Lois’s answer to “It's occurred to me that, when Penric stays anywhere for a while, there may be a significant decrea…” > Likes and Comments

Thanks for the reply. Yes, I realized that no species is in any danger of extinction by sorcerer; but Penric could make a significant difference to the population in his locality, over a period of time, and I'd be fascinated to see how the indirect effects of that played out—could be good, bad, or some mixture. Reintroducing wolves into Yellowstone reduced the local elk and coyote populations, but increased the fox, beaver, and grizzly bear populations, and also indirectly affected plants, rivers, and fish.

I'd like to chime in here as well, despite that I am no ecologist (as are the other participants in the discussion). With ecology, however dramatic the effects of a change, the "do not touch a running system" principle cannot be applied, because the ecological balance is fiction, change is constant. Yes, people bring change at supersonic rate, which is extemely disruptive. But Penric is only one person, he rather dwells in his study, and he only gets rid of a few very specific species of instects. I got in another argument today, because of large-scale farming, glyphosate (or any pestiside at all) and bees, of all things. So, the other non-ecologists suggest that we should stop killing bees, fullstop. And then I am feeling mad, in the sense of going stir crazy. Because I am currently trying my hand at gardening, with some courgettes, tomatoes, and also parsley. The parsley is fairing badly. Also, I am not using any herbisides, pestisides, or other chemicals. And I see why the large-scale farming which delivers food to people who are not farmers does need them. But no, bees (I like bees, btw). So again, informed advice is required - as usual. What is the function of flies? Do they pollinate plants similar to bees? (Which, of course, is not bees' primary function, it is a side effect of their attempt at survival). Do they have any role in decomposing anything? Or are they just using the residual heat? Or whatever? Are wolves and flies comparable in any meaningful way? I think not. I don't think Penric's killing of flies will produce any noticeable ecological effect over the time of his hopefully very long life. Not one bit.

Wikipedia: "Houseflies play an important ecological role in breaking down and recycling organic matter … Houseflies have many predators, including birds, reptiles, amphibians, various insects, and spiders." Presumably a shortage of flies would have some effect on these predator species, if only in forcing them to look for alternative food.

I don't think Penric limits his attentions to specific species. From his or Desdemona's point of view, any species will do as long as no god cares about it; and that seems to cover quite a wide range.

Well, if not flies, the birds, reptiles, amphibians, various insects and spiders will have to eat other types of insects, of which there is no shortage. Crickets, maybe. The very important role of breaking down organic matter can certainly be assisted by other organisms, of which worms spring to mind, but doubtless there are enough others. We will have to check again in Wikipedia, but I think that flies do not occupy a unique ecological niche. Also, Pen will also eliminate the flies in his immediate surroundings, where presumably the prevalent life form are humans, and so no amphibians will suffer lower supply. Ecosystems are usually larger than two human villages and a fort, Pen cannot be everywhere at once, and thus our efforts here are perfectly futile. Flies respawn very quick;y, not sure how quick exactly for the different species, eggs and larvae are likely involved... etc. etc., Penric doesn't meddle with the whole cycle, only killing off mature individuals, of which at least one part has already been able to procreate before meeting their unnatural end. Poor Penric, he really plays by the rools and does the dirtly work himself, thus not making a dent in the flies' population in the long run. At least, nothing can grow immune to demon magic, if it works, it works.

Most amphibians are frogs and toads, which can live near humans.

It seems to me that Penric clearing all out all the bugs in his vicinity frequently for a period of years is likely to have some ecological effects; but I have no idea what the effects would be, nor whether they'd be visible to humans.

It was established right from the start (in 'Penric's Demon') that he and Desdemona don't just kill flies, but also, for example, fleas, ticks, beetles, lice, and moth eggs. When in need of something larger, they've been known to kill rats, cats, dogs, pigs, cattle, horses, whatever.

Oh, and seagulls, of course…

I am known to not tolerate flies in my house, for which I have screens and do tolerate a few spiders. I am treating all the cats for ticks with a chemical which is supposed to clear the garden of them too (of ticks, not cats). We currently do not have lice or bedbugs. Or fleas. How is this different from Penric's situation? Needless to say, the cats are eradicating rats, mice, larger bugs, frogs, snakes and birds rather swiftly. If you insist on talking ecology, let's say that obviously he will achieve fewer vermin in his household.

Oh, and I am no vegitarian.

Brzk: Of course you and your cats are also having some effects on your local ecology, although keeping flies out of the house with screens must have almost no effect on the flies. If the screens are effective, they can't enter the house, but they're free to lead normal lives outside the house.

Yes, we are all ecology. You can count we as three hungry amphibians.

Hi all! I thought I’d chime in here because I am an ecologist. I specialise in parasite-host interactions and a lot of my research shows the benefits, especially to immune system function, of parasites. The other interesting thing I have found is that true parasites are actually rare, most parasites actually move along a kind of continuum between parasitic behaviour and mutualistic behaviour. Anyway, Jonathan Palfrey asked about “indirect effects”, and if you reduced the population of say fleas, lice or ticks too low or eradicated them, the flow on effects could include immune system failure (allergy cascade, autoimmune disease) and the emergence of novel interactions (like diet switching to something more abundant as in when mice switch from seeds to grasshoppers when there is a locust plague). One of the greatest examples of the strange interaction between immune function and parasites is found in sheep. Sheep that are drenched and drenched and drenched for intestinal worms lose the ability, genetically, to mount an immune response and this, surprisingly, results in finer wool. So now we know that the thick wool response is due to not only genetics but an inbuilt immune response. Killing off of other “pests” like mice or rats would then reduce the success of species that depend on them, like snakes, owls, foxes, hedgehogs and the like. So there would be an ecological flow on effect (although I suspect the Bastard would ensure that such an event wouldn’t happen). Next, Brzk asked “what is the function of flies”, and you guessed right, most flies are generalist pollinators, and if we didn’t have flies, we wouldn’t have very good returns on many crops or wildflowers or forests. These flies also keep aphids under control, so win-win for farmers. There are many types of flies, the pollinators are often hover flies and the decomposers are flesh flies or blow flies, and they all serve an ecosystem function. Penric killing off all the stable flies in an area wouldn’t do much because there’s always more stable flies somewhere else, and the area would get recolonised very quickly. These sorts of flies can fly long distances in search of faeces. And finally, Jonathan Palfrey mentioned seagulls, one of my favourite groups of birds BTW! There are over 50 species of gulls in the world ranging in size from the dainty Little Gull with its pretty black head (about 100g) to the very large Great Black Backed Gull (up to 2kg) and most are predators of fish, shellfish and krill rather than scavengers. We humans just notice the scavengers more because they tend to live around humans. So, if Penric were to inhabit an area for a long time, he’d have to be careful about disrupting the normal ecological function, but I reckon that people bringing in vermin (like at the brothel) would keep him plenty busy.

Thank you for joining the discussion, Terngirl! Most interesting fact, the one about the sheep - to genetically lose the ability for an immunce response is no small thing. (I knew that the immune response can be "trained", but never suspected that the lack of training may have such severe consequences). If you ever find the time or inclination to share your views on the mass desctruction of bees (collateral damage), I would be interested to hear them.
It is nor surprising that amongst Lois's readers there is an ecologist - representatives of the scientific (way of life?) likely comprise a larger portion of Lois's followers than those of other authors. Great!

Thanks, Terngirl! That's all interesting. Yes, of course there will always be more 'vermin' coming in from elsewhere (unless they learn to avoid that Place of Death!), but it seemed to me that daily exterminations in one locality over a long period could significantly reduce the local vermin population; and Penric probably shouldn't assume that this would have no consequences.

Agreed! Any perturbation could have unintended consequences — but I believe the Bastard would figure it out and prevent it! Or maybe the Mother, wouldn’t she be in charge of ecosystems? Or the Daughter?

"The gods have no hands in this world but ours. If we fail Them, where then can They turn?" (Ingrey kin Wolfcliff, The Hallowed Hunt, quoted at the beginning of The Physicians of Vilnoc)