Category: #Rewilding

In a recent post, I described the Ragwort (Senecio jacobaea), as one of the plants most toxic to horses. In this post, I look at a related issue, concerning Ragwort and Rewilding.

Description:

Ragwort (Senecio jacobaea) is a biennial plant, abundant in Britain. It can grow from 30cm to a meter in height. Ragwort has bright yellow flowers, and the rough lobed leaves which give it its name. This plant was classed as injurious under the Weeds Act, 1959. Landowners may be subject to prosecution if they leave Ragwort on their land.

But Ragwort possesses benefits too!

The dangers of Ragwort are well-known. Especially to livestock owners, and equestrians. Yet Ragwort has many benific properties. What is less widely known is that Ragwort supports a thriving community of insects. Seven species of Beetle. Twelve species of flies. One Macro moth, the cinnabar moth. Seven micro moths. It is a source of nectar for 30 species of solitary bees. Eighteen species of solitary wasps. And fifty different species of insect parasites. According to Isabella Tree (Wilding), 177 different species of insect feed on Ragwort.

Isabella Tree devotes her entire chapter Eight (Wilding) to the subject of Ragwort. The problem is of size. One issue she discusses concerns the BEVA report of 2002. BEVA is the British Equine Veterinary Association. They reported that 6,500 horses died in 2002 due to Ragwort. Yet only 12 years before, data showed that only 10 horses succumb to the plant per year. This previous data came from the Ministry of Agriculture, Fisheries and Food. As such there was a huge discrepancy between the two reports. Isabella Tree has argued that the BEVA report used data from only 4% of BEVA members. They claimed on average three cases each of Ragwort poisoning. This figure was then extrapolated to the entire membership. It is clear there is a need for reliable data.

The reason I explore this in detail is that Ragwort inflames passions. And the plant – despite toxicity – has considerable benefits for a large number of insects.

Rewilding Britain and Ragwort

Rewilding Britain has also published a report on this plant. As they point out: ” The species is an important source of nectar and pollen. It’s a food plant for many insect species, including the cinnabar moth. However, ragwort is deemed to be toxic to livestock when taken in high doses. Animals will naturally avoid ragwort when grazing unless pasture is overgrazed and there’s a lack of food, but they can’t detect ragwort that’s present in hay. A large amount of ragwort — estimated to be around 5 – 25% of total body weight for horses and cattle — has to be ingested for it to be poisonous”. 

In terms of control, they suggest that action may need the use of herbicides. These are generally damaging to the environment. Cutting and removing the plants is labour intensive and expensive but is kinder to the land. In rewilding projects, patience is essential. It takes time to allow natural succession. With time, different species will replace Ragwort.

In the case of the Knepp estate, they maintain a topped 50m boundary. This prevents any possibility of Ragwort seeding neighboring land.

Wicken Fen National Nature reserve has tried a variety of methods. Ground cover is established to minimize the spread of Ragwort. This includes natural regeneration, seeding and hay spreading. Results have been mixed. No single measure prevented Ragwort seed from drifting onto neighboring land.

Seeding and seed dispersal

Studies have been carried out on seed dispersal in Ragwort. Seed carried by the wind tends to be lighter and also infertile. For a plant making 30,000 seeds, 60% will fall at the base of the plant. 39% will fall within 4.5m (15ft), and at 36m (120 ft), less than 0.005% of the seed can be detected. That is, less than 2 grains of 30,000. This study confirms that wind-borne seed transport is highly limited in Ragwort.

Conclusion:

In the end, I believe the best stance is truly difficult to determine. On the one hand, these plants are clearly toxic. On the other, they provide sustenance for at least 177 species of insect. To eradicate by hand (and I have done this myself, to protect horses), is one approach. At the same time, I am acutely aware of the insect habitats I have personally destroyed.

Can one maintain a 50m topped boundary? Wind studies show that seeds tend to disperse in a small area, local to each plant. If a boundary is not possible, eradication may be the better solution for neighbors.

This may be critical if hay or haylage is cropped close by your land. One of the most common causes of equine poisoning is dried Ragwort contaminating hay. Horses generally steer well clear of this plant. Its odor is unpleasant to them. But it can escape their attention if dried and baled with the hay. It is essential is to check one’s hay carefully. And if hay is produced on land bordering your own, I would control Ragwort very closely.

This subject is extremely complex. The discussion by Nogués-Bravo et al. (2016) makes this patently clear. Each situation must be studied on its own merits. I hope, however, that this reflection serves to remind that Ragwort has many benefits in the ecosystem. And that we need to find a balance between the needs of herbivores on the one hand. And the hundreds of insect species that this plant supports, on the other.

References:

Isabella Tree:
Wilding: The return to nature of a British Farm. Picador. 2018

Rewilding Britain:
Quick Guide to Ragwort:
https://www.rewildingbritain.org.uk/start-rewilding/quick-guide-ragwort-and-dealing-with-the-challenges

Rewilding is the new Pandora’s box in conservation
David Nogués-Bravo, Daniel Simberloff, Carsten Rahbek,
and Nathan James Sanders.
Current Biology, Volume 26, Issue 3, 8 February 2016, Pages R87-R91
https://www.sciencedirect.com/science/article/pii/S0960982215015754

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