The serious and growing threat posed by biological invasions to biodiversity and livelihoods means that public engagement in dealing with problems of invasive alien species is ever more urgent and necessary hence a citizen science experiment was carried out in north-eastern Italy. The study aimed i) to raise awareness of invasive alien species threatening trees and forests, and ii) to perform monitoring activities of a group of wood borers as an example, involving teachers and students (aged 11 to 18) of high schools. Students and teachers were given background knowledge and trained about the protocol for collecting data in schoolyards/grounds. Native (Anisandrus dispar (Fabricius, 1792), Xyleborinus saxesenii (Ratzeburg, 1837)) and exotic ambrosia beetles (Anisandrus maiche Kurentsov, Cnestus mutilatus (Blandford), Xylosandrus crassiusculus (Motschulsky, 1866), Xylosandrus germanus (Blandford, 1894)) were used as the target species, as they could be easily detected through accessible and low-cost traps requiring limited effort. The traps were exposed for 24 hours weekly between March and June 2021. The experiment also aimed to strengthen public involvement, connecting environmental education and experiential outdoor learning. The mutual collaboration resulted in a wider knowledge of the potential impact of exotic species. It also led to new geographical citizen-science records of two alien ambrosia beetles considered to be quarantine pests by the European Union: C. mutilatus, new for the European part of the EPPO (European and Mediterranean Plant Protection Organization) region, and A. maiche, which was previously found only in Eastern European EPPO member countries.

Anisandrus maiche, Cnestus mutilatus, environmental education, first record, invasive alien species, knowledge, students, surveillance

Humans have traded and transported alien species for decades, intentionally or unintentionally, but, over the last 50 years, the rates of Invasive Alien Species’ (IAS) introductions have significantly grown and currently do not show, at a global scale, any sign of saturation (Hulme 2009). Instead, the trend is increasing, especially for insect species mainly introduced accidentally as stowaways or contaminants (Hulme et al. 2008; Seebens et al. 2017; Kenis et al. 2019; Turbelin et al. 2022). The introduction of IAS as contaminants may be predicted from their pathways, e.g., by plants, fruits, or wood (Kenis et al. 2007; Hulme et al. 2008; Pergl et al. 2020). Or stowaways can arrive independently of a specific commodity, as hitchhikers on ships, in containers, vehicles (car, train, airplane), packing material, and in the luggage of tourists (Hulme et al. 2008; Pergl et al. 2020; Turbelin et al. 2022). Identifying and managing the pathways through which IAS arrive and spread is an important component of any strategy aimed at reducing the threat of biological invasions but difficult to carry out (Roques 2015; Seebens et al. 2017; Pergl et al. 2020; Turbelin et al. 2022). Consequently, given sets of gaps that regulations cannot cover, the direct involvement of the wider public in the surveillance and management of IAS is crucial (Hulme et al. 2008; Faulkner et al. 2020; Turbelin et al. 2022).

Citizen science, which Pocock et al. (2019) defined as “the involvement of people in the scientific process, including participating in environmental recording and monitoring”, represents an opportunity to raise awareness of common problems of biological invasions and to expand better monitoring efforts conducted by researchers and phytosanitary personnel in detecting IAS (Sagy et al. 2019). IAS exemplify an excellent case of citizen science application as they threaten the environment and society (García-Llorente et al. 2008; Novoa et al. 2017). Increasing the public’s perception of IAS is essential (Jubase et al. 2021) and it has been shown that after educational and informative efforts the public was much more aware of IAS (García-Llorente et al. 2008). Actions aimed at increasing public knowledge and awareness, such as workshops, training programs, or media involvement, must be supported in policy decisions and by funding (García-Llorente et al. 2008; Novoa et al. 2017).

In particular, educating and training school students in IAS has become a commonly recognised innovative and holistic approach because students bring home the message and share it with relatives, in this way supporting intergenerational learning (Verbrugge et al. 2021). Among IAS affecting trees and forests, bark and ambrosia beetles (Coleoptera Curculionidae Scolytinae) represent an important group and have already been used in a citizen science initiative, called ‘Backyard Bark Beetles’ (Steininger et al. 2015). The purposes of our study were to implement a large-scale surveillance and increase high school students’ awareness about two recently reported ambrosia beetle species (Anisandrus maiche Kurentsov, 1941 and Cnestus mutilatus (Blandford, 1894)). This paper aims to disseminate how environmental education can strengthen public engagement and contribute to IAS detection.

Our study aimed to both educate students and collect scientific data at sites such as schools where surveillance for potentially invasive ambrosia beetles is not usually conducted, or where it is sometimes misunderstood. Student involvement and curiosity were aroused during a pre-survey lecture where we stressed the importance of their role in assessing the unknown species and abundance of ambrosia beetles in their school yards/grounds, and the potential occurrence of undetected invasive species that could pose a serious threat to trees and forests in the surrounding environments. The results obtained provide strong evidence covering all prior expectations.

The citizen science approach contributed important goals for monitoring and alien species detection. Six different species of ambrosia beetles were recorded during the present study, two native species, A. dispar and X. saxesenii, and four alien species (35% of the total catch). Xylosandrus germanus and X. crassiusculus were accidentally introduced into Italy in 1992 and 2003, respectively, and are present in some deciduous temperate forests of the Veneto region (EPPO 2010; Rassati et al. 2016), whereas C. mutilatus and A. maiche were both first records in Italy and first and third records, respectively, in the European part of the EPPO region (Colombari et al. 2022; EPPO 2022).

Among ambrosia beetles, X. saxesenii, X. germanus, and X. crassiusculus were the most represented and our results are consistent with previous research using bottles and ethanol-based lures (Miller and Rabaglia 2009; Reding et al. 2011; Werle et al. 2012; Steininger at al. 2015; Tarno et al. 2021). In particular, ethanol has been demonstrated to have a significant effect on X. saxesenii, which usually accounted for the greater percentage of the overall catches (Oliver and Mannion 2001; Miller and Rabaglia 2009; Galko et al. 2014; Steininger at al. 2015; Chen et al. 2021; Cavaletto et al. 2022) as our data confirm (62.2% of the total number of individuals collected). By contrast, the only other native species, A. dispar, was scarce even though it is lured to ethanol-baited traps, and it often represents alongside X. saxesenii one of the most trapped ambrosia beetles (Galko et al. 2014; Holuša et al. 2021). The two new species found and confirmed as successfully established, C. mutilatus and A. maiche, are known instead to respond almost exclusively to baits containing ethanol alone (Sweeney et al. 2016; EPPO 2020) and are significantly more attracted to bottle than to funnel traps (Klingeman et al. 2017; Miller et al. 2018; Tobin and Ginzel 2022).

Different catches indeed can be interpreted as the complex result of many variable factors that can affect trapping rates such as, among others, the aggressiveness of the species and their preferred host condition for attack and/or breeding (Oliver and Mannion 2001; Chen et al. 2021). Anyway, none of the overall species recorded were aggressive, able to attack healthy trees, but were instead associated with stressed (X. saxesenii and X. germanus), weakened (X. crassiusculus and Hypothenemus spp.) or dying hosts (A. dispar) (Chen et al. 2021; Holuša et al. 2021). Although C. mutilatus and A. maiche are classified as non-aggressive because of their preference for unhealthy (stressed and weakened) or recently dead small diameter materials, their low host specificity may raise concerns for forest ecosystems and particularly for nurseries, plantations, ornamentals, and fruit trees (Klingeman et al. 2017; EPPO 2020; Chen et al. 2021; Tobin and Ginzel 2022).

Diversity in species richness and abundance among sites was best predicted by sampling effects as more individual, and thus more species were caught where the monitoring effort was more prolonged (McCabe 2011; Brown et al. 2016). Thus, we cannot exclude that more species could be present at those sites where a low number of individuals was sampled and well aware of a bias in our analyses due to method we used, i.e., the ethanol-based lure known to be less attractive to host-specific bark and ambrosia beetles (Miller and Rabaglia 2009; Steininger at al. 2015). The time dimension in a sampling program is of great importance, as it considers temporal dynamics and phenological maturation of populations (Binns and Nyrop 1992). At the site where the monitoring period lasted more than two months, species richness and abundance were the highest, but considering the sites that collected no beetles at all, only in one case out of three a likely explanation was the methodological limitation. In the other two cases, sampling effort was not so different from that of other schools.

Undoubtedly, at the small scale, abundance and species richness are sensitive to sample size, but they also vary naturally, being affected by many geographic, abiotic and biotic factors such as resource availability, environmental heterogeneity, and ability to disperse (McIntyre et al. 2001; Brown et al. 2016). This is particularly true for dynamic and vulnerable urban ecosystems, where free movements of goods linked to population density can act as another driver influencing the occurrence of beetles (McIntyre et al. 2001; Branco et al. 2019; Meurisse et al. 2019; EPPO 2020). The complex interactions among all these local and landscape factors must be studied further for a better explanation of our results.

Questionnaire results showed that students acquired a greater knowledge and increased their awareness and interest by on average +57%, +40% and +55%, respectively, changing their attitude about IAS. At the beginning of the project, less than one third of the students were “aware” of biological invasions and their impact and were able to list some IAS, whereas a large majority of respondents were “unsure”, a result in line with the research of Waliczek et al. (2017). It must be considered, however, that there is a great deal of confusion surrounding some terms and concepts relevant to biological invasion as they are open to subjective interpretation, such as the term ‘invasive’ on which a consensus has not been reached (Colautti and Mc Isaac 2004). If ambiguous, or very technical terminology is used by scientists, for example, invasive and alien species erroneously generate synonyms, which can be expected to create confusion for a lay audience that require a basic understanding of the terms (Verbrugge et al. 2021).

To improve clarity and avoid such unwanted discrepancies that emerged from the results of the pre-lecture questionnaire, during the lecture we devoted time to state key complex terms and concepts in a concise and simple manner. A better understanding of IAS, and a greater awareness of the serious threats they pose, does not always translate into a change in behaviour regarding invasive species (Jordan et al. 2011). Nonetheless, in our case, those students with more positive attitudes towards control and eradication were those “aware” of IAS, as found by Waliczek et al. (2017). These students, being children or grandchildren of farmers, experienced in some way negative/economic impact of IAS and were very knowledgeable about names and number of IAS occurring regionally, in Italy or neighbours’ countries. Family was indeed selected as a reliable source of information, and this is a very important fact on which recent literature focused (Halmatov and Ekin 2017; Masykuroh et al. 2022). Quoting van Noordwijk et al. (2021) “people are more often inspired to change their behaviour if they are influenced by their own social contacts, including friends, family, colleagues, and neighbours”. But the majority of the “aware” students said they learned about IAS mainly from school, as part of biology curricula. However, they amounted to half of total respondents showing that education on IAS at the high school level must improve to gain support for control and management (Waliczek et al. 2017).

After the lecture and once monitoring activities began, almost all students (87%) gave correct answers to questions related to the new topics explained. If we consider that in the pre-test half of respondents answered correctly, the increase in knowledge is 34%, but if we exclude students “aware” of alien species who had probably a greater basic knowledge, then the increase rises to 57%. Waliczek et al. (2018) has demonstrated that delivering comprehensive lectures and laboratory work on invasive species to students led them to perform better in a post-test than students who only attended lectures. The higher content knowledge was likely attributable to the active learning activity, which is known to have a positive influence on further outcomes more than a simple learning method (Verbrugge et al. 2021), and a combination of the two experiences could achieve even better results.

Another very satisfying feedback was that almost all the students enjoyed the lecture and found it an appropriate awareness-raising initiative for gaining new knowledge and greater awareness of the topic. Remarkably, more than half of them would like to learn more, especially about the multiple negative effects related to the introduction of IAS and practices to manage them (limit their spread).

Citizen science empowers school interest when students had to choose their preferred sources of information. Here school was the most favourite, whereas social media were placed only second, which was unexpected given the age of the respondents. Cerri et al. (2022) analysed whether European Union blacklists of IAS with media coverage increased the curiosity of laypersons seeking further information online, and concluded that there were not more visits than expected after the lists were posted. Considering that Wikipedia is the most famous online encyclopaedia largely used by students as a first (and often unique) approach to various issues, this is a noteworthy result highlighting the need for specific education programmes or public awareness campaigns from school level onwards (Hulme et al. 2010; Butkevičienė et al. 2021). Furthermore, the author’s analysis took into consideration invasive alien mammals (such as the raccoon, Procyon lotor (Linnaeus, 1758) and the Eastern gray squirrel, Sciurus carolinensis Gmelin, 1788) that generally arouse interest and are held in higher affection by people, so making eradication and control difficult (Novoa et al. 2017), unlike insects that rarely pose ethical problems. But sensational news or viral videos may greatly affect interest (Cerri et al. 2022) and indeed, after school, TV and social media were selected as second preferred sources of info.

Our results confirm the primary role of education, which has been recognized as a major driver of change in dealing with sustainability challenges (Leicht et al. 2018). For this reason, teachers and environmental educators are expected to reach the knowledge and skills’ objectives required to promote sustainable development (Leicht et al. 2018; Sosa et al. 2021). However, a study of a representative sample of teachers/educators found that half of them had never heard about IAS, or were unsure of the issues, stressing the need for well-trained teachers able to bridge the gap between scientists and students (Sosa et al. 2021; Verbrugge et al. 2021).

The authors would like to thank all the headmasters, teachers and students who accepted the collaboration and collected the data. Special thanks go to headmaster Mario Dalle Carbonare, Professor Michele Zanata and their students (III H and IV H classes, SY 2020–2021; high secondary school “Leonardo da Vinci” – Treviso, Italy) for their enthusiastic participation in the project. Finally, the authors thank the reviewers and editors for all their useful and helpful comments on the manuscript. The monitoring programme was conducted in the context of the European project HOMED (Holistic management of emerging forest pests and diseases), which receives funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 771271.