Chalk grasslands develop on shallow lime-rich soils, which occur in London mainly on the parts of the North Downs in the south and Chilterns in the west. Nutrient-poor and free-draining, they support a wide array of wildflowers, butterflies, grasshoppers and other invertebrates, many of which are restricted to chalk soils. For the purposes of the plan, the habitat also includes young chalk scrub that has developed through a lack of management. Mature scrub and young chalk woodlands are not included.

Grass species like red fescue, sheep's fescue and quaking grass are common, along with plants such as wild thyme, marjoram and common bird's-foot trefoil. In addition, chalk grasslands support a range of orchids, many of which are nationally uncommon or scarce. The habitat is crucially important for butterflies, including those that are nationally or regionally scarce, such as grizzled skipper, dingy skipper, chalkhill blue, dark green fritillary and marbled white. Of particular note is the small blue.

Traditionally chalk grasslands were kept open largely by grazing, primarily by sheep, although rabbits were also responsible for maintaining a short sward. Grazing declined after the 19^th century and by 1945 few areas in London were grazed. In the 1950s myxomatosis devastated the rabbit population, which further reduced grazing pressure and led to the spread of scrub and eventually woodland.

London's suburban development during the inter-war period led to expansion of residential areas onto the chalk. The establishment of the Metropolitan Green Belt in 1949 was instrumental in preventing further significant loss through development, and many tracts became secured by public authorities and retained as public open spaces. However, much of the rest was of declining value as pasture and has since been converted to arable land or is grazed intensively by horses. In recent years, the identification of chalk grasslands as important resources for biodiversity has led to establishment of chalk grassland nature reserves in an effort to restore and conserve them. Scrub-clearance remains a key issue for managers.

There are about 320 hectares of chalk grassland in London, just over 3% of that of south-east England. This is distributed across a number of sites within five boroughs: Croydon (184 ha), Bromley (92 ha), Sutton (37 ha), Hillingdon (6 ha), and Lewisham (<1 ha). Most of these sites lie on the northern parts of the North Downs, especially along the slopes of a number of dry valleys in Bromley and Croydon.

The lack of livestock grazing on chalk grassland in London has been the principal factor leading to loss of grassland to scrub and woodland. Changes in market conditions have severely affected farming profits, leading to the continued decline in serious agricultural commitment in the relatively under-productive North Downs region.

The loss of chalk grassland through habitat fragmentation has resulted from arable conversion, agricultural improvement, scrub encroachment, development, quarrying and recreation. This results in isolation of small areas of chalk grassland within the outer suburban matrix of London, making populations of species less viable and positive management more difficult.

The growth of leisure activities on London's chalk grasslands has grown demonstrably since the start of the 20^th century and can have a detrimental effect. In recent years off-road motorcycling, scrambling and 4-wheel drive motoring have all become significant local problems, causing erosion, vegetation damage and disturbance to the tranquility of such sites.

Hawthorn, blackthorn, dogwood, bramble, ash and some exotic species may colonise chalk grassland to the detriment of other species that depend on the open nature of the habitat.

There may be local impacts caused by surface run-off from adjacent roads (including salt), nutrient enrichment from vehicle emissions and even air, noise and light pollution. Street lighting adjacent to chalk grasslands will interfere with the behaviour of glow-worms and can hence have an impact on local population sizes. Occupation of sites by travellers, fly-tipping and illegal grazing can also have detrimental effects. Removal of chalk grassland species (including butterflies, reptiles and orchids) by collectors has been a problem in the past, and probably still continues at a very low level, as does the deliberate introduction of such species onto sites. These issues have not been sufficiently researched.

There are four Sites of Special Scientific Interest (SSSI) within London that consist primarily of chalk grassland. A fifth site, Croham Hurst (Croydon), includes an area of chalk grassland scrub which was recommended for denotification in 1996. Only one site, Roundshaw Downs in Sutton, has been declared a Local Nature Reserve (LNR).

Of the total resource in London, some 20 sites containing chalk grassland have been designated as Sites of Metropolitan Importance for nature conservation and a further 30 sites are of Borough Importance.

London's chalk grasslands support a range of protected species. Of particular importance are early gentian (1 site), greater yellow-rattle and small blue butterfly. Greater yellow-rattle is a nationally rare endemic plant, which has the bulk of its UK population on London chalk grasslands. The small blue butterfly is found on a number of London sites, including three in Sutton, two in Croydon and two in Bromley. Both this species and its larger relative the chalkhill blue are protected only from trade, however. Other protected species associated with London's chalk grasslands include common lizard, slow-worm, adder and badger.

In the past, species-rich chalk grassland was maintained as an incidental result of traditional agricultural practices. In recent decades, these practices have either disappeared completely in London, or been significantly altered through the impact of modern technology. The management mechanisms that are currently in place are either modifications of standard agricultural practices, or are replications of traditional practices such as hay cutting, often led by local authorities.

The Downlands Countryside Management Project (DCMP) has been active on a number of London chalk grasslands, providing volunteer labour, expert advice and importantly, livestock for grazing. They assist in the management of a number of chalk grassland sites in London and hold a roving flock of 40 sheep that can be moved around different sites.

The Countryside Stewardship Scheme, administered by the Farming and Rural Conservation Agency, currently targets chalk grassland. A number of sites have been entered into the scheme. Individual agreements are for 10 years and provide both capital and revenue costs to benefit biodiversity, as well as access and general environmental improvement. Scrub clearance, stock fencing, grazing and reversion of arable land to grassland can be funded.

7. Objectives, Actions and Targets

Most of these actions are specific to this habitat. However, there are other, broader actions that apply generically to a number of habitats and species. These are located in a separate 'Generic Action' section which should be read in conjunction with this document. There are generic actions for Site Management, Habitat Protection, Species Protection, Ecological Monitoring, Biological Records, Communications and Funding.

Relevant Action Plans

London Plans

Woodland; Private Gardens; Churchyards and Cemeteries; Railway Linesides; Farmland; Parks, Amenity Grasslands and City Squares; Wasteland Land.

National Plans

Lowland Calcareous Grassland; Calcareous Grassland Habitat Statement.

Key References

Nature Conservancy Council (1986). The management of chalk grassland for butterflies Focus on nature conservation no.17.

Abbreviations

Contact

The Lead for this habitat is London Wildlife Trust.

marbled white © mike waite