Scientists have assessed the risks of the global spread of "migrant mollusks."

The results of the research have been published in the scientific journal Hydrobiologia. Biological invasions refer to instances of intentional or unintentional introduction of specific animal and plant species into new countries and continents. Due to globalization, the "export" of species from one country to another has become a widespread phenomenon.

Often, these organisms are not deliberately and consciously spread by humans but travel on their own, using human transportation as "stowaways." For instance, a significant number of marine invertebrate species have migrated from one ocean to another by entering the ballast water of ships (water is taken on in one port and discharged in another, sometimes thousands of kilometers away). This is how jellyfish, crustaceans, and mollusks with free-swimming (planktonic) larvae spread.

Such migrations not only disrupt the structure of natural ecosystems and harm their functionality but also have significant practical implications. For example, in the 20th century, the arrival of the Colorado potato beetle in the USSR created problems for agriculture.

However, in recent times, the frequency and impact of such events have increased dramatically. A distinct biological discipline has even emerged—ecology of animal and plant invasions. In particular, foreign species of mollusks provoke changes in ecosystems. Although they are generally considered to be sedentary creatures, they actively spread across the Earth at rapid rates. The issue of invasive mollusk species has reached such a scale that scientists worldwide participate in monitoring studies conducted approximately every 10-12 years, allowing for tracking the spread of these animals and preventing potential risks to the planet's ecosystems.

In the latest such monitoring, Maxim Vinarsky, head of the laboratory of macroecology and biogeography of invertebrates at St. Petersburg State University, participated. The researchers conducted a global mapping of invasive freshwater mollusk species, assessed current research trends in this field, and gained insights into how many such species currently exist on Earth and how their abundance is distributed. Furthermore, biologists analyzed the main risks associated with invasive species as well as the most crucial methods for preventing, detecting, and monitoring such invasions.

“The work was carried out using an expert survey method, where each co-author was assigned a specific fragment of the topic while simultaneously participating in discussions of parts written by other co-authors. As a result, we achieved a holistic view of the entire picture, reflecting the collective understanding of the situation by leading specialists in the field,” said Maxim Vinarsky.

The Russian part of the study, conducted at St. Petersburg State University, included data from the territory of the former USSR and neighboring countries. Scientists working under Maxim Vinarsky are leading experts on invasive freshwater mollusks in Russia. In recent years, they have published a series of articles on this issue.

Among the main risks highlighted by specialists is the deterioration of the medical-parasitological situation in certain regions. Many species of freshwater mollusks serve as intermediate hosts for parasitic worms—trematodes—and facilitate the "relocation" of parasites and their spread in new territories. Some of these may potentially pose a threat to humans.

Furthermore, some invasive mollusk species enter into competitive relationships with native species and often displace them, occupying their ecological niches, which significantly alters biological diversity. For example, mollusks of the genus Dreissena form dense colonies in water supply systems, disrupting communication networks, while some tropical species of alien snails (such as the well-known ampullaria among aquarists) can act as agricultural pests in rice fields.