Habitat Action Plan
Acid Grassland

“By the middle of spring there may be on the [Clapham] Common little heaps of sandy material surrounding a miniature crater which leads to a deep hole, like the pipe of a toy volcano…shortly a red-tailed bee approaches, goes down the shaft, performs its business, and departs."
(Walter Johnson, 1930)

1.	Aims
•	To ensure the protection and optimal management of acid grassland in Greater London.
•	To improve on existing knowledge of its ecological value in the regional context.
•	To develop a more universal appreciation of the habitat and its wildlife, and secure the involvement of Londoners in its conservation. 

2.	Introduction
As its name suggests, acid grassland develops over acidic soils. These soils are usually derived from free-draining sands and gravels that are low in nutrients. The habitat generally consists of various fine-leaved grasses and associated wildflowers, such as common bent, red and sheep’s fescues, wavy hair-grass, sheep’s sorrel, tormentil, cat's-ear and heath bedstraw. This plan also addresses a less widespread type of acid grassland that consists mainly of purple moor-grass and is found where drainage is more impeded.
The soil conditions described above also support dwarf-shrub heathland. Much of today's acid grassland represents a degraded habitat which has lost its characteristic low-growing shrubs, such as heather, to various erosive forces. However acid grassland is an essential part of the habitat mosaic found on heathlands, and it is important to note that the present lack of heather is symptomatic of an imbalance caused by particular circumstances, rather than the undesirable replacement of one habitat by another.
Although acid grassland is a fairly meaningless concept for most people, there is no reason why the finer qualities of the habitat should not gain wider appreciation. Unlike chalk grassland, acid grasslands are not generally celebrated for their wealth of colourful wildflowers, although some of the characteristic species that do occur here are no less charismatic. These include harebell, common stork’s-bill, buck’s-horn plantain, heath milkwort and the diminutive bird’s-foot. Nationally scarce plants found in London’s acid grassland include clustered clover, upright chickweed and autumn squill. 
The acid grasslands of Greater London, south Essex and north-west Kent appear to be the natural home of a distinctive group of insects and spiders. A combination of factors appears to be responsible for this, including the loose and often bare soil, availability of nectar-rich wildflowers, plus the region's geographic location in the driest corner of the British Isles yet still close to the sea. Prominent within the group are many hole-nesting bees, wasps and ants, such as the rare mining bee Andrena florea. The UK distribution of many species is apparently very restricted and this unique assemblage has been collectively termed the ‘Thames Terrace invertebrate fauna'. 
More familiar insects frequenting acid swards are the small heath and small copper butterflies, while the hummocks of meadow ants are another common feature. The fungi found here may also be interesting. Associated birdlife includes the meadow pipit, skylark and, attracted by the rich insect pickings, the green woodpecker.

3.	Current Status
Acidic soils are fairly common in the Thames basin, particularly over the widespread Terrace Gravels laid down by the historic shifting course of the great river. Although there is plenty of potential for acid grassland to develop in Greater London, it is an uncommon habitat. This is a result of extensive development, conversion into farmland or amenity grassland, and quarrying for aggregates with later restoration to something quite different, such as open water.
Lowland dry acid grassland is listed as a priority habitat for conservation in the UK Biodiversity Action Plan. London’s estimated 1300 hectares contribute about 4% to the national resource. Because of the widespread distribution of acidic soils only six boroughs are without any acid grassland. Although there are several extensive areas, for example in Richmond Park, on Wimbledon Common and Putney Heath in Merton and Wandsworth, and at Wanstead Flats in Redbridge, a significant proportion occurs as widely scattered, overlooked fragments on the margins of more ubiquitous habitats such as amenity grassland, scrub, road and rail verges and on some longer-established wasteland sites. Thames Terrace invertebrates are often discovered on the latter, indicating the similarity between soil conditions of former industrial sites and the region's original grasslands.
Much of London’s remaining acid grassland has suffered in quality, due to a variety of factors. Ideally, it would be maintained by grazing animals and occur alongside stands of heather and gorse, small areas of bare ground and lichen cover, patches of scrub and peat-filled bogs. There would also be variation in structure within the grassland community reflecting its stage of succession. However, over-intensity of use or management neglect and consequent invasion by coarse grasses, bracken and developing woodland, are all too commonly associated with the habitat in London.

4.	Specific Factors Affecting the Habitat
4.1	Lack of a clear identity
Because of acid grassland’s somewhat lowly image and confusing identity as a habitat type, it is often undervalued, even by ecologists. This makes it particularly vulnerable to mismanagement, and beyond protected sites, frequently seen as expendable by developers and their advisers. Its status as a once widespread habitat comprising much of London’s rough grazing land, of particular importance to a suite of specialised invertebrates of national significance, is only beginning to be appreciated.
4.2	Amenity use
As the majority of London’s remaining acid grassland is found in public open spaces and in golf courses, there are often heavy pressures on site managers to accommodate conflicting recreational demands. Acid grassland therefore continues to be lost through inappropriate management (such as irrigation, reseeding and tree planting) to provide more formal recreation areas, and the reconfiguration of greens, fairways and so on. A lack of resources leads directly to passive neglect of the habitat, allowing bracken to take hold, and scrub and woodland to develop.
The acute level of recreational use in urban areas is itself a problem and commonly causes localised erosion and eutrophication by dog excreta. Fires are another hazard in public sites, which can provoke managers into keeping their grasslands mown too short to benefit wildlife.
4.3	Management constraints
The optimal management of acid grassland in London is constrained by several factors. Low-intensity grazing is currently considered to be the best method of achieving a varied range of conditions. Although deer herds have long been crucial to the maintenance of Richmond and Bushy Parks’ grasslands, and rabbit grazing is also locally important, the fragmented nature of the habitat often prevents grazing by stock. The average site is simply not large enough to support viable flock or herd sizes. Stock availability and disturbance by the public and their dogs are also prohibitive.
Mowing therefore tends to be the most widely applied method of maintaining the open nature of the habitat, although this is far from ideal as it can destroy the features important for supporting diverse invertebrate communities.
The more general effects of atmospheric pollution on this habitat are causing increasing concern. Vehicle and air traffic emissions contribute to changes within the plant communities, but are beyond the control of most site managers.

5.	Current Action
5.1	Legal status
Much of the acid grassland identified in the London Biodiversity Audit occurs within Sites of Importance for Nature Conservation (SINC), although there will undoubtedly remain important areas which have yet to be discovered.
Some sites containing acid grassland receive statutory protection as Sites of Special Scientific Interest (SSSI) or Local Nature Reserves (LNR). SSSI with acid grassland include Wimbledon Common (Merton and Wandsworth), Keston and Hayes Commons (Bromley) and Epping Forest (Waltham Forest and Redbridge). Richmond Park is both an SSSI and a National Nature Reserve. LNR include Stanmore Common (Harrow), Barnes Common (Richmond) and Hounslow Heath (Hounslow). Richmond Park, Wimbledon Common and Epping Forest are all candidate Special Areas of Conservation (SAC), to be designated under European legislation for their invertebrate and habitat interest.
Specially protected species associated with the habitat in London include adder, common lizard and possibly slow-worm. The protected Deptford pink is a nationally rare plant which may still occur in acid grassland sites such as Richmond Park and Blackheath (Greenwich). Many of the associated rare invertebrates are listed in the British Red Data Book (RDB), for example the mining bee Andrena florea, the bee wolf Philanthus triangulum and the digger wasps Diodontus insidiosus and Cerceris quinquefasciata.
5.2	Mechanisms targeting the habitat
These current actions are ongoing. They need to be supported and continued in addition to the new action listed under Section 7.
5.2.1	Management and restoration
Most protected sites have management plans and some have benefited from grant aid schemes, which offer finance towards fencing and scrub clearance projects. Mowing or, ideally, selective strimming, is the most convenient method for maintaining scrub-free grassland, although it is crucial for cutting regimes to be carefully worked out otherwise much damage can be done, especially to a site’s invertebrate interest. The regular creation of areas of bare ground is an ideal extra. Minor controlled fires have also been effective in halting succession on many sites.
Where appropriate, heathland creation within an acid grassland site can increase species and structural diversity. This has been attempted on Hounslow Heath and Hampstead Heath (Camden).

6.	Flagship Species
These special plants and animals are characteristic of acid grassland in London.

Harebell	Campanula rotundifolia	This, the “bluebell” of Scotland is a welcome addition to dry grassland swards late into the summer.	
Sheep's sorrel	Rumex acetosella	A humble member of the dock family, its blood-red leaves particularly characterise acid grassland and have been eaten as a wild salad plant in the past.	
Heath bedstraw	Galium saxatile	A sprawling plant, often found on the tops of anthills. In flower it has a foam-like appearance, and along with other bedstraw species was traditionally used to stuff pillows and mattresses. A chemical property may have repelled bed bugs and other parasites.	
Small copper butterfly	Lycaena phleas	The metallic orange of this tiny butterfly's forewing provides its common name. A common larval foodplant is sheep’s sorrel.	
Red-banded sand wasp	Ammophila sabulosa	This striking insect has a narrow, elongated waist and frequents sandy grassland sites, mainly in eastern boroughs. Wasps require warm, loose soil in order to breed but adults also need to forage on nearby nectar-rich wildflowers. Having dug her nest, the female wasp hunts caterpillars which can often much larger than herself. These are dragged back to the nest paralysed but still alive, and left for her larva to feed on when they hatch out a few days later.	
Green woodpecker	Picus viridis	Or “yaffle”, is frequently seen on the ground in acid grassland. A favoured food of this striking bird is ants, and it is these that bring it out from its more usual haunts amongst parkland trees and woodland.	

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.
Please note that the partners identified in the tables are those that have been involved in the process of forming the plan. It is not an exclusive list and new partners are both welcomed and needed. The leads identified are responsible for co-ordinating the actions – but are not necessarily implementers.

Objective 1	To secure appropriate management for acid grassland
Target: Appropriate management in place on all major existing acid grassland sites by 2011

Action	Target Date	Lead	Other Partners	
Establish network of acid grassland site managers and conservation bodies as an ‘Acid Grassland Working Group’	2002	RPA	Site Managers, LA, LWT, LNHS, GLA, EN, EFC	
Produce best practice habitat management guidelines 	2003	Working Group	EN, EFC	
Distribute guidelines to all acid grassland site managers	2003	RPA	Working Group	
Integrate acid grassland within heathland training programme in management, monitoring and interpretation for site managers	2003	Working Group	RPA, EN	

Objective 2	Conserve important species, with an emphasis on invertebrates, through better understanding of their ecology and habitat management needs
Target: Initiate a strategic conservation programme for invertebrate fauna found on acid grassland in London by 2006

Action	Target Date	Lead	Other Partners	
Produce and distribute interim guidance for site managers on appropriate management for invertebrate interest	2003	EFC	EN, GLA	
Source funding for targeted invertebrate survey of Greater London acid grassland	2003	Working Group	EN	
Investigate status of Thames Terrace invertebrate fauna in Greater London and use data to inform on selection of wildlife sites for planning protection	2006	EFC	LNHS, ICT, BC, EN, GLA, LWT	
Objective 3	Raise profile of acid grassland and develop appreciation of its ecological value
Target: Promote acid grassland using identified flagships and employing a strong invertebrate theme, through a series of public events by 2004

Action	Target Date	Lead	Other Partners	
Develop & distribute contacts for walk leaders and speakers to all site managers	2002	RPA	Working Group, EN	
Invite Ward Councillors to visit local sites, to appreciate site priorities & potential	2002	Working Group		
Produce a leaflet on London’s acid grassland resource, focussing on the national importance of conserving Thames Terrace invertebrate fauna	2007	GLA	LNHS, EN, BC, ICT 	

Relevant Action Plans
London Plans
Woodland; Heathland; Wasteland; Churchyard and Cemeteries; Parks, Amenity Grasslands & City Squares; Open Landscapes with Ancient/Old Trees; Railway Linesides.
Reptiles; Tower mustard; Humble bumble.
National Plans
Lowland Heathland; Lowland Dry Acid Grassland; Purple Moor-grass and Rush Pasture; Lowland Wood Pasture and Parkland; Built Environment and Gardens.
Skylark; Hornet robber-fly Asilus crabroniformis; A long-tongued bumble-bee Bombus humilis; Deptford pink.

Key References
Crofts, A & Jefferson R G, Eds. (1999). The Lowland Grassland Management Handbook (2nd Edition). English Nature/The Wildlife Trusts.
English Nature (1998). A review of the extent, conservation interest and management of lowland acid grassland in England (Vols. I & II). English Nature Research Report No. 259.
English Nature (2000). Lowland acid grassland, a rare and unique habitat.
English Nature (1998). Management of bare ground on dry grasslands and heathlands.
Harvey, P (2000). The East Thames corridor: a nationally important invertebrate fauna under threat. British Wildlife, 12 (2).
Johnson, W (1930). Animal Life in London. The Sheldon Press, London.
Kirby, P (1992). Habitat Management for Invertebrates: a practical handbook. JNCC.
Plant, C W & Harvey, P (1997). Biodiversity Action Plan. Invertebrates of the South Essex Thames Terrace Gravels - Phase 1: Characterisation of the existing resource.
Taylor, R S (1995). A Practical Guide to Ecological Management of the Golf Course. BIGGA & STRI.
Zahradník, J (1991). Bees, Wasps and Ants. Hamlyn, London.

Abbreviations
BC - Butterfly Conservation
EN – English Nature
EFC - Essex Field Club
GLA – Greater London Authority
ICT - Invertebrate Conservation Trust	LBP - London Biodiversity Partnership
LNHS - London Natural History Society
LWT – London Wildlife Trust
RPA - Royal Parks Agency	

Contact
The Lead for this habitat is the Royal Parks Agency.
Nigel Reeve
Royal Parks Agency
Holly Lodge
Richmond Park
London 	Tel  020 8948 3209
email nreeve@royalparks.gsi.gov.uk