South East England Biodiversity Forum

Calcareous grassland

What is it?

Silver studded blue butterflyLowland calcareous grasslands are developed on shallow, lime-rich soils generally overlying limestone rocks, including chalk. The definition of calcareous grasslands covers a range of plant communities in which lime-loving plants are characteristic.

 

In the context of the Habitat Action Plan (HAP), lowland types are defined as the first nine calcareous grassland National Vegetation Classification communities, CG1 to CG9. With the exception of CG9, Sesleria albicans - Galium sterneri grassland, which straddles both lowlands and uplands, these communities are largely restricted to the warmer and drier climates of the southern and eastern areas of the United Kingdom.

A high proportion of the South East’s lowland acid grassland, or land that is suitable for the restoration or re-creation of lowland acid grassland, is owned or managed by conservation bodies, notably Natural England, the National Trust, the Wildlife Trusts and the RSPB.

Please see the UK BAP website or the BAP habitat definition or the UK BAP habitat definition for more information.

The situation in the South East

 

Extent in England  40,600 ha
Extent in the SE region  8,245 ha
Percentage UK resource in the SE  20%
Extent covered by SSSI designation  app. 63% of regional resource

 

Rate of change  

County
 1998 extent (ha)  2008 extent (ha) 
 Berkshire  180  209
 Buckinghamshire  350
 235
 Hampshire  2800  1991
 Isle of Wight  655   658
 Kent  1500  1500
 Oxfordshire  550  715
 Surrey  325

 307

 Sussex  2650  2630
 Total  9450  8245

1998 data taken from 'The Biodiversity of South East England - An Audit and Assessment' published by the Wildlife Trusts of South East England and the RSPB, South East and Central Regions  

2008 data taken from regional or national BAP habitat inventory. The majority of the change in extent identified in the table above is due to improvements in data rather than change in habitat area.

Current threats

Both the quality and quantity of calcareous grassland is under threat and it is becoming increasingly fragmented. For example, a survey of the Lincolnshire Wolds found that 66% of sites were less than 1ha in size and none was more than 10ha in size. As it becomes more fragmented there is a greater risk of species extinctions in the small areas that remain.

The factors that are causing this include:

  • Greater intensification of agricultural with the use of fertilisers, herbicides and other pesticides, and re-seeding or ploughing for arable crops.
  • More arable farming which has reduced the availability of livestock in many lowland areas. Without grazing there is an increasing dominance of coarse grasses such as tor grass Brachypodium pinnatum and false oat grass Arrhenatherum elatius, plus invasion by scrub and woodland, leading to losses of calcareous grassland flora and fauna.
  • Overgrazing, which is a less widespread problem and is sometimes associated with supplementary feeding, but which can cause localised sward damage due to trampling and long-term nutrient enrichment.
  • Development activities such as mineral and rock extraction, road building, housing and landfill.
  • Localised afforestation with hardwoods and softwoods.
  • Recreational pressure bringing about floristic changes associated with soil compaction at some key sites.
  • Invasion by non-native plants, including bird-sown Cotoneaster species, causes problems by smothering calcareous grassland communities at some sites.
  • Atmospheric pollution and climate change, the influence of which is not fully assessed.

Vision for lowland calcareous grassland

  • The South East Biodiversity Forum’s vision for this habitat is that there should be:
  • No further loss of existing habitat
  • Good management, including where appropriate scrub control, light grazing and visitor management, on all extant sites
  • No damage to site integrity from activities arising outside the sites, e.g. inadequately managed public access
  • Re-creation of lowland calcareous grassland on appropriate sites to restore some past losses, including the linking up of fragmented sites
  • Greater public appreciation of lowland calcareous grassland and the habitat’s specialist wildlife, including greater awareness of the impacts of human pressures, such as dog-walking, mountain-biking, dumping of waste
  • Creation of alternative green space around important lowland calcareous grassland areas under pressure for increasing new housing, such as the Thames Basin Heaths

How we can deliver this vision