Carn Brea protection Group

Bracken and Carn Brea

When the Carn Brea Protection Group was formed in 1996, one component of the management proposals which the CBPG objected to was control of bracken by spraying with the chemical Asulox and enclosed grazing.

 Why does the bracken need controlling?

Well, as far as the CBPG is concerned, it only needs minimal control in very selective areas.

But Kerrier's view in 1996 was somewhat different, involving a 10 year rotational spraying program over several acres. They wanted to control the bracken for two reasons:

1 - Bracken is hazardous to humans.

2 - The bracken is taking over the Carn to the detriment of other native species of flora.

 Is bracken hazardous to humans?

Well, the short answer is 'potentially yes', but it is not quite that simple. Bracken spores have been shown to have potentially carcinogenic properties if inhaled in unusually large quantities. These spores are only released for a few weeks each year during July and August. The rest of the plant presents no health threat unless taken internally. The Devon Wildlife Trust only takes precautions for summer workers in dense bracken areas, and only if they are working in them "...all day, every day. This would apply only to staff who are actually working within the stand of bracken, not those just nearby. ...we do not consider bracken to be a great risk to public health. One would have to inhale an unusually large quantity of bracken spores before any risk presented itself - the sort of quantity only encountered by the prolonged daily exposure mentioned above."

It is easy to over-react to words like 'carcinogenic' without a full appraisal of the level of risk.

 Is bracken 'taking over' the Carn?

No. Traditionally bracken was harvested on the Carn during the Ferny Harvest, when it was used as bedding for animals. Photographic evidence shows that the Carn has had a significant covering of bracken since at least the 1800s and each season the bracken waxes and wanes in various areas of the Carn. In 1871 Charles Thomas, (Mining Fields of the West) refers to "Carn Brea ..... covered by a luxuriant growth of ferns (bracken)."

 Chemical Control of Bracken by Spraying.

The original plan to spray the bracken with chemicals was vehemently opposed by the local people in 1996. The chemical proposed was Asulox, which enquiries by the group was found to be nothing like as safe for people or other plants native to the Carn, as was being claimed. There are plenty of environmentally friendly alternatives available for controlling bracken.

 Grazing, ticks and Lyme Disease.

One of the hazards of bracken mentioned in the original proposals was the fact that ticks carrying Lyme Disease have been known to occur on bracken. Lyme Disease, which can prove fatal, was first discovered in Britain in 1975 and is prevalent in areas where there is tall vegetation and heavy grazing by livestock such as Dartmoor, Exmoor and the New Forest. Kerrier originally proposed grazing as another alternative for controlling the bracken. Ironically Lyme Disease and the ticks which carry it have NOT been recorded on the Carn, and whilst the area remains ungrazed this situation is likely to remain. Any proposal to introduce grazing on the Carn could conceivably introduce Lyme Disease to the Carn. Within the limits of the Carn, unlike Exmoor/Dartmoor, erosion from the trampling of ponies would be concentrated into smaller areas. Particularly vulnerable in SW prevailing winds are the more sheltered parts near the castle and monument, which are archaeologically sensitive. Other problems with grazing include fires, straying, theft, feeding, water, hazards to the public and the rough and stony nature of the Carn.

 Traditional and Non-Chemical Controls.

If it is absolutely necessary to control the bracken, then there are effective, non-toxic, well-tried alternatives; namely cutting and burning. Cutting was found to be better than chemical sprays by a ten year study conducted by the Institute of Terrestrial Ecology, who compared them for bracken control on heathland, and concluded 'cutting twice-yearly was the most effective treatment'. Burning is also worthy of recommendation as it is the traditional management tool for heathland and has long been practised throughout Britain. Indeed, many heathlands owe their existence to burning. On the Isles of Scilly they have come up with another method, bruising the stems (see photo below). They have found that breaking the stems causes the roots to continue trying to feed the stem, rather than spreading out new shoots, which happens if you cut the stems. Over a few years this exhausts the plant and it dies. This could very simply be achieved on the Carn by use of volunteers with sticks. It has been proposed in the past that a good use of people doing Community Service would be to manually clear areas of bracken (and knotweed) on the Carn.

The machine below is manufactured by Landbase - 'Equipment for Natural Management' Tel/Fax 01395 567880/443826.