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It is easy for conservationists to understand how to maintain pristine habitats such as the Antarctic; they just need to be left undisturbed. But conservationsists rarely deal with such habitats. Most woods, meadows, fens, bodies of water or heaths have been much influenced by people. Simply leaving such habitats alone is rarely the best approach.

These semi-natural communities often require careful management – but is often not obvious which polices are best. An understanding of the history of a habitat can give us enormous insight into its requirements, and help to settle disputes among conservationists about how it should be treated. As an example of the importance of this historical knowledge, we take the Breckland heaths in East Anglia.

Lowland heath is an internationally threatened habitat and England contains a significant fraction of the heathland left in the world. One of the most famous examples of heath in Britain is Breckland, which lies on the border of the counties of Norfolk, Suffolk and Cambridgeshire. It has long been recognised as a site for rare birds, plants and insects, and an important historical site dating back to Neolithic times. Our recent research has revealed that much of the ecological interest has gradually disappeared, even on the heath’s nature reserves.

For most of recorded history, the 940 square kilometres of Breckland have consisted of vast tracts of thinly populated heathland. In the 17th century, travellers on the sandy trackways crossing this wild and treeless area wrote vivid accounts of their experiences: ‘Nothing was to be seen on either side but sand and scattered vegetation; a mere African desert. In some places this sandy waste occupied the whole scope of the eye. In many places we saw the sand even driven into ridges, and the road totally covered.’

In 1668 sands blown from Lakenheath Warren almost engulfed the village of Santon Downham 6 miles away and temporarily blocked the Little Ouse. Even in 1819 one writer described Breckland as ‘the geat expanse of heath and unenclosed land strip of every timber tree.’ Great bustards, red kites and ravens persisted in the area well into the 19th century.

One reason for the characteristic habitat of Breckland is that the climate is semi-continental. Breckland tends to have hotter drier summers compard with the milder maritime climate of the rest of the southern half of Britain, but the temperature varies considerably, with frosts possible in every month of the year. Breckland soils range from chalk rubble to acidic podsols, but are generally sandy, free-draining and among the least fertile in England. This combination of harsh climate and poor soils has greatly influenced both the vegetation and land use of the area.

Plants now found in the Steppes and Mediterranean were widespread in Britain in the warm dry period after the last ice age. They were generally lost as deciduous woodland developed, but in the more continental climate of Breckland many of these plant species have survived. A number of rare plants and insects of coastal sand dunes are also found on the sandy Breckland heaths. Although lowland heaths are found elsewhere in southern Britain, the fascinating mixture of rare Steppes, Mediterranean and coastal species makes the Breckland grass heaths unique.

Although geology and climate are clearly important, much of what is interesting about Breckland is a consequence of human activity. Early stone-age hunter-gatherers occupied the region and may have burnt areas of woodland to attract deer to the subsequent regrowth. When Neolithic agriculturalists came to Britain more than 5000 years ago, Breckland was one of the first areas they colonised. The open discontinuous woodland and sandy soils would have been the area easy to clear and cultivate compared with the dense oak and alder woods on the surrounding heavier soils.

The Neolithic people also brought grazing animals across the North Sea to Breckland. The grazing of these sheep, goats and cattle prevented the cleared woods from re-establishing – so the heathlands and bleak open landscape were created by the Neolithic people. Archaeological finds and documentary evidence show that grazing of sheep on these heaths continued from Neolithic times to the past century.

For the past 900 years much of Breckland has been heavily grazed by rabbits. The rabbit was introduced by the Normans and was originally kept within warrens for the production of meat and fur. The rabbits were a valuable and heavily protected crop – in 1813 a man was sentenced to seven years transportation for taking a single rabbit from a warren. The rabbits in these warrens were intensively managed: predators were controlled and food was often provided in harsh winters and during droughts, as at Thetford Warren where six teams of horses were used to cart food for the rabbits in winter.

From the 12th century the overgrazing by these huge populations of rabbits, combined with their scraping and burrowing, often led to the development of sand blow-outs. In 1809 the soil of one warren was reduced by the wind by nearly a foot, and part of Lakenheath Warren was still covered in sand dunes up to 1 kilometre wide and 6 metres high in the 1930s.

In rabbit warrens the combination of intensive grazing and disturbance favours mosses, lichens and annual plants. Early researchers realised that many of the rare Breckland plants require open, disturbed soil in which to germinate and become established and are eventually lost if the habitat changes to a closed grassland. Thus some of the declining rarities, such as Breckland thyme and spring speedwell, benefit from the rabbit activity.

The Breckland heaths have been intermittently farmed ever since being cleared by Neolithic people. A shifting pattern of agricuture was adopted, with areas of heath cultivated for a few years until the soil was exhausted. These patches were then abandoned and allowed to revert to heathland, while further areas were ploughed up. The term breck applies to such areas of grass heath which were briefly cultivated every 12 to 15 years, and has given the area its name. The total area cultivated was larger when the price of corn was high. During recessions, as when the Black Death reduced the population of Britain by a third, arable land was abandoned.

The cultivation of crops on the heathlands was hazardous. The soils were inherently infertile, rainfall was low and erosion of the soil by wind and sandstorms was a serious threat. As recently as 1918 the wind blew bushels of turnips out of the ground on one farm and practically ruined the crop. When asked at Bury market where his farm was, one farmer is said have replied: ‘Sometimes in Norfolk and sometimes in Suffolk, it depends which way the wind blows.’

In the late 18th century the prevalent philosophy of agricultural improvement and the incentive of high corn prices spurred large landowners in Breckland to enclose and cultivate heathlands. However, the yields obtained were very poor and by the mid-19th century it was realised that the experiment had been an expensive disaster. Many newly created brecks were abandoned and numerous farms went back to relying on rabbits as their main crop. One observer in 1883 write: ‘These blowing sands are extremely difficult to turf over, and it will be many years before they will produce the hard coarse herbage which formerly fed so many sheep and rabbits.’

In the early 1990s the area of heathland was greater than a century earlier. The many stony brecks with their impoverished soil were covered with annuals and ruderal plants, contrasting with the ancient heathlands with their mixture of bracken, heather, grass and lichen heath. Ringed plover, a bird of shingle beaches, nested in large numbers on these flint covered brecks. However this unusual ‘breck’ habitat is now rare in heaths in the area.

During the depression after the First World War the government began a massive programme of afforestation of these heaths and brecks. More than 20,000 hectares of land are currently covered by Forestry Commission plantations with additional large areas of private plantations. From the 1930s the increasing mechanisation of agriculture and intensive use of techniques to enrich soil fertility allowed the permanent conversion of heathland to productive arable land. After the Second World War, government policies further encouraged this expansion of arable agriculture. This intensive agriculture is very different from the low intensity traditional use of the brecks. The combination of afforestation and conversion to arable has massively reduced and fragmented the area of heathland remaining in Breckland. On one 9000-hectare estate the area of heathland had declined from approximately 64 per cent of the estate in the 1920s, to only about 10 per cent by the late 1950s, with further losses continuing into the 1970s.

In addition to the loss and framentation of heaths, there have been worrying decreases in most of the characteristic species in the remaining heaths, even on nature reserves. Wheatears nest on the heaths grazed by rabbits, and 689 pairs were recorded on the Suffolk Breckland in 1949. Half of these heaths have been lost; however, the remaining heaths on which 321 pairs were breeding held only 11 pairs in 1988. Woodlarks and ringed plovers once nested widely on the warrens, heaths and brecks but after a lingering decline finally ceased breeding in 1979 respectively. The stone curlew is the bird most birdwatchers associate with Breckland, yet the heaths have become less important to this species with each year, and surveys carried out by the Royal Society for the Protection of Birds have shown that most of them now nest on arable land.

A similar pattern of loss was found when we analysed the information on rare breckland plants. Many of thse species, for which Breckland is famous, were more widely spread in previous centuries. During this century most of the classic species have become extinct in more than half of the remaining sites of heath. The spiked speedwell has disappeared from seven of its nine sites while perennial knawel has been lost from 13 of its 14 heathland sites. In addition, consideration of the number of sites at which a species remains masks the full extent of the decrease. Descriptions of plant sites up to the 1920s show that many rarities once extended over many thousands of square metres, with more than 1000 plants of spiked speedwell at one site and Spanish catchfly growing ‘like a haycrop’ at others. Now, many of the remaining sites for such rarities consist of just a few, or a few tens, of individual plants in a very restricted area.

These declines in birds and plants have been so severe that on some sites protected as sites of special scientific interest or nature reserves many of the rarities originally occurring have disappeared, and it could even be questioned whether the continuation of the sites’ status is justified. Why should there be these changes in the characteristic species? It is clear that this is linked to major changes in the habitat of the Breckland heaths. We compared vegetation surveys taken nine years ago on a number of different sites with the vegetation present now, and found a trend, with lichens, annuals and bare ground being replaced by a community of perennials and rank grasses. The vegetation has thus changed from being sparse and patchy to relatively lush. The major reasons for these changes seem to be: the change in land management away from shifting cultivation, decreased grazing by stock, the decline of rabbit numbers, reduction in physical disturbance and enrichment by increased nutrients in rainfall.

Farewell to the lowly lichen and moss

An obvious interpretation of these patterns is that it is simple ecological succession – the natural progression of plant communities in time as colonising species give way to ‘mature’ assemblages of organisms. In the past a combination of grazing and disturbance meant that the vegetation on brecks, dunes and warrens was dominated by mosses, lichens, ephemeral annuals and ruderal plants. Stone curlews, ringed plovers, wheatears and woodlarks flourished in such an environment. But in many areas now ungrazed for decades, scrub and woodland is well developed. Even on some heaths which are still grazed by sheep, characteristic lichen heath is being replaced by a closed sward of perennials and rank grasses, which is unsuitable for these birds.

Ironically, many of the prime areas of heathland are on previously disturbed habitat. The Breckland heaths have always experienced a shifting mosaic of disturbance, with trackways linking numerous brecks, marlpits and chalkpits. Annual plants and various rare Breckland species once grew in such pits and on the numerous sandy trackways crossing the heath. Rabbit warrens were enclosed by turf walls capped with gorse. It has been estimated that 25 square metres of turf were required to construct one metre length of wall. These boundary walls were extensive (Thetford Warren’s boundary was 8 miles long) and their frequent renewal resulted in major disturbance to the grass heaths.

A number of lichen species are restricted within Britain to Breckland where they grow in botanically rich vegetation on chalky soil. Some species typical of this community are found at sites where chalk rubble has been produced by human disturbance, including the building of wartime banks to prevent gliders from landing, the stripping of topsoil for road building, the burial of equiment from mustard gas production and the creation of spoil heaps from flint mines. Flint mining was a major local industry in the Neolithic, and more recently in the past century, when flint knappers in Breckland supplied all the gunflints for the British army in the Napoleonic wars.

Although rabbits are relative newcomers, they now seem to be essential for preserving many habitats considered characteristic of Breckland. During a vegetation survey we found that acidic moss/lichen heath is now restricted to areas which are still, or were until very recently, heavily grazed by rabbits. It seems that rabbits are replacing the role of early farmers and flint miners in regularly disturbing the soil. In the absence of a mosaic of shifting cultivation and human disturbance, rabbits are exellent at providing a patchwork of bare sites near burrows and scrapes, closely grazed turf around the burrows and longer turf away from the burrows.

The importance of rabbits was shown in the mid-1950s when the disease myxomatosis was deliberately introduced into Britain. In Breckland, as elsewhere, it dramatically reduced the rabbit population and the heaths rapidly became overgrown. Rabbit populations recovered on a number of heaths and were at high levels in the 1970s. However, since then they have declined. The low rabbit numbers on many heaths result from a combination of cold, wet summers (which reduce the survival of young in the burrows), increased numbers of predators following the reduction in the number of gamekeepers, and the effective control of rabbit populations by agriculturalists who regard them as a serious pest. Thankfully, the hot summers of the past two years have helped to restore populations in some areas, but they are still at a critically low level on many valuable sites.

Part of the cause of the decline of this habitat may be the same as that of another famous East Anglian habitat – the Norfolk Broads. The Broads are clearly suffering from eutrophication – with large algal blooms due to nutriet enrichment – and work in the Netherlands suggest that the same process may damage heaths. The characteristic vegetation of heathlands partly depends on their infertility, so that even a small addition of nutrients may have a large effect. The conentration of nitrates in rain has doubled since the mid-19th century. Although Breckland has particularly low rainfall, the rain falling in this region contains the highest levels of nitrates in Britain. The Dutch studies have shown that increased inputs of nitrogen change the species composition of vegetation, with rank grasses becoming dominant. Our own evidence of a change in vegetation, and the documented loss of species of birds and plants that require open habitats, illustrate a similar change from sparse lichen heath to rank grassland.

Nutrients used to be removed from the breck and heaths in a number of ways. Crops such as rye were sometimes taken from the land. Bracken was cut for fuel, thatching and litter, and the right to mow the ‘breakes or fearnes’ was highly valued by commoners. Sheep which grazed on the heaths during the day were often folded on to arable land at night to enrich the field with their dung, thus depleting the heaths of nutrients. This practice is now used by Dutch conservationists to restore heathlands to their infertile state. By contrast, in Breckland in recent decades, supplementary feeding of stock grazing on the heaths has increased fertility on some sites leading to a decline in their conservation value.

The removal of rabbit carcasses during warrening represented a massive drain of nutrients from the site. In the late 18th century at one Breckland warren up to 40 rabbits per hectare were harvested each year. The soil and vegetation was so impoverished by centuries of warrening that by the 19th century rabbit populations yielded better harvests on the heaths and brecks outside the long established warrens.

It is likely that these explanations work together. Once rabbits have disappeared from a site due to myxomatosis, culling or bad weather, the growth of vegetation can then make the site unsuitable for them, hindering their return. Eutrophication ensures that the vegetation responds more quickly to their absence, and successional change of the vegetation then increases the fertility of the soil. Many heaths have now reached the point where they are unsuitable for rabbits. However, the management of heaths by sheep grazing or mechanical cutting has sometimes enouraged the regrowth of remaining rabbit populations.

The history of Breckland is an interesting part of our culture but it also indicates the management necessary to preserve the heaths. The consistent feature of Breckland is that it has always been disturbed by flint workers, farmers, rabbit warreners, the military and rabbits. This distrubance has often been accompanied by nutrient depletion and grazing. If we wish to maintain these unique habitats it is likely that we will have to mimic these unique aspects of their history. Disturbance is as much a traditional part of the management of Breckland as coppicing is for many ancient woods or haymaking is for hay meadows. It may be that nature reserves have been overprotected and need some sort of disruption to maintain open ground. The importance of disturbance is illustrated by the fact that many of the remaining sites for plant rarities are not on carefully protected reserves but on roadsides and industrial estates. One of the few remaining sites in Britain for smooth rupturewort is a manhole cover in a housing estate in Thetford.

In collaboration with the Norfolk Naturalists Trust and the Nature Conservancy Council, we are experimenting with stripping off topsoil, ploughing, forage harvesting and rotovating. These are various ways of setting back succession and reducing soil fertility. Ploughing or subsoiling may bring subsoil that is poor in nutrients to the surface, but the seed bank found in the top few centimetres of soil may become deeply buried, losing much of its value. Rotovating encourages germination from the seed bank and can reduce the fertility of the soil, as soluble nutrients become leached instead of being taken up by plant roots. We have studied plots that were regularly rotovated in the past decade and are still recognisable as blocks of sparse grass heath with a diverse range of annuals and lichens, surrounded by tussocky grassland containing few species.

Rotovating mimics the old practice of plough breasting where ploughs were drawn through areas of sandy heathland to clean the shears. A number of traditional sites for plough breasting supported populations of rare Breckland plants that have been lost since the practice was discontinued. Of course, such management may be unsuitable around archaeological sites of geological sites.

There is considerable room for optimism about the future of Breckland. As we learn about the consequences of different management regimes, we should be able to help to restore the remaining heaths. Breckland has been designated as an ‘environmentally sensitive area’ by the Ministry of Agriculture, Fisheries and Food. As a result grazing has been reintroduced to some heaths. However, the suggested management prescriptions may require refinement as we understand more about the dynamics of the grass heaths. We may even be able to reverse some of the massive losses in habitat; under MAFF’s environmentally sensitive area and set-aside schemes, farmers are being encouraged to allow areas of arable land to revert to grass heath. With a combination of research and political will it should be possible to restore Breckland to its former ecological glory.

The importance of history in ecology and conservation is often underestimated. It would be interesting to know the detailed history of fens, reedbeds, woods, commons and heaths. We have no doubt that it would improve our knowledge of how they should be managed.

Paul Dolman and William Sutherland are ecologists at the University of East Anglia.