Why the spread of bracken spells danger

Alarm bells are sounding across Yorkshire’s uplands as bracken control comes under the cosh. Ian Rotherham reports.

Bracken is a part of the open country landscape, on upland moors or the now, all too rare, lowland heath and common. Golden-brown colours of autumn and winter, and fresh green swathes of summer are truly delightful.

Yet although a true native and not an alien invader, bracken fern has spread rampantly across many moors and heaths, threatening wildlife, land management, and even human health.

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The long-term cause is a phenomenon called cultural severance through which traditional management and nature are separated from local communities and the economy.

In short, we made use of bracken in farming and now we don’t. No longer cut, harvested, and used, the fern has spread insidiously across the landscape.

Traditional upland cattle grazing helped to keep it under control, whereas sheep grazing does not. Some conservation management occurs by cutting and heavy rolling as used to be done by farmers. But in truth, this only skims the surface of a big problem.

The only effective weapon in the farm or conservation toolkit is a chemical spray called Asulam or Asulox.

Its use is being challenged by EU regulations – there has been a reprieve but only temporarily.

It was with this in mind that Yorkshire-based world bracken expert Dr Roderick Robinson, contacted me to raise the issue.

“This is the only selective, effective and safe herbicide able to kill bracken, while not harming heather, bilberry, grasses and other flowers,” he said.

“Bracken is invasive, persistent and a national problem on permanent grazing. It needs management by Asulam in uncultivated areas to contain its spread and to convert back into better habitats some of its substantial area of dominance (263,000 hectares according to the 2007 Countryside Survey).

“Even this is an under-estimate. Restoration provides more biodiversity and economic benefits for farming.”

Termination of Asulox registration would mean the loss of aerial application and the end of all significant bracken control.

The experience of most heather moorland managers is that uncontrolled bracken will increase and dominate.

In this way, we lost 40 per cent of heather between 1945 and 1985, and we need to reverse this.

Preventing the further spread of bracken and reclaiming vegetation back to heather vegetation, is the way forward.

Loss of control would cause declines in wildlife habitats, like permanent pastures, heathland, moorland, and other conservation sites, including SSSIs.

Rare fritillary butterflies and moths would be threatened, along with chough, moorland birds like curlew, Dartford warbler, rare lizards and snakes, with widespread loss of flora and dependent biodiversity through bracken dominance.

The area of bracken would double in 35 years, with a two per cent annual increase in area, to 14 per cent of UK land surface.

Associated cancer incidence would increase via drinking water and milk, and louping ill (a viral disease mainly of sheep), Lyme disease, tick pyaemia, red-water fever and others, would increase because of sheep ticks.

There would be widespread socio-economic effects and problems for shepherding, animal health and overgrazing.

Bracken spread reduces sheep and beef production, thereby increasing food prices and imports, and, in turn, affecting transport, fuel, and CO2 emissions.

Bracken rhizomes may damage archaeology on heather moorland where conditions are otherwise ideal for long-term preservation. From July through to November, bracken also makes the gathering of sheep very difficult, with welfare implications and reduction of available grazing land.

Roderick Robinson concedes that bracken is native and does have some environmental benefits but these are hugely outweighed by the disadvantages.

“We do not want annihilation – just control and management,” he says.

Fertile bracken produces carcinogenic spores in August and September and anyone working in bracken beds should wear facemasks during this period.

There may, of course, be issues for walkers and outdoor sports enthusiasts since most affected land is public Open Access with many miles of public rights of way.

I asked Roderick why Asulam is important in bracken control. The simple answer is that other herbicides can be used, but they kill all green vegetation. Asulam is the only selective one.

There are other methods, like ploughing to 20 centimetres depth, but this is unthinkable on uncultivated landscapes, and most heather moorlands are areas such as Sites of Special Scientific Interest.

Other approaches are impractical in uncultivated landscapes, so Asulam is the only product that controls bracken but does not damage other vegetation.

This last point is important, as it is essential to get plant cover established to prevent soil erosion.

Asulam is trusted by the industry, has been widely used since 1960, and is one of the few chemicals still cleared for aerial application.

Bracken clearance is long-term with annual treatments for up to a decade. To break that programme for even two or three seasons could be disastrous and waste the money spent up to that point.

Ultimately, the process would need to start again involving even more chemical application and more cost.

Between 1990 and 2007, government departments such as Defra funded substantial programmes for bracken management with Asulox and these are ongoing in many Higher Level Stewardship (land management grant aid) schemes.

If the use of Asulox is withdrawn, much public money and private investment will have been wasted, and environmental damage will ensue.

A complication is the link between aerial application and bracken control with Asulam, which Roderick says are interdependent.

Control of bracken forms 95-100 per cent of all aerial control work and is 90 per cent of the UK market for the product, so the loss of one means the loss of the other.

A blocking minority by six EU Member States prompted the turnaround in mid-March, but the European Commission is still pushing for a ban in the longer term.

The National Farmers’ Union Scotland had appealed to almost anyone in Brussels with a rural and environmental interest for support in lobbying for a reprieve.

Ultimately, the move to maintain Asulam use was supported by Scottish Natural Heritage, SEPA, the Scottish Government, Defra, Natural England, the Environment Agency, NFU England, and by MEPs.

Now, farmers and land managers are lobbying for Asulam retention for control of bracken and dock. Removing it from the market would be a real blow and the implications for North Yorkshire and the Pennines would be serious for both conservation and the economy.

Ian Rotherham is Professor of Environmental Geography, Reader in Tourism and Environmental Change and co-author of Bracken and its Management published by STRI.

Bracken’s threat to health

Bracken is ideal habitat for ticks which spread many diseases in sheep, grouse and wild birds.

Parts of the bracken plant are toxic – causing organ failure if eaten by farm animals – and contain cancer-inducing chemicals spread by air, water and by eating.

The toxin Ptaguilaside is water-soluble and ends up in drinking water. Our supplies often come from moorland areas and where bracken is abundant in areas of upland water catchment, carcinogens have been measured in water at levels as high as 45 micrograms per litre – the acceptable maximum is 0.005 to 0.016.