories. Note that the �unfavourable� category includes all reports of unfavourable condition except �unfavourable recovering� which is shown as a separate segment.

Adverse activities

The number of interest features where an activity has been reported as being implicated in the "unfavourable" condition of a feature. More than one adverse activity may be reported for each feature.

Management measures

For each "measure" the chart shows the number of interest features where that measure has been taken on a site to improve or maintain the condition of an interest feature. More than one measure may be reported for each feature assessed.

Interpretation

38% of lowland acidic grassland SSSI features reported are in favourable condition. Figures varied somewhat between England and Scotland, but in both countries less than half the total number of sites are considered to be in favourable condition. There is no reason to believe that the situation is different in Wales. The lowland acid grassland interest in the Habitats Directive is limited to inland dunes with open Corynephorus and Agrostis grasslands, for which there is only one SAC in England; this is reported to be in unfavourable-recovering condition. The unfavourable-recovering category accounts for a significant proportion of the assessments reported (31% of SSSI features). Thus many sites, although currently unfavourable, have management in place to promote a return to favourable condition.

Under-management is the main cause of unfavourable condition, specifically under-grazing and abandonment. Scrub and bracken encroachment are the common results, sometimes together with invasive species problems. Some sites are affected by over-grazing and nutrient enrichment. Underlying causes of under-management are still thought to be largely due to current agricultural economics and policies, exacerbated by for example, BSE and Foot & Mouth disease, leading to a reluctance to keep stock (large stock in particular) on pasture perceived to have little nutritional value. Nutrient-enrichment through fertilizer application is still a concern, but is very difficult to monitor. In addition, the extent to which atmospheric nitrogen deposition is affecting the composition of grassland sites is a largely unknown quantity.