Saturday, 28 May 2011

Ragwort conservation ecology

First of all in this posting. Just to recap, ragwort is a problem in hay, but as is explained in this posting about a piece of real ragwort nonsense, they avoid it elsewhere. Animals are designed by nature to avoid poisons, and the poisons in ragwort are present in 3% of all plants most of which we never hear about. We don't have all the campaigning, the commercial outfits making false claims and the accompanying hysteria about the others. We know that ragwort poisoning is rare. We know this because of the research.

The purpose of this blog entry is to deal with the latest piece of misinformation that has appeared on a facebook discussion group. It repeats a couple of falsehoods. Firstly you get this comment from one user

You have to report it

This is most certainly NOT the case.

It is dealt with on this blog entry and chapter and verse is given from the mouth of a government minister on this entry about "Notifiable weeds " ( There is no such thing in the UK.)

The second claim made on that forum is more complicated, but the answer is just as clear.

Most entymolologist (sic) probably wouldn't view the loss of ragwort habitat due to grazing land management as detrimental.

If an entomologist were at all knowledgeable about ecology and population dynamics then he or she would be very concerned.

First of all before I explain the science you have to realise that this goes much wider than ragwort. The unnecessary panic about ragwort means that, as has been documented, plants get misidentified and targeted and also the general spraying, ploughing and general agricultural intensification it causes affects all wild flowers and the wildlife dependent on them.

The central concept here is calles by some wonderfully technical words "Metapopulation dynamics." Metapopulation is one of those words that we wildlife specialists like to come up with. It is half Greek and half Latin, but the general idea is quite simple.

Wildlife of all kinds tends to exist in patches of habitat and the survival of any of the species depends on how close these patches are to each other and how many of them are close to each other.

So we have this patchwork. If you start taking pieces out of the patchwork you start destabilising them. Losing chunks of habitat has an effect beyond just losing those chunks. The loss effects all the habitat in the surrounding area too. A central feature of this is that an organism can be extinct before all the habitat is gone.

I am simplifying things a bit but this is the essence of the issue here. You can read up further if you like. One of the standard textbooks actually has a whole chapter on an aspect of ragwort metapopulations but be warned it has been used as a textbook on a course for a Masters level degree. It is the sort of thing that wildlife nerds like me take to bed. (Actually I am really a sociable extrovert, but I do like my science books!)

This is one of the reasons we are seeing massive declines in UK wildlife. We have lost a third of our moths since the later 1960s, we see declines in birds too and all because of the decline in habitat.

It is worth mentioning at this point that many rare insects live on common plants, this includes ragwort. They have complicated requirements. Ecology is like that. The presence of a species may depend on many factors, site dryness, wetness, sunshine ,shade, the absence of food for other species that are affected by the same parasites or predators etc. etc.

Now to recap and explain. The loss of any habitat, including that on grazing land has a detrimental effect. We know this for certain because of all the research that has been done. We know this because of central tenets of modern biology.
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