Acid Grasslanda nationally important habitat in London

Lowland AcidGrasslandis an important habitat fornature conservation throughoutthe Greater London area.

Areas of infertile soil, unsuitablefor growing crops, were oftenused by our ancestors ascommon grazing land,supporting a mixture of heathand acid grassland rich inwildlife.

Today, some of these areasremain as commons andparklands, but the vast majorityhave been developed, convertedinto sports pitches and otheramenity grasslands, or theyhave been neglected andallowed to develop into scruband woodland.

The few remaining areas ofheath and acid grassland inLondon are now under seriousthreat – we need everyone tounderstand and support effortsto conserve this precioushabitat for the future.

In the UK there are manykinds of grassland, each withdifferent characteristicspecies of grasses, wildflowers and other wildlife.These differences depend onfactors like the nature of thesoil, altitude and land-use;both now and in the past.

Lowland acid grassland develops on low-nutrient, acidic soils (pH 4 to 5.5)overlying acidic rocks or on the free-draining, gravelly and sandy soils found in many parts of London. It often occurs as an integral part of lowlandheath landscapes, commons andparklands. Grazing (or cutting) is neededto prevent invasion by scrub and trees.

OTHER GRASSLAND TYPESOther types of grassland inLondon that are alsoimportant for wildlifeconservation include the‘chalk grassland’ found onalkaline (high pH) soils or onsoils of medium pH,wildflower-rich ‘neutralgrassland’. When eitherthese grasslands or acidgrassland are degraded bynutrient enrichment or badmanagement, so-called ‘rank’grassland develops. Thedelicate fine grasses andwild flowers are replaced bycoarse grasses likecocksfoot, rye grass, commoncouch, Yorkshire fog andother plants like thistles,common nettle, dock, broad-leaved plantain and rosebaywillowherb.

What is Acid Grassland?

Themain pictureshows acid

grassland in BushyPark with well-

developed ant hills.A diversity of grassesand wild flowers, such

as germander speedwell(blue) and heathbedstraw (white),

can be seen inspring.

Chalk grassland

Neutral grassland

Rank grassland

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Acid grassland is anationallyimportant habitat

l Lowland Acid Grassland is aUK Biodiversity Action Planhabitat and as such is a toppriority for wildlifeconservation nationally.

l Several plant, invertebrate andbird species found in acidgrassland are protected underthe Wildlife and CountrysideAct 1981.

l In England and Wales thereare 271 Sites of SpecialScientific Interest (SSSIs) thathave this habitat as a principalreason for notification.

l A number of Special Areas ofConservation (SAC) aredesignated under theEuropean Habitats Directive.These include Epping Forest,Wimbledon Common andRichmond Park, all of whichinclude substantial areas ofLondon’s acid grasslands.

Why is Acid Grassland important?

l In London there are an estimated 1,300hectares of lowland acid grassland, whichcontributes about 4% to the national resource.

l The acid grasslands of Greater London, southEssex and north west Kent are an importanthome for a distinctive community of insects andspiders – many of which are nationally scarce.This community is collectively known as the‘Thames Terrace Invertebrates’.

Wimbledon Common and Putney Heath (mainpicture) is a Site of Special Scientific Interestwhich supports the most extensive area of wetheathland in Greater London, with importantareas of dry heath and acid grassland.

Acid grasslandspecies you may seeinclude (clockwisefrom above): mat grass,wavy hair grass, heathspeedwell and Essexskipper butterfly

Insects inthe Thames Terrace Invertebrates

group include the bee-wolf wasp(above left) and many solitary beesand wasps. The bee above is feeding

on mouse-ear-hawkweed

Main photo © Nigel Reeve.Insets © Piers Eley and Nigel Reeve

Acid grasslands are important in London

If you look closely, you will see that acidgrassland contains a diversity of fine-leaved grasses. These include commonbent, red and sheep’s fescues, mat grassand others.Alongside the grasses growwild flowers like sheep’s sorrel, heathbedstraw, tormentil, harebell, bird’s foot,common stork’s-bill, heath milkwort andbird’s foot trefoil.

Nationally scarce plantsfound in London’s acidgrassland includeclustered clover,upright chickweedand autumn squill.

In areas that are lesswell drained, you will seetussocky grasses, along witha range of sedges and rushes. Onthe soil surface you may find a range ofmosses and lichens.

Acid grasslands are also important fortheir fungi, in particular variouscoloured waxcaps (below) – butconditions are rarely good enough for these in the London area.

Grasses and rushes, like dense-headed heath woodrush (left) aretypical of acid grassland. However, a huge range of tiny, yetspectacularly beautiful, wild flowers thrives in the acid grasslandhabitat. If you look carefully, you will often be rewarded byfinding delicate blooms like those on these pages.

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Introducing the plants of Acid Grassland

Heath milkwort

Harebell

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Waxcap fungi

Bird’s foot

Heath bedstra

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The infertile acidic soil meansthat the grasses and flowers aregenerally small and grow closeto the ground.

Patches of bare soil are veryimportant because they warmup quickly in the sun, which isgood for a range of insects,spiders and reptiles.

Although invasion by scrub andtrees is a serious threat to ouracid grassland, occasionalpatches of scrub, includinggorse and heather, addstructure and valuable diversityto the habitat – providingshelter as well as pollen andnectar for insects.

Grazing animals do a muchbetter job of maintaining anideal structure than the use of mowing machines.Theirtrampling and browsinghelps to control scrub andcreates a naturalpatchwork of plant heightsand bare areas.

Habitat structure

Wolf spiderwith her eggs

Dwarf gorse adds toacid grassland habitat

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Rabbits haveexposed theearth (below),providing awelcomingwarm-uppatch forcommonlizard (right)

© Susanne Blankemeyer

Common green grasshopper

Highland cattle (right) are hardy grazersthat control scrub and bracken, createstructure in the vegetation and help torestore grasslands

l Smallmammals

suchasshrews,mice and

voles (above right) forage in dense grass.

l Common lizards may bask in sun-warmed patches of bare soil.

l Kestrels (top left) and tawny owls(left) hunt many of these creaturesas prey.

l The large range ofinvertebrates attractsmany other birds suchas the greenwoodpecker, meadowpipit and skylark.

l In undisturbed areas,meadow ants createdistinctive mounds (anthills) among the grass(right).

l Characteristic butterflies include the smallheath, meadow brown, small copper, small,large and Essex skippers.

l The Thames Terrace Invertebrates includemany species of burrowing bees and wasps.The red-banded sand wasp is a flagship speciesfor acid grassland in London. The mining beeAndrena florea and the bee-wolf wasp areendangered and nationally scarce speciesfound in London’s acid grassland.

A huge array of animals can be found in acid grassland...

What animals might I see?Meadow brown (top left) and smallcopper (top right) butterflies, the bee-wolf wasp (below left) and manyspecies of tiny solitary bee are among acid grassland’s residents.

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The conservation of acidgrassland depends on appropriatemanagement and the co-operationof visitors to the sites. Neglectallows the habitat to becomeinvaded by scrub and woodlandso that it loses its special wildlifevalue.The addition of nutrients byfertilisers, dog-fouling or fromatmospheric pollution fromvehicles, are all very damaging; asis the use of lime either to‘improve’ the grassland or instone chippings used in car parksand paths.Tree planting, even justone tree in the wrong place, willincrease shade and can causesignificant destruction of thisvulnerable habitat.

An important aim of grasslandmanagement is to ensure acontinuity of cover and foodsupply for wildlife throughout theyear. For example, many insectsspend the winter as eggs orlarvae in standing dead plantstems. So it is vital never to cutor graze an entire area, but toleave a percentage untouched ineach parcel of land as a wildliferefuge.

Ideally acid grassland is maintainedby carefully-managed low-intensitygrazing with livestock; usually hardybreeds of cattle, sheep or ponies.However, if grazing is reallyimpractical, as it is in some urbanareas, a programme of cutting andscrub control is necessary.

The time of cutting is alsoimportant. A summer cut mayremove food from some insectspecies at a critical time. Cuttingbefore the end of July may alsoaffect ground nesting birds like

skylarks, meadow pipits and others.It is generally best to delay cuttingfor as long as possible into theautumn, although the availability ofthe appropriate machinery and wetweather may mean that timing hasto be flexible.Whenever the cutoccurs, it is best to remove all thecuttings to avoid putting thenutrients back into the soil.Sometimes an acid grassland orheath in poor condition requiresradical treatment such as majorscrub clearance, or the removal ofan area of secondary woodland.

What can we do to conserve it?

One effective remedial treatment is to scrape offan area of nutrient-enriched topsoil and eitherremove it, bury it or pile it into a bank. Ratherthan re-seed, the site is usually left bare torecolonise naturally, so the area may look a bitbare for a while.

The ground can look a bit ugly to the generalpublic and may lead to complaints. However, thebare ground will be colonised by specialistpioneer species, the acid grassland habitat willrecover to a better standard than before and thewildlife of the site will benefit greatly in thelong term.

Scraping a living for wildlife

Low-intensity grazing by hardy traditionalbreeds of livestock like Welsh ponies(above) and placid Longhorn cattle (below)is ideal for acid grassland wildlife.

The area above was scraped clear of rich topsoil(above). Seventeen months later, the ground wasbeing re-colonised by pioneering acid grasslandplants and animals (left).

All photos © Nigel Reeve.

l Always observe the bylaws ofthe sites you visit and respectthe needs of wildlife and othervisitors.

l Please clear up after your dog– otherwise you are addingnutrients to the soil and theseencourage the growth ofcoarse grasses, dominantweedy plants and eventually

will allow scrub to take over.l Please do not drop matches

or have a barbeque on thesegrassland sites. They are veryeasy to set fire to in dryweather and burning is verydamaging.

l Please keep to pathways.Moving off paths can result inthe trampling of many of the

creatures we are trying toconserve.

l Please avoid disturbing wildlifeand do not pick, uproot ordamage plants and fungi.

l Support land managerscarrying out conservationmanagement, whether this isbringing-in grazing, mowing,scraping, scrub clearance or

removing trees that arethreatening the habitat.

l Why not enquire aboutconservation volunteering?There may be opportunities tojoin in with everything frompractical land managementwork to helping witheducation and interpretation.

London’s Acid Grassland Habitat Action PlanThe London Biodiversity Partnership (LBP) was established in 1996in response to the UK Biodiversity Action Plan. The LBP aims toprotect and enhance the capital's habitats and species for the benefitand enjoyment of future generations. There are now 31 action plans:11 habitats, 12 species, plus 8 Generic Action Plans that address broader issues. Each action plantackles key issues such as conservation and education and is implemented by a working groupmade up of a partnership of public, private and voluntary organisations and also individualenthusiasts.

The Acid Grassland Habitat Action Plan Working Group works alongside other action plans forheathland, chalk grassland, reptiles and others. Our main aims are:• 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 theinvolvement of Londoners in its conservation.

Biodiversity

Want to know more?l Ask your site manager about

whether there are any nature-trailor information leaflets, guidedwalks or talks you can attend sothat you can learn more aboutacid grassland, adding to yourenjoyment of the sites you visit.

l Use the internet to visitwww.lbp.org.uk to see the fullacid grassland biodiversity actionplan for London.You can alsodownload an advisory bookletAcid Grassland Conservation inLondon (2005) containing moredetailed guidance for landmanagers.

l Visit www.ukbap.org.uk to seethe national plans for acidgrassland (upland and lowland).

l Visit the London Wildweb websitefor detailed information onwildlife sites in London.http://wildweb.london.gov.uk

How you can help – a user’s guide

All photos © Nigel Reeve.

Main picture: Hounslow Heath is an extensivearea of acid and neutral grassland. Heathland isdeveloping where restoration has encouragednatural regeneration of heather. It is home tomany other special plants and animals that needheathland and acid grassland to survive in.Among the common species you may see are thefield grasshopper (above) and six-spot burnetmoth (below).

Twenty seven London Boroughs out of 33 have some acid grassland.Some key sites for acid grassland conservation in London

that you can visit are listed here.

M40

M4

M3

M25

M23

M25

M1

M11

M20

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Chislehurst Common,Bromley.Contact:ChislehurstCommonsConservators,01689 825102

Hadley Green, Barnet.Contact: London Boroughof Barnet GreenspacesTeam, 020 8359 7825

Hounslow Heath,Hounslow.Contact: CIP Group,020 8577 3664

Mitcham Common,Merton.Contact: MitchamCommon Conservators,020 8288 0453

Poor’s Field, Ruislip WoodsNational Nature Reserve, Ruislip.Contact: London Borough of Hillingdon, 01895 250635

Wanstead Flats,Redbridge.Contact: City of London,020 8508 0028

Wimbledon Common,Wandsworth and Merton.Contact:Wimbledon &Putney CommonsConservators,020 8788 7655

Richmond ParkNational NatureReserve,Richmond upon Thames.Contact:The RoyalParks, 020 8948 3209

Bushy Park Richmond upon Thames.Contact:The RoyalParks, 020 8979 1586

Some Acid Grassland sites you can visit in Greater London

Published by the LondonBiodiversity Partnership.Booklet funded by English Nature.The Royal Parks are the leadpartner for the London AcidGrassland Plan.

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Map not to scale.Position of sitesapproximate