Discover Chalk Grassland in the Chilterns Countryside
It is sometimes said that chalk grassland is Europe’s tropical rainforest, but unlike the rainforests, it is not entirely natural, having evolved over thousands of years under the grazing pressures of domestic livestock, especially sheep. However, like rainforests, chalk grassland it is home to a surprisingly rich and diverse range of plant and animal life.
Up to forty species of flowering plants can be found in one square metre of chalk grassland, and many species are unique to the habitat, including many beautiful orchids, gentians, wild candytuft and other wildflowers. In turn, the variety of wildflowers attracts many species of insect, including rare butterflies such as the Adonis Blue and the Duke of Burgundy.
When did chalk grassland form?
It is widely thought that the British chalk grasslands first appeared in the Chiltern Hills towards the end of the late Stone Age (Neolithic) more than 6 000 years ago, when farming slowly spread across these islands, replacing the way of life of hunter-gatherer communities. However, evidence from the analysis of fossil pollen shows that at least some pockets of chalk grassland may have appeared naturally on the steepest slopes of the chalklands at the end of the Ice Age, around 11 700 years ago.
Nevertheless, it was the clearance of woodland to create farmland towards the end of the Neolithic era that created the ideal conditions for the widespread establishment of chalk grasslands in Southern England. The thin rendzina soils that develop on steep chalk slopes are usually shallow and stony, and they don’t hold water for long. This combined with the steep gradients made the land unsuitable for arable farming, but it was useful for low-intensity livestock grazing, which in turn created the conditions for the formation of chalk grassland. So for many centuries, the species-rich chalk grassland has been maintained coincidentally as part of traditional agricultural practices, such as sheep grazing and hay-cutting.
The importance of grazing animals
Whether they are sheep, cattle, horses or rabbits, grazing animals perform a number of important roles in maintaining the chalk grassland ecosystem. By far the most important of these roles is nibbling off the young shoots of sapling shrubs and tree species, preventing them from growing into large bushes and trees. Without these larger plants, the grasses and the other flowering plants in the herb layer have access to sunlight and to the limited amounts of nutrients and water available from the soil. So the presence of grazing animals arrests natural succession towards scrub and woodland.The larger grazers also disturb the soil surface, providing oppotunities for a seeds to set, leading to a rich floral biodiversity.This, in turn, attracts a wide variety of insects, small mammals and birds that make up a complex food web.
The loss of chalk grassland
Chalk grassland has dominated the chalk hills of Southern England for many centuries, and it was widespread until the 1940s, covering many of the steeper slopes in the Chilterns, the North and South Downs, Salisbury Plain and the Lincolnshire and Yorkshire Wolds.
Since the Second World War, Britain has lost more than 80% of our chalk grassland. This is largely a consequence of changes in land use away from traditional low-intensity animal grazing and hay cutting. Intensive farming with the use of machinery, herbicides and artificial fertilisers has changed the nature of the soil and how it is used, so that the traditional chalk grassland in many places has been replaced by arable land or acres of grass monoculture with very low species diversity.
Grazing rabbits have contributed to the maintenance of chalk grasslands since their introduction to the British countryside in the Middle Ages. In the 1950s, the arrival of myxomatosis, a viral disease of rabbits, decimated the rabbit population, leading to considerably reduced grazing pressures. As a result, some areas of chalk grassland, once grazed by rabbits, became choked by scrub and tree growth. However, it is worth bearing in mind that uncontrolled rabbit populations can also to contribute to over-grazing, which can also prevent chalk grassland plants from flowering and seeding. In a well-balanced chalk grassland ecosystem, foxes, weasels, stoats, badgers, buzzards and even red kites help to keep rabbit numbers under control.
Other pressures on chalk grassland include road and building developments, chalk quarries and the demand for land for recreational purposes.
Low nutrient levels are good
The thin rendzina soils are lime-rich, but low in other nutrients. They hold little water and they warm up and dry out quickly in the summer sunshine. These stressed conditions prevent nutrient-hungry species of grasses from dominating the pasture, which is good news of the rare or unusual species of flowering plants that would otherwise be unable to compete with the grasses. So low soil nutrient levels are essential for allowing a more diverse range of flowering plants to flourish in chalk grasslands.
What plants should I look for?
Chalk grassland supports a wide variety of rare and unusual plants and animals, many of which have unique associations with this habitat and cannot thrive, or survive, elsewhere.
Grass species include quaking grass, sheep’s fescue, meadow-oat grass, crested hair grass, tor-grass, and upright brome.
Wildflower species include bird’s-foot trefoil, candytuft, clustered bellflower, common rock-rose, cowslip, dropwort, eyebright, field scabious, gentians, knapweed, hairy violet, harebell, hoary plantain, horseshoe vetch, kidney vetch, lady’s bedstraw, marjoram, milkwort, mouse-ear hawkweed, many types of orchid, ox-eye daisy, rest harrow, hawkbit, salad burnet, small scabious, wild basil, wild thyme, yellow-wort and many more.
Other species associated with chalk include wild juniper, found at Coombe Hill, Pulpit Hill and Watlington Hill, and numerous species of lichens and mosses.
What insects should I look for?
Many species of ant, ground beetle, bee and bumblebee can be found in chalk grassland. Rarer insects include the phantom hoverfly and wart-biter bush cricket. Yellow meadow ants are responsible for building distinctive dome-shaped anthills on chalk grassland.
You may see rare or unusual butterflies, such as the silver spotted skipper, Duke of Burgundy, chalkhill blue and Adonis blue. Rare moths such as the gothic moth and four-spotted moth can also be found on chalk grassland.
How does the National Trust manage chalk grassland?
The fragmentation of many areas of grassland has resulted in populations of a number of species becoming isolated and prone to local extinctions. The National Trust rangers and volunteers manage the pasture, in association with local farmers and other conservation groups such as the Berks, Bucks & Oxon Wildlife Trust, Natural England, and Butterfly Conservation, to link up chalk grassland sites with ‘wildlife corridors’, which allow species to spread and intermingle.
Where possible, the Trust uses low-intensity sheep and cattle grazing to maintain the grassland. Sometimes livestock will be removed in spring when the plants start re-growing and they stay off the pasture until the plants have flowered and set seed. At some of our sites, such as West Wycombe Hill, it is impractical to introduce grazing animals, so their actions are replaced by seasonal grass-cutting and careful mechanical or manual removal of scrub and tree saplings by our National Trust rangers, volunteers and contractors.
Our aim is to create a mosaic of different habitats within the chalk grassland. For example, some scrub areas, tussocks of long grass, areas of short-sward grass and even some patches of bare soil. This way, many species of plants fungi, insects, mammals and birds are supported.
What can you do to help?
- Join the National Trust to support our work on chalk grasslands and other threatened habitats.
- Volunteer with your local National Trust ranger team.
- Support local wildlife-friendly farms.
- Tell others about the importance of our special chalk grassland habitats. Why not share this page with your friends?