Geology and biodiversity- making the links

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Front cover photographs:Top left: Slade Brook, Gloucestershire. Roger Meade/English NatureMiddle left: Moorland. Michael Murphy/English NatureBottom left: Stanground brickpit, Cambridgeshire. Peter Wakely/English Nature 14,727Main: Cornwall rock. Michael Murphy/English Nature

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Geology and biodiversity-making the links

3Geology and biodiversity - making the links2

Geology and biodiversity-making the links

These landscapes hold a diversityof habitats and species, specialthroughout Europe. We havewoodlands and heathlands, chalkgrassland, rivers, fens and bogs.But why do we have such varietyin such a small space? Theanswer lies in the diversity of theunderlying geology.

For all living organisms, includinghumans, our environment affectsthe way we can live and theresources available to us. Thisenvironment is fundamentally aresult of climate (rainfall, lightand temperature), the physicallandscape(slope, aspect andaltitude), and substrate. Thecombination of these factors, plusthe interactions of the livingorganismspresent in thatenvironment, is the ecosystem.

Geology is a critical factor. Itinfluences climate at global,regional and local scales.Landscape is determined by thenature of the rocks that lie beneaththe surface and the processes thathave shaped and formed them.Substrate and soil are closelyrelated to the nature of the rocksfrom which they are derived.

When working with ecosystems,we need to take a holisticapproach in understanding thegeology, the wildlife and how theyinteract to shape the ecosystem.

Past ecosystems

Since the Earth was formed 4,600million years ago it has neverstood still. Plate tectonics (themovement of the Earth’s crust) hasbrought continents together andpulled them apart. This hascontinuously changed the patternof land, ocean and climate and hasalso driven evolution, extinctionand an ever-changing pattern ofecosystems.

Britain vividly illustrates thisdynamic Earth. Our oldest rocksare 2,800 million years old. Sincethe Cambrian (approximately 500million years ago), platemovement has carried Britainfrom 30 degrees south of theequator to its present position.Britain’s rocks record the vastchanges of climate andenvironment as Britain haschanged from land to sea, andfrom tropical to temperate toglacial.

The landscapes of England

are hugely varied. There are

the lakes and mountains of

Cumbria, the rugged spine of

the Pennines, the limestone

dales of the Peak District and

Yorkshire, the rolling chalk

downs of Wiltshire and the

Chilterns, and the flat

expanses of the Fens. The

coastline ranges from the

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Crinoid fossils, Salthill and Bellmanpark Quarry SSSI,Clitheroe, Lancashire. Peter Wakely/English Nature 7,317

Peak Cavern and Peveril Castle, Castleton, Derbyshire. Anna Wetherell

Carboniferous (354-290 million years ago)

Carboniferous rocks are a recordof equatorial environments andchanging sea levels. Initially,under a warm, tropical sea extensive reefs of crinoids andcorals developed. As the sea level dropped, rivers brought insands and silts from the land areas, forming vast sandy deltas.On top of the deltas thick swamp vegetation developed, includingtrees, ferns and horsetails.

Today the Carboniferous rocksshow this change. The earlytropical limestones outcrop widely, forming the Mendip Hills,the Avon Gorge, the Derbyshire

Peak District and the YorkshireDales. Thick deltaic and riverinesandstone forms the overlyingMillstone Grit in the Midlands and northern England, whilst theswampy vegetation was compressed to form the coalseams of the adjacent, low-lyingUpper Carboniferous CoalMeasures.

Just as importantly, this range of rocks provides a substrate fora range of habitats. TheCarboniferous limestones of thePeak District, Yorkshire Dales and the Mendips support limestone grasslands and form anetwork of karst and caves, andthe Millstone Grit underlies the moorlands of the Pennines.


Valley of Stones NNR, Dorset. Peter Wakely/English Nature 21,939

Woolly rhino skeleton found at Whitemoor Haye,Alrewas, Staffordshire. Field Archeology Unit,Birmingham University

Quaternary (1.8 million years ago to present)

The most recent major climaticchange has been the last Ice Age.Around 2.5 million years ago, the Earth became colder and iceexpanded from the poles. Northern Europe experiencedrapid changes in climate. Therewere significant, cyclic fluctuationsbetween colder temperatures when the ice advanced (glacials),and a warmer, more temperate climate (interglacials). Much ofBritain was periodically coveredwith glaciers and, beyond the ice, tundra and permafrost.

The ice scraped off any soil which had developed, leavingsculpted bare rock, or depositingclays, sands and gravels in itsplace in glacial landforms. Whatsoil was left blew around thefrozen landscape, forming depositsknown as loess. Rivers carriedglacial meltwaters, depositingmassive amounts of sediment inthe sea and on land. River coursesdeveloped and changed as iceadvanced and retreated leavingcomplex river terraces. As sealevels rose and fell, coastlinesmoved back and forth.

Left: St Bees Head, Cumbria. Peter Wakely/English Nature 21,304

Magnesian limestone, Cassop Vale NNR, Durham. Peter Wakely/English Nature 21,224

Permian and Triassic (290-205 million years ago)

Hot, arid desert conditionsdominated the Permian andTriassic. Extensive red sandstonesand mudstones were deposited,which now form the characteristicred rocks of the south coastbetween Exmouth and Sidmouth,the low-lying ground and linearridges of the Cheshire Plains and the red sandstone cliffs of St Bees Head in Cumbria.Shallow seas existed in north east England during the Permian, containing limestone reefs whichnow form the north-southMagnesian Limestone escarpment.The evaporation of the seawaterchanged the limestone todolomite, making it rich in magnesium rather than calcium.

Now the sandstones provide anopportunity for heathland to flourish in Cheshire and the Wirral,and underlie the rich pastures ofCheshire and Warwickshire.Magnesian limestone grasslandoccurs only where the Permianevaporating seas once were.

also from changes in atmosphericcomposition, the circulation ofocean currents and the rise andfall of sea level. Geology teachesus just how interlinked and interdependent the environmentand ecosystems are on Earth.

Understanding this interdependence is essential tounderstanding how and why ourenvironment is changing. Ourenvironment has changed in thepast and is continuing to change.Ecosystems react to this and provide a feedback loop into it. In this present period of climatechange, part driven by our owninteraction with our environment,such knowledge can guide us howto work within this.

The major expanse of ice meantthat sea levels dropped and Britainwas connected to mainlandEurope. Woolly mammoth andwoolly rhino lived here, alongwith hyena, deer and bears. Manalso arrived. Changing climates,the gradual recolonisation byplants, the changing fauna, and the impacts of man, are all shown in pollen and sedimentrecords, often found in peat bogsor lakes. A major impact of theice was that much of Britain was literally ‘scraped clean’. The landscape and environmentwe know today has really onlyevolved over the last 10,000 years or so.

Many of these ancient ecosystemssound familiar from environmentstoday, and indeed geologicalinterpretation develops fromunderstanding modern-dayecosystems. Geology is stronglyrooted in both the present and thepast. We can learn much from thepast for the future, especially aboutthe impacts of climate change.Therock record shows that changes inclimate occur not only as a resultof the movement of continentsaround the planet, for exampleBritain’s progress northwards, but


Fens under snow near Holme Fen NNR, Cambridgeshire. Peter Wakely/English Nature 11,342

Derwent Water, Lake District, Cumbria. Paul Glendell/English Nature 23,075A

Substrate is also fundamental to anecosystem and comprises theunderlying rock or soil, in whichthe plants grow. In terrestrialecosystems, the plants are thefoundation of the food chain.Substrate is therefore the foundation of life.

Soil derives from rock. As rockbreaks down through weatheringand erosion, the resulting particlesform the basis for soil. Soilevolves as a result of physical and chemical processes, and biological activity. It can varyfrom a very thin cover, or none, to deep soils and peat. The sourcematerial is important in determiningthe chemical and physical natureof the developing soil. Chalks andlimestones lead to an alkaline, usually well-drainedsoil; sandstones, sands and gravels leadto an acidic, well-drained soil;while finely-grained rocks, such asclays, mudstones and shales, canlead to a poorly-drained soil.

These variations in substrate are the foundation for the diversity of habitats and speciesthat have developed in England.They reflect the diverse geology, geomorphology andresultant landscape that we seearound us.

Present-day ecosystems

Ecosystems result from theinteraction of climate, physicallandscape, substrate and livingorganisms. They develop atvarious scales. The planet can beregarded as an ecosystem, as can awoodland, a peat bog or a rockpool.

Rocks determine landscape in anumber of ways. Harder rockserode less easily than softer ones,leaving the harder rocks standingout in the landscape. Theprocesses of plate tectonics canfold rocks. This process has led,for example, to the pattern oflandscape seen in the Weald andthe spectacular landscape of theLake District. Weathering anderosion shape the rocks, whetherdue to wind, rain or ice. Themountains of Scotland would haveonce stood as high as the Alps, but millions of years of erosionhave softened the landscapeconsiderably.

Variations in landscape affectclimate and weather. On a globalscale, the distribution of land andocean, and the changing height ofthe land, controls the way air circulates around the planet. This

Deepdale Meadows SSSI, North Yorkshire. Peter Wakely/English Nature 19,667

is a key influence on global climate.At a local scale, the geology canaffect regional weatherpatterns.For example, the Pennine ridgethat runs through England forcesair to rise over it, which causeswater to condense, form cloudsand fall as rain. As a result, thenorth west of England is generallywetter than the east, which broadlyinfluences the development ofecosystems. Most of our peat bogsoccur in the north west because ofthis difference in climate.

9Geology and biodiversity - making the links

Serpentine

Serpentine broadly describesrocks, minerals and soil associatedwith metamorphosed ultramafic(low silicate content) rocks containing serpentine-group minerals. Soils derived from serpentine-rich rocks are high iniron and magnesium, low in calcium, phosphorus, potassiumand molybdenum. They may alsobe high in nickel, chromium, manganese and cobalt and canproduce a range of soil typeswhich vary according to parentrock, weathering, relief and biological processes.

In Britain, serpentinised rocks areuncommon. One of the bestknown outcrops is the serpentinisedperidotite of The Lizard ophiolitein south west Cornwall, whichwas part of the oceanic crust inmid-Devonian times (around 375million years ago).

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is restricted to the chalk, breedingin open chalk grassland. Its foodplant, sheep’s-fescue Festuca ovina,is widely distributed. However,only south-facing (and grazed)chalk slopes provide the warmmicroclimate and short turf neededfor its larvae and pupae todevelop.

Chalk

During the Upper Cretaceous(95-65 million years ago) anextensive, shallow sea coveredmuch of Britain and deposited athick, pure limestone known aschalk. The chalk today characterises the rolling hills ofthe South and North Downs, theChilterns and the Lincolnshire and Yorkshire Wolds, and supportsa characteristic calcareous flora.

A number of features of the rock,including porosity and softness,influence chalk landscapes andtheir ecosystems. High porosityproduces a flora dominated byperennials with relatively deeproot systems and low-growingplants specifically adapted tocalcareous, arid and nutrientdeficient conditions (eg autumngentian Gentianella amarellaandthe hairy violet Viola hirta).Beech Fagus sylvaticawoodlandis also intimately (though notexclusively) associated with chalk.Well-known sites include thebeech woods of the Chilterns, eastHampshire and the North Downs.

Mole Gap SSSI with regenerated escarpment, Surrey. Herb rich National Trust grassland. Peter Wakely/English Nature 21,305 Erica vagans, Ulex gallii, Goonhilly Downs SSSI. The Lizard NNR. Peter Wakely/English Nature 10,798

In detail, the woodland communitychanges as slopes become steeper,from relatively deep, moist and base-rich soils to the thin, dry andstrongly base-rich soils of steepslopes.

In England the silver spotted skipper butterfly Hesperia comma

Much of The Lizard is underlainby serpentinite and the vegetationis broadly described as heathland.Plants are typical of dry acid heath but include the rare Cornish heath, which is the mostabundant heather here. What isunusual is the presence of typicalchalk- or lime-loving speciesincluding common dropwortFilipendula vulgarisand bloodycrane’s-bill Geranium sanguineum.This relationship is not understoodin detail but it is possible thatsome species found on The Lizard may have evolved local adaptations to the unusualconditions associated with thecomplex geology of the peninsula.The occurrence inland of typicallycoastal species (for example thriftArmeria maritimaand sea campion Silene uniflora) alsoreflects the chemical similaritiesbetween seawater and serpentinesoils.

Predannock Downs, The Lizard NNR, Cornwall. Peter Wakely/English Nature 15,803

Hairy violet Viola hirta, Surrey. Peter Wakely/English Nature18,828


Future ecosystems

The UK has set itself challengingtargets for maintaining andrestoring habitats and speciesacross the UK through the UKBiodiversity Action Plan(UKBAP). Government also hastargets relating to the condition ofSites of Special Scientific Interest.Can we use the links betweenbiodiversity and geodiversity toachieve these targets and help withunderstanding ecosystems?Within the nature conservationfield it often appears that geologyand biology are two completelydifferent subjects. However,bringing the two together haspractical benefits.

The links between geology andbiology can be used as amanagement tool, as a way ofdesigning surveys, or as ananalytical method. We can mapchanges in the geology or soil type

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Sugar limestone on Widdybank Fell. Moor House - Upper Teesdale NNR, County Durham. Peter Wakely/English Nature 14,155

Sugar limestone

Found in Upper Teesdale, CountyDurham, the ‘sugar limestone’ is athin bed of limestone that wasmetamorphosed into a coarselycrystalline marble by the intrusionof the Whin Sill dolerite. Therock weathers extremely slowlyinto a thin, drought-prone soil,with a grain size similar togranulated sugar.

The sugar limestone supports aspecies-rich grassland dominatedby blue moor-grass Sesleria

albicansand includes twosub-communities found only inUpper Teesdale. It supports oneof the richest groups of rarespecies in Britain including springgentian Gentiana vernaandTeesdale pansy Viola rupestris.Some of the more unusual plantcommunities occur where streams(or ‘sikes’) have weathered thelimestone to hard crusts andunstable gravels which in placesproduce moss hummocks. This isthe only place in Britain whereTeesdale sandwort Minuartiastricta grows.

At all scales, differences ingeology and landscape lead tovariations in climate. In turn thisinfluences global weather patterns,regional rain patterns andmicroclimate. For example,north-facing slopes tend to receiveless sunlight and warmth. Similarvariations influence soil type andlead to differences within habitats.All this combines to createmosaics of habitats, opportunitiesfor a diverse range of plant andanimal species and the complexrange of ecosystems we seearound us today.

Man’s influence is a significantadditional influence on ecosystems in England. Landmanagement, for example in theform of agriculture, grazing andwoodland management, have allhad significant impacts on thediversity of habitats and speciesfound here. Heathlands andgrasslands are unlikely to survivewithout management, as theyoften develop naturally into scruband woodland. Our demands forwater have a significant impact onhydrological systems, and thus thewater available within ecosystems.The development of industry hasincreased levels of pollution in theair, water and on land, and theavailability of artificial fertilisersand pesticides.

None of this is static. As the Earth has changed over millions of years so the landscape aroundus continues to evolve.Geomorphological processescontinue to act on our landscapethrough weathering, landmovements, rivers and coastalprocesses, even sometimesearthquakes. Working withecosystems involves appreciatingthe diversity of nature, but alsoaccepting change. We may havea significant influence, butultimately we cannot controlnatural processes. We are alsofacing global climate change,largely induced by our ownactivities.

Shore dock Rumex rupestris, Cornwall. Peter Wakely/English Nature 18,105

Searching for the shore dock

Shore dock Rumex rupestrisis ascarce plant found generally in thesouth west, on beaches wheresediments known as ‘head’ or ‘till’meet the beach, often with a flushor seepage. Using this knowledgeand geological maps, possible newsites were identified. Designingthe next season’s survey tookthese possible locations intoaccount, with great success. As aresult, the known population ofshore dock in the south westincreased by 30%. This methodcan be used widely, to identifysuitable habitats for survey, forrelocation or for re-creation of arange of potential habitats andspecies.

along with the vegetation.Changes in substrate, or inhydrology can answer questionsabout the distribution of habitatsand species. When consideringmanagement techniques,particularly when relating toaltering practices, taking geology,substrate and hydrology intoaccount can predict results moreaccurately.

For species with well-knownrequirements, links with substrateand hydrology can be a useful toolfor focusing surveys where thedistribution is uncertain.Geological maps exist at a rangeof scales, covering both solid(pre-Quaternary) and drift(Quaternary/recent) deposits.Along with soil maps, when theseare combined with detailedknowledge of potential habitat andspecies requirements, they canprovide an excellent tool forplanning survey and management.

Millstone Grit ‘sculpture’ near Hathersage in the Peak District. Paul Glendell/English Nature 24,063


Water management –understanding geology tomanage biology

When managing wetland sites,both permanent and ephemeral,understanding the catchmentdynamics and the interactionbetween groundwater, bedrock andsuperficial deposits is extremelyimportant.

Water alkalinity is a key aspectinfluencing the biology of riversand streams. Understanding thegeology and geomorphology of awatershed can help to predictalkalinity. Watersheds withgranitic bedrock have low alkalinity,whilst those with calcareous sedimentary bedrocks have highalkalinity. The chemistry ofextensive river systems, such asthe River Tweed in northernEngland and Scotland, changes asthe underlying geology changes.The plants and animals living inthe river will vary according to thedifferent environmental conditions.

Base-rich lakes and water bodiesare usually confined to calcareous

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Importantly, the management ofgeological sites benefitsbiodiversity. In coastal and riverenvironments the best geologicalmanagement is to maintain naturalprocesses. This non-interventionshould maintain a natural habitatsuccession. Inland, typical management of geological sitesinvolves removing or redistributingscree and clearing vegetation toprovide a mix of bare rock, openground and habitat mosaic.

There is, however, a poor understanding of the biodiversityof geological sites or the geodiversity of biological sites.Nevertheless, it is clear that disused quarries, for example,offer a refuge and diversity ofhabitat for both specialist and non-specialist species. This is

Managing geodiversity andbiodiversity together

Geological sites are important fortheir biodiversity. There are veryspecific relationships, such as thestrong link between exposed rocksurfaces and lichens, or betweenrare metallophyte plants and minedump spoil. There are also otherbroad relationships, such as thebenefit that bare ground and rocksurfaces bring to a range ofinvertebrates or simply as nestingsites for birds.

Tufa dams, Slade Brook, Gloucestershire. Roger Meade/English Nature

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environments, which are normallyfree-draining – so standing wateris rare here. The Jurassic OxfordClay, however, is relativelycalcareous and brick pits, such asOrton Pit near Peterborough, canprovide extensive alkaline pondsystems. The Orton Pit supportsten charophyte (stonewort) speciesincluding the main Englishpopulation of the beardedstonewort Chara canescens. Thisearly coloniser of ponds prefersslightly brackish conditions whichare produced by the release ofsalts contained within the OxfordClay. This site also holds a large

population of great crested newtsTriturus cristatus.

Karst (limestone surface features)and caves have a specifichydrology, where water mainlyflows underground. Complexlinks exist between areas ofdrainage and re-emergence.Streams flowing out of limestonesystems are usually saturated incalcium carbonate, creatingspecialised habitats such as tufasprings. Caves themselvesprovide an additional habitatimportant for a range of species,including bats.

Lichens on sarsen, Fyfield Down NNR, Wiltshire. Peter Wakely/English Nature 11,633

reflected in the number of disusedquarries identified as important fortheir biodiversity.

It is important that a wider view of‘site management’ is taken. Whenestablishing management plans forgeological sites it is important toincorporate the biodiversity gainthat can be achieved. Equally,management of biological sitesshould consider the potential benefits for geology. The principle is simple, and can bringwide benefits.

Rock face, Hulme Quarry NNR, Staffordshire. Paul Glendell/English Nature 25,999

Tufa deposits, Slade Brook, Gloucestershire. Roger Meade/English Nature


Further reading

ELLIS, N.V., BOWEN, D.Q., CAMPBELL, S., and others. 1996. An introduction to the Geological ConservationReview. Geological Conservation Review Series No. 1. Peterborough: Joint Nature Conservation Committee.

ENGLISH NATURE. 2003. Learning from the past to influence the future. Peterborough: English Nature ResearchReport, No. 502.

ENGLISH NATURE. 2004. Geological conservation benefits for biodiversity. Peterborough: English Nature ResearchReport, No. 561.

ENGLISH NATURE. 2004. Linking geology and biodiversity. Peterborough: English Nature Research Report, No. 562.

HOPKINS, J.J. 2003. Some aspects of geology and the British flora.British Wildlife, 14(3), pp. 186-194.

OPEN UNIVERSITY - Earth and Life (S269) course books.

YALDEN, D.W. 2003. Mammals in Britain – a historical perspective. British Wildlife14(4) pp. 243-251

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Bringing together several layers ofdata can help to identify patternsand make links between geology,biodiversity and landscape.Landscape-scale projects can helpto protect individual sites, such asSSSIs, by providing buffer zonesfor sensitive habitats. Peatlands,for example, will often need careful water level management of the surrounding land to ensurethat water levels are maintainedwithin the site. Species can alsobenefit from landscape-scale projects, through corridors andpathways which allow populationsto expand and move around. BAP

targets can only be met by understanding the ecosystemswhich support the individual habitats and species.

Geological maps, soil maps anddistribution of vegetation are alluseful tools in working withecosystems. Now we have astrong series of specialist bases,we need to learn to bring thosespecialisms together, to achievethe goals of conserving both biodiversity and geodiversity.

There are many opportunities touse this holistic approach. EnglishNature developed the frameworkof Natural Areas, which link to theCharacter Areas developed by theCountryside Commission (nowCountryside Agency). These lookat landscape-scale characteristicsof geology and habitats, and canbe used to develop broad objectives for biodiversity and toidentify regional issues. NaturalAreas are useful for identifyingwhich areas are important forwhich habitats and species, andare, unsurprisingly, closely linkedto the underlying geology.

Cornwall rock. Michael Murphy/English Nature

Key messages• England’s geology is extremely diverse. It illustrates a continuously changing past over hundreds of

millions of years. Changing climate, evolving life, rising and falling sea, mountain building, earthquakes and volcanoes are all part of this geological history.

• Geology directly influences the character of our landscape, habitats and species. This diverse and dynamic geological past has produced the diversity of landscape we see around us. There is a direct relationship between geodiversity and biodiversity.

• Geology influences climate. The global pattern of continents, a consequence of plate tectonics, influences global weather, mountain chains affect regional weather patterns and aspect can determine microclimate.

• Geology directly influences substrate. Soil is derived from underlying parent rock and directly reflects the physical nature and chemistry of local and regional geology.

• Geology is crucial to the way ecosystems function. Ecosystems result from the interaction of climate, physical landscape, substrate and living organisms. Geology influences all these factors.

• To fully understand ecosystems and better manage our environment it is essential that we integrate the way we work and think. We must bring together our understanding of geodiversity and biodiversity.

• Geology tells us how our environment has changed and reacted to change. It is important to understand this to better prepare for future change.

• Bringing geodiversity and biodiversity together can help us better understand the environment around usand how to work with this changing environment.

• Managing geodiversity and biodiversity together is mutually beneficial. Many geological places are important for biodiversity and many places important for their habitats and species have geological value.

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Geology and biodiversity- making the links