What is scrub?

Scrub provides valuable shelter for birds and insects but too much of it can be a bad thing, so Wildlife Trust staff and volunteers spend much of the winter removing it from our nature reserves.

Scrub comprises shrubs such as hawthorn, blackthorn, dogwood, gorse and bramble, together with young trees of prolific seed producers like birch and willow. Left untouched this scrub would rapidly spread.

Lowland heath, chalk grassland and many other valued habitats are 'plagioclimaxes' (a habitat where the influences of humans have prevented the ecosystem from developing further) where this succession has been halted by actions such as
grazing, cutting or burning.

How was scrub controlled in the past?

Open habitats of the past would have been maintained by grazing animals and local commoners living off the land, cutting birch, gorse and other woody vegetation for shelter, fuel and their livestock.

Many wild species came to rely on the open spaces created by this way of life and much of our work today replicates these actions for the benefit of wildlife.

Taking heathland as an example, too much scrub negatively impacts the specialist wildlife that thrives there – birds like woodlark or butterflies such as the silver-studded blue that rely on open habitat. If scrub was left unchecked then the heathland would be lost, replaced by silver birch woodland.

How do we control scrub today?

‘Scrub bashing’, as it is often called, is our typical method of scrub control, where volunteers armed with bowsaws and loppers cut down the scrub. If we don’t want it to grow back we will paint a dab of herbicide onto the stump to kill the roots.

Bonfires burn some of what is cut, other cut material is gathered into piles which are left to decompose, providing perfect habitat for invertebrates and reptiles.

It is common practice to leave a few patches of scrub and the occasional tree to grow on to improve diversity and structure. A good example of this is leaving lone trees on the heath for male nightjars to use as a perch in the breeding season. From their perch, they issue their rattling churr to attract females.

All scrub clearance is carried out between September and February so as to minimise disturbing wildlife, particularly nesting birds and reptiles. 

To clear scrub on a large scale there is always the option of chainsaws or brushcutters and tractor-mounted flails or mulchers. They do a speedy job but come at a greater cost and with an increased risk of disturbance.

Large machinery would not be appropriate on the small heathland reserve of Decoy Heath, where a population of rare adders exists. Here we deliberately leave areas of scrub for summer cover and hibernation below ground in winter. Large machinery could have dire consequences.

Gorse is an important component of the wide heathland expanse of Greenham and Crookham Commons but in places it dominates to the detriment of other wildlife, especially ground flora on the acid grassland.

For the past eight years BBOWT has carried out extensive cutting of gorse to reduce its extent. But there is a balance to be struck between opening up heathland and grassland for species such as woodlark and ensuring enough dense gorse cover for birds like Dartford warbler and stonechat.

Why has BBOWT been burning gorse?

Much of this gorse removal is achieved through mechanical cutting and mulching, but for the last couple of years we've trialled burning stands of gorse. The burning was focussed on tall over-mature gorse, which has less wildlife value.

Some of it will re-grow into thicker stands that support a great diversity of wildlife. Burning is far more cost-effective, though there are obvious risks associated with starting fires on a nature reserve!

To minimise the hazards, all burning is carried out by trained staff working with the local fire brigade. Burning like this does not contribute to climate change because as the gorse regrows it will absorb more carbon dioxide than is released during burning.

Scrub removal is an efficient way to maintain habitat but scrub will always grow back from roots or seeds so it isn’t long before we’re back out on the task.

By managing the level of scrub on our nature reserves BBOWT continues to ensure a diversity of habitat and structure for wildlife.

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