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Rooting For Nature - using pigs as a proxy for wild boar.

Stephen Jenkins


‘Rooting for Nature’ is a conservation project on an area of common land in West Wales, working with British Saddleback pigs to clear an area of extensive bracken, and regenerate the latent seedbank. This blog explains what the problem is, and why I have decided to use this method to solved that problem. It will hopefully provide a blueprint for landowners elsewhere to do something similar, where mechanical or chemical management of bracken is unfeasible, or ineffective. Utilising a natural process, this project looks to the past to present a more holistic method of bracken control for the future. It is an example of a rewilding action rather than a rewilding project - I.e., the rootling of pigs/boar to keep rhizome-based plants in check, and allow biodiversity to flourish.



The ‘Rooting for Nature’ project is taking place on the slopes of Carningli Mountain, part of the Preseli Hills Mountain range. Carningli towers gracefully over the coastal town of Newport, in Pembrokeshire, West Wales, and for many centuries has been Common land, owned by the Barony of Cemaes. The project has permission from the Carningli Graziers Association, the Barony of Cemaes, and every relevant statutory authority, to fence off approximately 20 acres of extensive bracken, for the period of twelve months, and employ British Saddleback Pigs to clear it. In doing so, they will till the earth, expose the latent seed bank to the light, and hopefully regenerate a more diverse habitat.


Unfortunately, in recent times, the grazing management of the Common has become very damaging to the habitat on the mountain. In years gone by, there would have been more mixed grazing, with heavier, native cattle and ponies grazing alongside sheep in a more harmonious way. Today, it is still technically a mixed grazing system, but the ecology of the mountain is being driven entirely by three large sheep flocks. There are a small number of cattle turned out in the summer months, and a small herd of ponies roams the mountain, but the sheep, alongside the intensive annual burning of the mountain, are what are causing the problems.

Carningli is in fact designated a SSSI for its ‘oceanic heathland vegetation’; a generous designation, as the heathland vegetation is in very poor condition. In fact, walking across the mountain you would do well to find any heather that is above ankle height. It may exist there on the ground, and will provide flowers, which glow purple in late summer, and give the impression that all is ok. However, almost all of this heather is in the first stage of its life cycle (the pioneering stage), where it has little value for nature, but the grasses and new shoots come through for the sheep. Heather has a life cycle of over thirty years, and it is most valuable in its mature stage, between the ages of 15-25 years, when it can provide cover for ground nesting birds etc. In its final ‘degenerating’ stage, the heather canopy opens up for new seeds to regenerate, thus a balance of different age structures could exist. In years gone by, Curlew bred on the mountain, but with the grazing and burning, very little mature heather habitat remains, and the Curlew vanished years ago.

When the mountain is burned, the sheep then nibble out the regenerating shoots, which are slow growing at any rate, and under browse on the gorse. This leads to an unbalanced ecosystem. Sheep are not native, and have not therefore coevolved with our own flora. Native cattle on the other hand, would leave the heather shoots alone, in favour of the faster growing gorse, thus allowing the heather time to grow. The cattle would then browse on this heather when it is mature, and it would in fact be a good source of winter forage, but it would exist within a balanced ecosystem, and provide habitat for other species.

One consequence of burning, followed by intensive sheep grazing then, is gorse dominated areas, unbroken by trees which might shade it out, and reduce its vigour. This creates a ‘fire load’, a justification for more burning. Another consequence is that, lower down the mountain (for now), extensive bracken forms, spreading into the newly open spaces, devoid of vegetation.

This extensive bracken marginalises the available pasture for the livestock, which then get concentrated more on the heathland vegetation higher up. This heathland vegetation is then, as mentioned, burned to convert it into pasture. However, where the heathland vegetation is burned, there is nothing to arrest the spread of the bracken. On the northern slopes of Carningli, you can see vast areas of this bracken, and immediately above it, bare earth that was burned within the last five years. Here, the bracken fronds are already starting to emerge. Above this, there is scorched earth from this year's burns, another area where the bracken will expand into.

Bracken is one of the oldest native plants in the UK, and as such, it has developed excellent means of expanding. It does so through underground stems, called rhizomes, which creep along, and store up energy. When enough energy is stored, new fronds emerge, covering new areas in monoculture. That is what is happening on Carningli. The constant cycle of burns and intensive sheep grazing is worsening the problem every year. The sheep will nibble out anything that might compete with, or shade out the bracken, and they leave the bracken alone due to its toxicity.

Bracken is not only toxic to the sheep, cattle and ponies on the mountain, but its spores are carcinogenic to people. A ten-minute walk, through bracken in the summer means inhaling thousands of these spores, not ideal on common, open access land, above one of the most popular tourist hotspots in the UK. Furthermore, the bracken creates a humid microclimate, perfect breeding ground for tics, which of course, carry disease, and are a huge problem for the graziers on the mountain.

This is not to say that bracken is without value. As part of a balanced ecosystem, bracken serves wildlife as much as any other plant. The microclimate it creates can lead to very rare plant communities developing under its canopy, but it is the vast, extensive nature of it on the mountain that is so problematic. It creates a monoculture, consuming more of the mountain every year, and reducing the complexity of the ecosystem.

Native cattle and ponies would improve the situation to some degree. Although they are also vulnerable to the toxicity of the bracken, their trampling effect would reduce the bracken somewhat. However, given the vast extent of the bracken on Carningli, it would take a very intensive number of livestock, over a very long period of time to start seeing any improvement. Cattle and Ponies would be much more adept at stopping the bracken from spreading, rather than clearing large amounts of it.

Enter the pigs... mewn gyda’r moch! The purpose of bringing in pigs for this task is that their wild ancestor, the wild boar has evolved to rootle around and eat bracken rhizomes, or the rhizomes of any plant, thus restricting monocultures and allowing the space for biodiversity to flourish. It is a niche that they have filled expertly, and they have a completely different impact on bracken to horses or cattle. They are highly tolerant of the toxins in bracken, and even though in this project they will be consuming high amounts, correct supplementation means there are no ill effects at all.

The British Saddleback pigs used in this project will simply act as ecological proxies for the wild boar. As mentioned, the rhizomes by which bracken spread are full of energy, which is why the industrious boar was so keen to get to them! It is for this same reason that pigs are so adept at clearing the rhizomes, that other methods are so much less effective. Whereas pigs target the rhizomes for their calorific content, this stored energy makes cutting, bruising or trampling the bracken a tiresome endeavour. When bracken is treated in this way, the energy stored in the rhizomes means the bracken comes straight back, and the treatment must work at a rate where energy is being drawn out of the rhizomes faster than it is being stored through photosynthesis. When the bracken is so vast and invasive, there is a lot of potential to store energy. Pigs literally tackle the root of the problem (although rhizomes are stems, not roots, so perhaps not literally!)

When we envisage pigs in the landscape, we invariably associate them with agriculture. Pigs that are lucky enough to spend some time outside, are generally kept in a small field, and there is no rotation. The pigs then over plough the soil, causing damage, which is a common accusation levelled at pigs. When I mention my project to people, the genral response is “oh yes, pigs will get rid of everything”, but this rather misses the point that pigs, as proxies of the wild boar, have evolved to target these rhizomes, and in a natural setting, would keep ecosystems in a perfect balance.


This project will closely monitor the pigs, and move them on to a new area as soon as the bracken rhizomes are cleared. This will stop them from over working the soil, and eating anything undesirable, such as bulbs, which they are also fond of! I will also be monitoring the project in other ways. The two concerns of Welsh Government with this project were the impact of the pigs on soil compaction, and soil enrichment. I will, therefore, be taking a chemical profile of the soils before and after the project, as well as using a penetrometer to compare soil compaction. If the project is successful, and the method is used elsewhere, we can then advise on perhaps lowering the stocking density, if there is too much of an impact.

I will also be monitoring the adjacent river Ceunant, for any effects of diffuse pollution. Natural Resources Wales installed a sonde measuring device in the river prior to the pigs moving in, and will do so again once the pigs have left, comparing the results.

Finally, I will be measuring the extent to which the bracken has been removed. This will be done with many, many photographs, and some drone footage. I will also be measuring the rhizomes biomass by digging out 50cm x 50cm rhizomes pits, and weighing the rhizomes.

In rooting around for the rhizomes, and tilling the earth, the pigs will then expose any latent seed bank to the light. Vegetation that has been unable to grow due to the dense bracken canopy, and bracken litter, will have room to grow again. The project area changes significantly in terms of soil profile and altitude, so the vegetation that could potentially return would be a mix of heathland and acidic wood pasture. There are areas of wet heath, valley mire, wet flushes within or nearby the project area, that will be fenced off from the pigs, and so the long-term habitat could be a fantastic mosaic.

However, the returning vegetation will depend entirely on the grazing system that is in place, which is why this project is part of a wider ambition to manage the whole of Carningli common in a much more nature friendly way. I will write more about the plans for when the pigs leave in a separate blog post. For now, I hope this gave a good enough overview of the purpose of the project, and I look forward to updating on its progress in the future.






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