Structure Polish Academy of Sciences

Certain species of fish, crayfish or squirrels, non-native in Europe, are among the most dangerous invasive alien species that can be detrimental to the EU’s environment. Most of them come from the tropical zone and have little chance of survival in Poland – says Dr. Wojciech Solarz from the Institute of Nature Conservation of the Polish Academy of Sciences in Kraków.

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In the study, under the direction of Prof. Helen Roy from the UK Centre for Ecology and Hydrology, over 40 scientists from around Europe were involved. They estimated the probability with which these alien species are likely to arrive, establish, spread, and have negative impact on the Europe’s biodiversity over the next decade.

The highest proportion of potentially dangerous for the EU's natural environment species originate in Asia, North and South America. Aquatic species can be accidentally introduced in Europe mainly via long-distance shipping, while terrestrial invertebrates are most likely to arrive along with imported plants. The Mediterranean, Continental, and Atlantic biogeographic regions (volcanic islands off the coast of Europe and Africa) are predicted to be the most threatened across all taxonomic groups, while to the Baltic, Black Sea and Boreal regions are least at risk. It also seems that no new alien species threaten the high-mountain ecosystems – experts assessed.

The eight species (seven animals and one plant) that pose the highest risk are:

Channa argus – the northern snakehead is a fish native to China, Russia and North and South Korea. Currently, it can also be found in shallow, marshy ponds and wetlands in Japan and Florida.

Plotosus lineatus – the striped eel catfish originating from the Indian Ocean. In 2002 it was noticed in Mediterranean waters and quickly spread along Israeli coast , especially in shallow waters with sandy or muddy bottoms. This fish produces toxins that are potentially dangerous to humans. From the environmental point of view, its presence may cause decline in native fish populations through competition and displacement.

Limnoperna fortunei – it represents the mussel family. It comes from China and Southeast Asia; in 1965 it appeared in the waters of Hong Kong, and in the 90s also in Japan and Taiwan. With time, it invaded the US and South America. It affects the local fauna and food networks in fresh water.

Mytilopsis sallei – the black striped mussel that comes from the coast of Panama, but has spread in the waters of the Indian and the Pacific Ocean, reaching Fiji, India, Malaysia, Taiwan, Japan and Australia.

Crepidula onyx - snail originating from the waters of California and Mexico. It is now widespread and considered a highly invasive in Asia. His presence was recorded in Korea, Japan and Hong Kong.

Orconectes rusticus – it is a large and aggressive species of freshwater crayfish, native to the US. Because of its invasive behaviour over the past fifty years the rusty crayfish has become the dominant species in the Midwestern United States.

Sciurus niger – the fox squirrel, native to North America, competes for resources with other species of squirrels (S. griseus). It is also potentially dangerous for our red squirrel (S. vulgaris).

Codium parvulum – green seaweed native to the Indo-Pacific Ocean. It is already present in the Red Sea and Mediterranean. It is believed that the presence of this plant affects the structure and functioning of ecosystems.

"Most of these species come from the tropical zone, and even if they arrive to Poland, they have little chance of surviving," said Dr. Wojciech Solarz from the Institute of Nature Conservation of the Polish Academy of Sciences (PAS) in Kraków, who was involved in the work of the team developing a list of invasive species.

He points out, however, that alien species can be dangerous to nature even if they are not at home in a new place. Even in this case, there is a risk of transmitting diseases or parasites through it.

"The biggest chance for establishing in Poland have the rusty crayfish and fox squirrels that come climatic zones similar to ours like North America. In the longer term, their presence could mean competition for native species, transfer parasites or diseases to them, even cause economic losses," says Dr. Solarz.

He noted, however, that none of these species has been reported in Poland for now and there are no indications that these species are raised in our country.

The above mentioned species are listed as the top eight invasive species out of 329 that pose threats to the EU's ecosystems. A complete list is provided in the "Global Change Biology" journal. The study was financed by the European Commission.

It is estimated that there are already over 14 000 alien species in Europe, of which more than half come from non-European regions.

A large part of alien species is spreading along trade routes. Others are intentionally imported for breeding purposes, consumption or as pets - Dr. Solarz points out. This was the case, for example, with North American crayfish: spinycheek (Orconectes limosus) and signal (Pacifastacus leniusculus), which were brought to Europe for breeding purposes, and then released into the wild or escaped. Both of these species are carriers of water molds that causes crayfish plague, which is lethal to European crayfish.

Although it is impossible to completely eliminate the proliferation of alien species - it is worth trying, because they often pose a threat - says the scientist. According to the Red List of Threatened Species – over 200 species have gone extinct due to the introduction of invasive alien species. In Poland, the problem is, among others, with American mink, racoons and raccoon dogs, which can wreak havoc on ground-nesting birds.

Dr. Solarz pointed out that at the very top of the list of alien species threatening the EU’s environment there are only two potentially dangerous for Poland. The North American bison (Bison bison) was recognized as a big threat, especially to our native European wood bison (Bison bonasus) which still belongs to endangered species. The world’s population of European bison is smaller than the population of white rhinoceros – points out Dr. Solarz.

Invasion alien species are considered to be the second most important reason for biodiversity loss (after direct habitat  loss or destruction). In addition, they cause enormous economic damages, which in Europe alone reach at least EUR 12 billion a year. According to Dr. Solarz, creating a list of alien species potentially dangerous for the EU’s ecosystems is of a preventive nature. Currently, there are 49 species on the list that are not allowed to import, keep, breed or sell in Europe. If they were found in one of the EU member states – the country is obliged to take actions that will eliminate the species or prevent its expansion – explains the scientist.

Source: www.naukawpolsce.pap.pl