Surrey's Habitats : Chalk Grassland

Chalk grassland supports a rich and diverse flora with many rare and scarce species. The associated fauna, particularly invertebrates, is equally diverse and includes many scarce butterfly species.

Chalk grassland is often associated with downland. This is because of the way downland was created leading to a nutrient-poor environment which allowed these species to thrive by exploiting a particular niche. The grass-covered chalk North Downs are part of the traditional image of Surrey in summer. The short springy grass characteristic of chalk grassland, also known as lowland calcareous grassland, grows over a thin layer of nutrient-poor soil on chalk or limestone hills. These hills keep the soil very dry because water either runs down them before it can be absorbed, or quickly drains through the chalk.

It may seem strange that such an unwelcoming environment would support so many species, but it is the very fact of its low fertility that stops more common and less specialised plants taking over. In terms of number of plants and associated insects, chalk grassland is one of the richest vegetation types found in the British Isles. In Surrey our chalk grassland is well known for its variety of orchids and grasses found nowhere else. In turn, these flowers and grasses support vibrant and busy populations of butterflies and other insects.

The habitat was created many centuries ago. It is thought that initially gaps were created in the tree-covered downs by the grazing of native species such as deer. Starting some 6000 years ago, these gaps were then subsequently cleared by man to build dwellings, provide fuel and give somewhere for domestic animals to graze. A combination of poor soil and grazing determined how these landscapes evolved in the past. The animals – usually cattle and sheep - ate the woody plants, which would otherwise have scrubbed up the land, and hence they prevented rotting plants from enriching the soil. Grazing by livestock has declined since the middle of the 19th century, and by the Second World War few areas were grazed. In more recent times, rabbits partially took over this grazing role, until their populations were reduced by myxomatosis in the 1950s.

Once grazing stops, scrub and then trees begin to grow and alter the habitat. The main effect is that they help to both retain nutrients and acidify the soil until it is no longer able to support the previous variety of plants. Another consequence is that the shrubs and trees overshadow the ground flora.

Only a century ago, grassland would have covered much of the chalk hills of England. However, the loss of active farming has led to massive reafforestation of the Downs and hence the loss of much of our downland. Today it has been estimated that around 324 hectares of chalk grassland remain in Surrey, making up 3% of the chalk grassland in South East England.

Reserves with this habitat

Newlands Corner & Silent Pool
Norbury Park
Betchworth Quarry & Lime Kilns
Brockham Limeworks
Colekitchen Down
Nore Hill Chalk Pinnacle
Dawcombe
Dollypers Hill
Fames Rough
Fraser Down
Hackhurst Downs
Howell Hill
Inholms Claypit
Manor Farm
Park Ham & Quarry Hangers
White Downs
West Humble Bat Reserve
St Martha's Hill
Shabden Park
Seale Chalk Pit
Wotton, Broadmoor & Abinger Commons