According to a recent study, some three percent of the country's spider species have died out and about 50 percent are threatened with extinction. What are the reasons behind the spiders' disappearance? And is it true that there are poisonous spiders migrating to the Czech Republic from the south of Europe?
These are just some of the questions I put to biologist Milan Řezáč of the Crop Research Institute, who is one of the authors of the study. But I first wanted to know just how threatened spiders in the Czech Republic are:
“Currently we know about 27 species that have probably gone extinct in the Czech Republic and there are another 92 that are close to extinction, which means that they will probably die out in the near future. So I would consider the situation to be really dangerous.
“But of course it depends on your point of view. Some people are more interested in historical monuments. People are horrified when they see videos of IS members destroying archaeological sites.
“But let me remind you that while these sites are about 2,000 years old, every single spider species is several million years old, so in my point of view it is really sad that we are losing the variety of species and I definitely consider it a serious problem.”
How long have you been monitoring the situation?
“The first data about spider fauna in the Czech Republic is about 200 years old. But of course the research is getting more and more detailed with time, so I would say that for the past four decades we have had really detailed information.”
How long have the spiders been threatened?
“I would say that majority of species that are now considered extinct have disappeared over the past fifty years. It is probably related to the change of farming in this country, which started with collectivisation of Czech farms during Communism.
“There was a tendency to make fields larger and to eliminate the habitats surrounding the fields that were actually harbouring majority of the species. But this trend has accelerated in recent years and we can really see the species disappearing from our landscape.”
What are the other major threats to spider populations?
“Every single spider species is several million years old, so I think it is really sad that we are losing the variety of species and I definitely consider it a serious problem.”
“There are some, let’s say more cryptic reasons why species disappear, for instance the overuse of agrochemicals such as pesticides. But really the main cause of losing the diversity is changing of the habitat structure of our landscape.
“Let me compare our nature to a garden. When you don't manage your garden, many species will disappear, and the same thing happens in nature. The gardeners in central Europe used to be big animals, mainly herbivores, who were grazing the grass and allowed the species who were weak in competition to sustain there.
“Originally these big mammals were wild and later people replaced them with domesticated animals, who did the same job. But nowadays, this kind of management is not interesting to people and it causes an overwhelming overgrowth of landscape with plants and aggressive grasses that really push away many species.”
Would people actually notice several spider species going extinct? What are the consequences of their disappearance?
“Every species is connected to the other, so when one species dies out it affects the others. So for instance parasites that live off these specie die out as well, the predators who feed on them are also harmed.
“On the other hand the population of the spiders’ prey expands, which is something we should be concerned about. Because spiders eat mainly insects and many insects are actually pests.
“So when the spiders are disappearing, there are outbreaks of pests and it has been scientifically proven that a rich community of spider species is more able to deal with pests on crops than just a few species.”
Do they encounter the same problems in the rest of Europe?
“It is actually a problem that concerns the whole of Europe, but there are some differences. For instance in Western Europe there is more advanced nature conservation so they know more about biology of particular species and they already do something to protect them.
“There are also countries with very different socio-economic situation, such as in the south of Europe, where traditional farming is still present. So species that are already extinct in the Czech Republic can still be found in other parts of Europe.”
Are Czechs doing something to reverse the trend? Are there some initiatives that specialise in protection of spiders?
“Unfortunately we are at the very beginning but you can already see some activities. There are several spider species which were suggested to be protected by law.
“There are some nature reserves that were established with the aim to protect endangered spiders. One of those is actually in Prague, a small wetland in Klánovický les in the eastern part of Prague. And there are also some organisations that aim to re-introduce traditional ways of farming to the landscape.
“The goal is to manage the landscape as a garden, to cut the grass, to keep the habitat open, to harvest the biomass and to eliminate the overuse of fertilisers. Actually it is interesting that the result is something that people would consider a beautiful landscape. So spiders actually like what we consider beautiful.
“The problem is that people, at least in the last decades, lost the ability to see the beauty of their countryside and they prefer to pay for expensive holidays abroad. They don't seem to care much about what is going on beyond their houses.”
How many spider species can actually be found on the territory of the Czech Republic?
“There is just a small number of species living in the Czech Republic that can really bite you and these don't cause any serious consequences.”
“We know about almost 900 species in the Czech Republic, which is a pretty high number. All over the world we know about 50,000 spiders but the number is probably much higher, since some areas, such as tropical rainforests, are not very well researched. But the Czech Republic is one of the best researched countries as far as spiders are concerned.
Why is that?
“It’s a historical coincidence. We had some scientists who were very active in studying spiders. I would say that Britain is the best researched country in terms of spiders and we are the second best.”
Are there any locations that are particularly rich in spider populations?
“Spiders like regions that are variable in habitats, so landscapes with a strong relief are suitable for them. So in central Bohemia it would be the region of Křivoklát, in north Bohemia it would be the Krkonoše mountains and in south Moravia it would be Pálava.
“South Moravia is really rich in species because there are many thermofilic species that live mainly in the Balkans but their border of distribution reaches up to south Moravia. Interestingly even Prague is very rich in spider species. In Prague we have around 500 species, which is a lot.”
Are there any poisonous spiders living in this country? I have heard that there are certain species moving from southern Europe.
“No, spiders are still safe. To be honest almost all of the spiders living in the Czech Republic have a venom gland. But the venom is adapted to kill or paralyse their prey, usually insects, and it is not harmful to mammals. There is just a small number of species that can really bite you and these don't cause any serious consequences. I would compare it to the sting of wasps or bees.
“There are some species that can cause some trouble, for instance velvet spiders, very rare species living in rocky steppes and in slopes of rivers. I was bitten by them several times when I studied them and it cause me very fast heart beat and my face turned purple, but luckily it lasted only for about an hour.
“Another case would be the only spider living in water, Argironeta Aquatica. This spider is also large and it can bite you, but you would be really lucky to encounter it, since waters in the Czech Republic are really polluted nowadays and there are only a few lakes with clean enough water to harbour the species. So it's really difficult even for an arachnologist to find them.”
Still, has this migration of southern European spiders actually taken place?
“There are some cases of recent migrations to our region and it is interesting that all these spiders have something in common. They like warmer environment so it seems that it is really related to global warming.
“Some of them are large and some of them can bite. You. There is one species, it is called Cheiracanthium Punctorium, in Czech it is zápřednice jedovatá, which means a venomous spider. This spider can cause something like a bee sting so there is no reason to be afraid of spiders in the Czech Republic.”
Finally, you have recently published, along with your colleagues, a book about spiders. Can you tell me more about it?
“It is an atlas of Czech spiders which covers all the nearly 900 species living in the Czech Republic. And I think none of the other European countries has such a comprehensive atlas, so you can get a really good idea of how diverse the spiders are.
“I hope the book will give the wider public a better insight into the world of spiders. And I would be really happy if some small boy or a girl would buy the atlas and become a fan of spiders. This is the main reason why we published the book.”
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