Aghatirourke RSPB reserve, Cuilcagh Mtn, Co, Fermanagh, September 2002

Scrub on chalk and limestone grassland

Scrub on chalk and limestone grassland is an integral part of the landscape and can be managed without compromising other important wildlife, landscape or archaeological features.

The benefits of chalk and limestone soils for wildlife

Scrub on chalk and limestone soils generally contains a diverse range of shrubs.

This maximises the flowering and fruiting period, ensuring a rich source of food and shelter for wildlife.

When well managed, it is thinly spread across open grassland, generally covering up to 5% of an area. When it includes a variety of ages, structures and plenty of edge, it increases biodiversity on grassland.

A varied range of species, age, structure and distribution of shrubs is important because it provides different habitats. Tall herbs require sheltered scrub edge. Insects benefit from a diversity of age, leafing and flowering periods. Birds like structures ranging from young scattered bushes to mature scrub with a dense canopy.

Natural colonisation of scrub

Scrub naturally colonises new areas. As long as the balance with open grassland is retained, this is beneficial.

  • Allow scrub to colonise where there are no threats to archaeological or landscape features. To offset this and maintain the desired balance, remove some older stands.
  • Where it is not possible to ‘move’ scrub in this way, use browsing and/or rotational cutting to maintain stands.

Juniper

Juniper is becoming rare. Where it survives, it is usually as old, single-aged stands.

Regeneration from seed is vital to ensure the survival of the stand and diversify its age and structure.

  • Juniper seeds require open, disturbed ground in which to germinate. Such areas adjacent to existing juniper offer ideal conditions.
  • It is vital to protect seedlings from browsing by rabbits, deer and livestock.
  • Selective management is needed to maintain healthy juniper bushes. Juniper is slow-growing and can suffer from crowding and shading by other shrubs.
  • Over-grazing is the main cause of poor regeneration. Fence stock into small enclosures for short bursts of light grazing to create the open sward conditions that are ideal for seedling establishment. Monitor the effects and move the enclosures and stock to the next target area as required.
  • Where juniper occurs, seek specialist advice.    
Haweswater RSPB reserve. Juniper (Juniperus communis) woodland on the hillside above the reservoir - an increasingly rare habitat. Cumbria

Why manage scrub on chalk and limestone grassland?

Scrub is an important component of chalk and limestone grassland. However, it needs management to maintain it in good condition for wildlife, and to ensure it does not spread into areas where it is not wanted.

Long-established scrub enriches the soil and, if removed, thick grasses will grow. It would take many years for the area to return to flower-rich grassland. Scrub should be controlled in areas of archaeological, landscape and wildlife importance.

Management techniques

Scrub is a dynamic habitat that benefits from rotational management. Encouraging scrub to ‘move’ around a site will retain age and structural diversity and benefit species requiring the pioneer stages of scrub development.

  • Cutting can be used to maintain or restore scrub stands or clear unwanted scrub.
  • Cut between early September and the end of February to avoid the bird breeding season. Cutting at the end of winter allows birds and mammals time to eat any berries.
  • Carefully select areas for access and as burn sites, avoiding important areas for wildlife or archaeology.  
Limestone pavement. Orton Fells. Cumbria, England

Maintaining and restoring scrub

  • Grazing is an important management technique. Cattle and ponies can break up blocks of scrub by trampling and browsing. Goats can strip bark and, if used carefully, will produce structural diversity. Some breeds of sheep are good at browsing and pushing through scrub, but younger animals and lighter breeds are prone to getting caught up in it. Start with a low stocking rate for the species and breed (around 0.25 LU per 0.01 sq km), monitor the effects and adjust accordingly.
  • Where practical, diversify large, evenly aged scrub patches. Cut a section at a time – for example, 1/15th each year or 1/5th every third year.
  • Cut adjacent sections of scrub in sequence, to benefit wildlife with poor dispersal abilities. This helps by providing successive areas of the species’ favoured habitat (see diagram below).
  • Selective thinning of bushes ensures structure is maintained for mosses, lichens and fungi that require continuity of age, shade and humidity.       
 Sheep grazing at Winterbourne Downs RSPB reserve (Manor Farm). Wiltshire, England.

Removing scrub

  • On accessible slopes, old or unwanted scrub can be removed quickly and efficiently with a digger. This removes the scrub, its roots and nutrient-rich top-soil to re-expose the mineral soil and restart natural succession.
  • Do not use a digger where it is likely to damage wildlife or archaeological sites. In these situations, scrub will need to be cut.
  • The stumps of most species will regenerate. They can be treated with herbicide – either by treating individual stumps or weed-wiping regrowth – followed by browsing from livestock.
  • Stumps are important for wildlife, especially fungi and insects. They should be left, except where access or maintenance, such as mowing, is required. Removing stumps from archaeological sites is likely to cause damage.           

Difficult-to-manage species

Some species – in particular, blackthorn, dogwood and privet – are difficult to remove and will spread vigorously in response to cutting.

  • Where necessary, and there are no limiting factors (such as access, archaeology, landscape or wildlife), grub out using a digger.
  • Where this is not possible, cut the scrub and weed-wipe regrowth with herbicides.
  • Goats can usually control regeneration within two or three seasons.
Waxwing Bombycilla garrulus, adult feeding in hedge of Wild privet Ligustrum vulgare, Bedfordshire, England

Preventing scrub establishment

On sensitive areas and for certain species, it is important to prevent the establishment of scrub.

This applies to native and, particularly, to introduced species. Two species of concern are the butterfly bush (Buddleia) and cotoneaster, which are often introduced via bird and animal droppings or coats.

  • Grazing will suppress scrub establishment. The stocking rate needed to maintain the grassland is usually sufficient (around 0.25 LU per 0.01 sq km), but may need to be increased to tackle a particular problem.
  • Mow in conjunction with grazing or where grazing is not possible. The best time to do this depends on the wildlife present. Insect eggs and larvae are often the most vulnerable. Avoid mowing until late summer/autumn to allow time for flower and grass seeds to drop, or late winter/early spring to give overwinter shelter for insects. Where possible, cut a portion of the area in each period and alternate this annually.
  • Where plants have begun to colonise, remove seedlings immediately, as heavy infestations are harder to eradicate. Hand-weed or use a garden fork to avoid leaving roots.
  • Check for new plants the following spring, and hand-weed or lift as appropriate.
Painted lady Vanessa Carduip, feeding on buddleia