Species Of The Week Number 40: Ragwort
Our most controversial species to date?
We have plenty of native Ragwort in Meanwood. We also have horses in Meanwood. In 2003 an influential report stated Ragwort poisoning killed 6,500 horse every year and the plant should be removed . The report was widely publicised and the danger of Ragwort to horses has become accepted common knowledge.
However, the 'science' behind the report was based on a very small sample size and a flawed methodology. The authors translated 'possible poisonings' in a survey - to which only 4% of equine vets had responded - into reports of death. They then multiplied the results by the total number of vets there were. They didn't consider the possibility, for example, that vets didn't respond to the survey because they hadn't seen any poisonings.
Ragwort certainly isn't risk free - it is mildly toxic (so are many plants) but other research shows significant risk to horses only when it is dried as hay and/or consumed in large quantities. We don't know exactly how many horses die each year from Ragwort poisoning, if any, because it would need post mortem examination. The best evidence from abroad suggests very low numbers.
Also, Ragwort tastes bitter and horses actually avoid it unless there really is nothing else to eat. A horse needs to consume between 2% and 7% of its bodyweight for Ragwort to be fatal. That's a lot of Ragwort (or a tiny horse).
In 2007 Leeds City Council was spending £14k per year on Ragwort removal. I don't know what the situation is now with the increased awareness of biodiversity, but to this day Ragwort remains the only native species that the Council says you shouldn't put in your brown bin (if indeed you have one).
The Ragwort flowering in Meanwood is, conversely, a vital part of our ecosystem. A non-scientific survey by me this week found lots of bugs and creepy-crawlies using our Ragwort as their home or food source. The list included Meadow Brown and Large Skipper Butterflies, rather stunning Thick-legged Flower Beetles and Red Soldier Beetles, Red-tailed Bumble Bees, Black Ants, Ragwort Fly, 7-spot Ladybird and Potato Myrid. There were a few other bugs I couldn't identify accurately. Ragwort is also known to be the home and food source of the colourful Cinnabar Moth, but I didn't spot any of them this time.
Some of the photos were even taken in fields that had horses in them. Apparently all still alive.
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