South East England Biodiversity Forum

Lowland acid grassland

What is it?

Lowland dry acid grassland typically occurs on nutrient-poor, generally free-draining soils. The Habitat Action Plan (HAP) includes both enclosed and unenclosed acid grassland throughout the UK lowlands (normally below c. 300m). It covers all acid grassland managed in functional enclosures. Swards in old and non-functional enclosures in the upland fringes, which are managed as free-range rough grazing in association with unenclosed tracts of upland, are excluded. It often occurs as an integral part of lowland heath landscapes, in parklands and locally on coastal cliffs and shingle. It is normally managed as pasture.

Often forming a mosaic with dwarf shrub heath (the latter being covered in the separate lowland heathland action plan) acid grasslands can have a high cover of bryophytes and parched acid grassland can be rich in lichens. It is very variable in terms of species richness and stands can range from relatively species-poor (less than 5 species per 4m²) to species-rich (in excess of 25 species per 4m²).

Lowland Dry Acid Grassland can support a wide range of plant species and is an important habitat for invertebrates. There has been a substantial decline in the resource over the last century, mainly due to agricultural intensification.

While historically there has clearly been both large-scale direct loss and reduction in quality of lowland acid grassland, it is difficult to quantify these with precision because the habitat has frequently either been counted other grassland types (eg. unimproved neutral grassland) or included within lowland heathland. Estimated losses of unimproved lowland grassland in England and Wales between 1930 and 1984 were 97%.

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

The situation in the South East

Extent in England 20,000
Extent in the SE region  5,000
Percentage UK resource in the SE   25%
Extent covered by SSSI designation   data to be added

 

Lowland acid grassland is a priority habitat for nature conservation because it is a rare and threatened habitat. In the South East there is just 5,000 ha of this habitat, representing about 25% of the UK resource of 20,000 ha, and it is of national importance.

There are two major concentrations in the region that lie within European sites (SAC/SPA). These are in the New Forest (Hampshire) and at Dungeness (Kent).

Rate of change

 County 1998 extent (ha)  2008 extent (ha) 
 Berkshire  40  108
 Buckinghamshire  unknown  17
 Hampshire  unknown  4310
 Isle of Wight  90  122
 Kent  420  174
 Oxfordshire  unknown  47
 Surrey  unknown  225
 Sussex  unknown  150
 Total  unknown 5153
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. Please note that some of the changes listed here are due to improvements in mapping and habitat definition. 

 

 Current threats

The factors currently affecting acid grassland reduce the quality and quantity of the habitat. The fragmentation of the habitat brings increased risk of species extinctions in the small remnant areas. The factors include:

  • Agricultural intensification by use of fertilisers, herbicides and other pesticide, liming, re-seeding or ploughing for arable crops
  • Agricultural and other management neglect leading to rank overgrowth, and bracken Pteridium aquilinum and scrub encroachment
  • Over-grazing is a more localised problem, and is sometimes associated with supplementary feeding which can cause localised sward damage
  • Afforestation, particularly with softwoods on light sandy soils
  • Development activities such as mineral and rock extraction, road building, housing and landfill
  • Atmospheric pollution and climate change, the influence of which is not fully assessed

Vision for lowland acid 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, eg. inadequately managed public access
  • Re-creation of lowland acid grassland on appropriate sites to restore some past losses, including the linking up of fragmented sites
  • Greater public appreciation of lowland acid grassland and their 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 acid grassland areas under pressure for increasing new housing, such as the Thames Basin Heaths

How we can deliver this vision