Unimproved neutral grassland

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Abridged version taken from the Wiltshire Biodiversity Action Plan (BAP)

Introduction

Unimproved neutral grassland is usually present in the form of meadows and pastures that occur on soils that are neither markedly acid nor basic, and which have not been subject to any significant degree of agricultural intensification. Unimproved grassland is also frequently encountered in many transitional situations alongside wetland communities, within woodlands and on road verges, as well as in mosaics with chalk grassland (Salisbury Plain) or mosaics with limestone grassland (Wiltshire Cotswolds). The alternation in management between hay meadow and pasture is also not uncommon.

The two principal vegetation communities associated with unimproved neutral grassland is the National Vegetation Classification (NVC) category of MG4 (Mesotrophic Grassland 4): Meadow Foxtail – Greater Burnet community of unimproved wetter hay meadows, associated with slightly calcareous alluvial meadows that are seasonally flooded; and the MG5: Black knapweed crested dog’s-tail hay meadows and pasture community associated with more free-draining neutral clay-based soils.

Importance

Lowland unimproved neutral grassland is the single most threatened type of grassland habitat in the UK and has suffered the greatest loss in the last 70 years. Whilst both MG4 and MG5 grassland communities are nationally rare habitats, the MG4 community is particularly rare, both in the UK and in Europe as a whole, such that it is listed in Annex 1 of the EU Habitats Directive. Wiltshire is second only to Oxfordshire for the area of this rare grassland community that it possesses. North Meadow National Nature Reserve (managed by English Nature) and Clattinger Farm Nature Reserve (managed by Wiltshire Wildlife Trust) are both Sites of Special Scientific Interest (SSSI) under UK legislation and Special Areas of Conservation (SAC) under the European Habitats Directive.

Unimproved neutral grasslands are floristically rich, particularly when actively managed as hay meadows. Whilst the very rare MG4 community is not as floristically diverse as the drier MG5 community, it is characterised by the presence of a number of rare and uncommon species, such as snake’s-head fritillary, adders tongue fern and downy-fruited sedge, which have the major part of the their UK population in Wiltshire. The floristic richness of hay meadows is associated with a similarly rich invertebrate fauna. The unimproved neutral grasslands of the river valleys are important for wading birds such as the lapwing and snipe as well as golden plover in the winter. The brown hare can be found in the drier neutral meadows and pastures of Wiltshire, another UK BAP species which has suffered a significant national decline.

The wealth of colourful wild flowers and butterflies to be found in unimproved neutral hay meadows provides a particularly satisfying experience for visitors to nature reserves and other publicly accessible sites. As a consequence, the opportunity exists to interest many people to the cause of nature conservation who might otherwise not become involved. For many, the flowering of the snake’s-head fritillaries at North meadow has become an annual pilgrimage.

Extent and distribution

The UK Biodiversity Action Plan Statement 1995 indicates that there is now less than 15,000ha of species-rich neutral grassland remaining in England and Wales. Of this, less than 4,000ha of MG5 grassland survives and less than 1,500ha of MG4. A more up to date figure from DEFRA indicates that there are now 8,500ha of species-rich neutral grassland in England.

In Wiltshire, the lack of basic (Phase 1) habitat survey for the county makes estimates for overall cover of unimproved neutral grassland difficult. Known sites which have been found to meet the criteria for designation as SSSIs and/or recognition as County Wildlife Sites (CWS) amount to just over 500ha, of which around 150ha is MG4 grassland and around 350ha is MG5. This represents 10% and 8% respectively of the remaining UK resource of these two key neutral grassland communities. New sites continue to be discovered, particularly through the work of the Wiltshire Wildlife Sites Project (part funded by the Council) and as a consequence of surveys carried out in relation to development proposals.

Unimproved neutral grassland has a wide and scattered distribution throughout the county. This reflects the fragmented nature of much of the surviving resource. The exception to this general pattern is the concentration of unimproved MG4 wet hay meadow grassland in the Upper Thames Valley in North Wiltshire where two sites alone, North Meadow (40ha) and Clattinger Farm (60ha), account for two thirds of the known unimproved MG4 in the county. Unimproved neutral and slightly calcareous alluvium grasslands are the primary biodiversity interest of the Thames and Avon Vales Natural Area.

The drier MG5 neutral grassland has a much more fragmented distribution and frequently occurs in mosaics with limestone grassland communities (Cotswold Natural Area) or with chalk grassland communities (Marlborough Downs and South Wessex Downs Natural Areas). Unimproved neutral grassland also occurs in transitional situations throughout the county in proximity to wetland, woodland and semi-urban habitats. Some good, albeit small, areas of unimproved neutral grassland also occur on some road verges.

Trends

Nationally, unimproved neutral grasslands were found in 1984 to cover only 3% of the area of England and Wales they occupied in the 1930s. More recent estimates suggest that the cover may be down to only 2% of the 1930s figure. In some areas of the country, losses have continued through the 1980s and 1990s at rates ranging from 2% to 10% per annum.

In Wiltshire, 19 known sites of unimproved neutral grassland (MG4 and MG5) covering an area of 62.5ha have been destroyed since 1990 and a further 62 sites covering an area of 73.6ha have been degraded in the same period. Analysis of the causes of destruction indicated a variety of activities ranging from motorbike scrambling to by-pass construction but the overwhelming cause was agricultural improvement, particularly ploughing-up and the application of chemicals. Causes of degradation again included agricultural improvement as a significant cause but also featured both over- and under-grazing by stock and encroachment of scrub due to a lack of management as key factors.

The loss and degradation of habitat is reflected in the fate of associated species. Thus only 30 pairs of curlew tried to breed in the whole of Wiltshire in 1994, compared to 70 in 1969.

Key species

• Marsh fritillary
• Brown hare
• Skylark
• Waders: lapwing, curlew, snipe, golden plover
• Adder’s-tongue fern

MG4 grasslands in Wiltshire

• Snake’s-head fritillary
• Meadow foxtail
• Greater burnet
• Meadow rue
• Meadow brome
• Pepper saxifrage

MG5 grasslands in Wiltshire

• Downy-fruited sedge
• Green-winged orchid
• Dyer’s greenweed
• Meadow thistle
• Tawny sedge
• Black knapweed
• Crested dog’s-tail

Last updated: 23 June 2009