“Invasions are just part of the global biodiversity problem,” says leading botanist Petr Pyšek

Raccoon dog, photo: 663highland, CC BY 2.5

Raccoon dog, crayfish plague or the giant hogweed - these are just some of the hundreds of invasive animal and plant species that have been intensively spreading in the Czech Republic and elsewhere in Europe over the past years, causing substantial damages to local ecosystems. Seeking to address the problem, the Czech cabinet has just approved a draft bill aimed at regulating the number of invasive species in the Czech Republic. Similar legislation is in effect in other EU member states.

Raccoon dog, photo: 663highland, CC BY 2.5
I discussed the proposal with Petr Pyšek from the Czech Institute of Botany, one of the leading experts on the topic and started by asking on the grounds of what criteria alien plants and animals are classified as invasive.

“Invasive species are a subgroup of non-native or alien or exotic species. They are species introduced by humans outside their natural distribution range, intentionally or unintentionally.

“Some of those species that are brought to new regions actually start to reproduce and establish. Those are species that we call naturalised.

“And the subgroup of these naturalised species that are most successful, which means that they spread at considerable distances from parental plants or they spread fast, are classified as invasive.

“These species usually have an impact ecosystems and biotopes in the invaded ranges.”

How many non-native species are currently registered in Europe and how many of these are classified as invasive species?

“In Europe there was a project called DAISIE carried out over the last decade, which recorded over 10,000 of naturalised species. And several thousands of them could definitely be classified as invasive.

“But as I said, not all of the invasive species have the same impact. They differ in that how threatening they are to the native biodiversity, because the impacts that we record in non-native species are quite diverse and manifold.

“They range from the impact on the native species’ biodiversity, which is the most obvious, because these species outcompete the native species from their communities to impacts on landscape formation, and eco-system functioning.

“It is becoming much easier to get from one part of the world to another, not only for people, but also for other organisms.”

“Some species can also change nutrient dynamics or hydrological regimes and so on. So it depends on particular species and they need to be classified according to what they actually cause.”

So what are the main offenders among invasive plants and animals in the Czech Republic?

“From the plant perspective we have classified about 50 invasive species, of which the most infamous ones are the giant hogweed, Japanese knotweed as well as other knotweed species, black locust, Himalayan balsam and others. In terms of animals its mink, raccoon, crayfish plague, harlequin ladybird and others.”

How hard is the Czech Republic hit by invasive species and is it perhaps more affected than other European countries?

“I wouldn’t say it’s more affected than other countries. One disadvantage could be that we are located in the middle of the continent, so we are getting it from all the directions.

“On the other hand, when comparing the numbers with other European countries, we are I would say average concerning the level of invasion.

“Sometimes the differences are also due to how intense the research is in particular countries and we do have quite advanced science on invasive species so we have good information on what we have. But overall, in European terms, I think we are a standard country.”

What are the costs of damages caused by the invasive species?

“In terms of these damages and impacts, it’s the impact on biodiversity, on the functioning of ecosystem. For invasive animals it’s a sort of predation and hybridisation of plants and animals with native species. We call it corrosion of genetic resources.

Petr Pyšek, photo: Marián Vojtek / Czech Radio
“Economic impacts are mostly recorded in forestry, agriculture and other sectors, but also human health, if we consider species that cause pollen allergies, such as ragweed.

“So in economic terms we have some data of how much it costs, not only for the Czech Republic, but also for the whole of Europe. One estimate from ten years ago was that the annual costs of invasive species in Europe are at least 13 billion euros. It is definitely a conservative estimate, because we do know how costly the effects of invasive species are.”

How fast are the invasive species spreading across the continent? As far as I know, the rate of speed has been increasing in recent decades.

“I am not sure if the rate of speed across the continent has been increasing. It has been pretty fast for the last maybe 40 or 50 years, since the landscape had started to be heavily transformed.

“What is increasing is the influx of non-native species all over the world, meaning the species that we introduce and after that they become naturalised and become a permanent part of the local fauna and flora.

“These numbers are increasing and there is no sign of deceleration. So this is definitely a problem and it applies across all the taxonomy groups, like plants, animals, vertebrae and invertebrate.”

What are the main factors behind this development? Is the climate change or the fact that long-distance travel has become quite common?

“The latter, because it is becoming much easier to get from one part of the world to another, not only for people, but also for other organisms. So the world is shrinking in terms of how fast you can get to another place. That’s one point.

“The annual costs of invasive species in Europe were estimated at 13 billion euros.”

“The other point is increasing trade, because biological invasions are closely related to trade, be it intentional introductions or unintentional introductions as contaminations of commodities.

“But probably the most important thing is that the landscape is changing. The land use is more and more intense, which is associated with the fragmentation of habitats. So it is all of these factors combined.

“Climate change is not so straightforward, because ecological demands of so many species are of course diverse. Some species profit from the climate change. That is quite common for the plants in our region.

“Many plants species are being introduced from areas that are warmer than our climate. For these species it opens the way for rapid spread and future invasion. One example is the ragweed I mentioned.

“Other species may not profit because climate change is also associated with drought, and drought is not really good for plant invasion. So the problem is more complex.”

What can be done to prevent the spread of alien species?

“It is of course an intensive debate and as in other areas it holds that prevention is more effective and less costly than dealing with the consequences.

“It includes various systems introducing cooperation between different countries, in terms of early warning. It also includes recording the species when they appear and trying to stop it before they get established.

“Especially if it’s a species about which we know from other areas that they can be dangerous and that can represent an imminent threat once they get established.

Giant hogweed, photo: Marie-Claire, Creative Commons 3.0
“So targeting these species is really important and it is actually one of the aims of the EU list. The European Union legislation also includes species that are not year widespread but may represent a future threat.”

The government has just approved a bill aimed at preventing the spread of invasive species. Do you think it is sufficient?

“Well the proposal itself is important because it is relevant and approximating our legislation with the EU legislation.

“With the Czech bill there is one problem which we pointed out during the preparation process and it’s that in the previous bill there was a relation to the national list of invasive species and this, as far as we know, has disappeared from the current version that was approved by the government. From our perspective, that’s unfortunate.”

“The problem is that a species that has its natural distribution in one part of Europe and is causing a problem in another one cannot be on the European list. If the national legislation only takes into account the EU legislation, such species get excluded.

“Another thing is that to appear on the EU list, the species has to be approved by all member states. If some member state doesn’t want the species on the list, they don’t get there.

“This is for instance the example of mink, which has not been approved by the Scandinavian countries, where it is an important fur animal, and it’s one of the animals that causes big problems in our region.

“So these species cannot be on the European list but we have them on our national black list. We have such a list and we offered it to the minister to include it but it has disappeared.”

“Such a list would make it possible to fine tune the European list and adapt it to our specific conditions which would make spending the money and working against the invasion more efficiently.”

What else can be done to prevent the spreading of invasive species? And is it to raise awareness about the problem among the general public?

“I think this a very important issue and I think the change can be done by education from a very early stage, in basic and secondary schools, because we really depend on biodiversity.

Mink, photo: Marc Evans, Creative Commons 2.0
“A lot has been said over the past years about the IPBS biodiversity report. And invasions are just part of the global biodiversity problem. If the majority of the public are aware of it, they can push on politicians and things can change.

“In many countries, there are very strong citizen-science movements which involve people in monitoring and recording which is quite easy these days with advanced technological tools like smartphones, which can be used to identify species and report it.

“So this is really important in terms of the early warning and early monitoring systems, so yeas, I think things can be done to improve the situation.”