Why heathland needs managing at all

Heathland looks wild, but almost every acre of it has been shaped by people. Centuries of grazing, cutting and burning kept birch, pine and bracken at bay and allowed heather, gorse and fine grasses to flourish. When that management stopped in the twentieth century, scrub moved in fast. Lowland heath in England now covers roughly a fifth of what it did in 1800, and the species that depend on it — nightjar, Dartford warbler, woodlark, sand lizard, smooth snake and the silver-studded blue butterfly — have suffered accordingly. Keeping heath open is not neglect; it is deliberate, repeated work.

Birch and pine: the relentless colonisers

Downy birch is the classic invader. A single tree can release a million lightweight seeds that travel on the wind, and seedlings will establish in almost any gap. Left alone, a heath can move from open heather to dense birch woodland in fifteen to twenty years. Scots pine behaves similarly on dry, sandy heaths, and both cast the shade that heather cannot tolerate.

Managers use a ladder of techniques depending on the size of the problem:

• Hand pulling for seedlings and saplings up to about a metre, done when the ground is damp so roots come away cleanly.
• Brushcutters and clearing saws for thicker stands, cutting at ground level and often followed by a second visit the next season.
• Chainsaws and cut-stump treatment for mature trees, where a herbicide is applied immediately to the cut surface to prevent coppicing.
• Stem injection or plug treatment where felling would disturb sensitive ground or archaeology.

The catch is the seed bank. Birch seed remains viable in the soil for years, so one pass is never enough. Most sites need follow-up for at least three to five seasons before the pressure eases.

Bracken: the underground threat

Bracken is different. It spreads not mainly by spore but by an underground network of rhizomes, some reaching a metre deep and many metres long. Cutting the fronds is therefore not killing the plant outright — it is starving it. The trick is timing and repetition.

• First cut in late June or early July, when fronds are fully unfurled and the rhizome is drawing on stored energy.
• Second cut six to eight weeks later, which prevents the plant from rebuilding reserves before winter.
• Crushing or rolling with a heavy roller, done at the point when stems are most brittle, which bruises the vascular tissue and sets growth back.

Done consistently for three to five years, cutting can halve bracken cover and allow heather and grasses to return. It also removes the deep litter layer that smothers everything beneath it. Timing has to respect ground-nesting birds, though, which is why many sites cut in late summer rather than earlier.

Grazing: the patient, natural tool

Nothing beats a hungry animal for keeping a heath open. Conservation grazing with hardy breeds — Exmoor and Dartmoor ponies, native cattle such as Belted Galloway, and Hebridean or Manx Loaghtan sheep — browses birch seedlings, tramples bracken litter and opens up tussocky grass. Ponies are particularly useful because they graze coarse grasses hard and will strip bark from young trees.

Getting it right is a balancing act. Too many animals and the heather is grazed to the bone; too few and birch wins. Most managers aim for a mosaic: short, grazed patches alongside taller heather for nesting and cover. Fencing, water supplies and welfare checks all have to be planned, and livestock need to be off wet areas in winter to avoid poaching.

Cutting, mowing and controlled burning

Mechanical mowing with tractor-mounted flails is the workhorse of larger sites, knocking back dense bracken and young scrub in a single pass. Controlled burning, known in parts of England as swaling, is used on a rotation of roughly ten to twenty years on suitable dry heath. Fires are lit in small strips under strict conditions, with trained crews, permits and a following wind, usually between October and March.

Burning removes litter, exposes bare ground where heather seed can germinate, and creates the age structure that reptiles and invertebrates need. It is not suitable everywhere — deep peat, sensitive archaeology and steep slopes are all ruled out — and it must never be a substitute for grazing or cutting.

Putting wildlife first

Every technique has a season when it must stop. Ground-nesting birds such as nightjar, woodlark and Dartford warbler are vulnerable from March to August, so scrub clearance and mowing are usually scheduled for autumn and winter. Reptiles need sunny, bare patches and tussocky edges left intact, and invertebrates rely on flowering heather and gorse stands that are not cut too uniformly.

Good managers also keep records. Fixed-point photographs, butterfly transects and bird surveys show whether the work is achieving what was intended, or whether scrub is quietly returning behind the cleared ground. Heathland is never finished. It is a habitat that has to be worked, season after season, if the open, buzzing, purpling landscape is to survive for the wildlife and the walkers who love it.