Naturalists can mediate silent plankton invasions

Plankton can easily spread between water bodies on hydrobiological instruments if naturalists use inadequate biosecurity treatments in their work.

Homo sapiens is not only a great (perhaps the best) candidate for the world’s most invasive species award. Humans, due to their actions and technological wonders, are also at the forefront of good vectors for organismal dispersion. Can we break this inglorious streak?

Because humans will continue to interact with terrestrial and aquatic environments, it is impossible to stop the human-aided dispersal of organisms completely. The best we can do is minimise the risk of human-mediated organism dispersal events by implementing adequate biosecurity methods in our activity” explains Dr Wejnerowski from Adam Mickiewicz University (Poland). 

Plankton sampling using net. Photo by Sandra Wejnerowska

We should be aware that all our activities can affect biodiversity, and adequate biosecurity treatments should be applied whenever the risk of inadvertent spreading of organisms is non-zero” adds Dr Marcin Krzysztof Dziuba from the University of Michigan (United States of America).

Recently, a team of researchers from Adam Mickiewicz University, Istanbul University (Turkey), Åbo Akademi University (Finland), and the University of Michigan empirically proved that plankton net – a basic hydrobiological instrument of almost every aquatic scientist and water manager – is a good vector for the dispersal of various phyto- and zooplankton taxa, including species of high invasive potential. Nuisance, bloom-forming, also toxic filamentous cyanobacteria are efficient hitch-hikers, and they are able to successfully compete with native residents in the new environment.

Instructions for US citizens to avoid spreading invasive species during lake recreation. Photo by Marcin Krzysztof Dziuba

Apart from identifying hitch-hiking plankton on the net and its fate in the new environment, the paper they published in the journal NeoBiota also describes the most commonly used biosecurity treatments that naturalists worldwide use to prevent plankton spread between water bodies via the net.

Their findings sound disturbing: naturalists use inadequate or questionable biosecurity treatments. As revealed by the survey data, only 9% of plankton samplers clean plankton nets using disinfectant liquids after sampling, while a majority of people either rinse the net with distilled or tap water, immerse the net with an open outflow in the water body and let it dry, or do not care about the cleanness of the net after sampling at all.

Exemplary photos of some phyto- (A – Limnothrix redekei, B – Planktothrix agardhii, C – Pseudanabaena limnetica, D – Melosira varians, E – Desmodesmus armatus, F – Asterionella formosa, G – Tetradesmus obliquus) and zooplankton ( H – Keratella cochlearis f. typica) hitch-hikers on the plankton net. Micrograph I shows the plankton biomass on the surface of the plankton net after immersing the net with an open outflow in the water body (inadequate biosecurity treatment). Photos by Tumer Orhun Aykut and Łukasz Wejnerowski. Identification of organisms by Aleksandra Pełechata and Marcin Krzysztof Dziuba.

“Indeed, the reality presented in the paper is unsettling. It worries me when I think of how often I have accidentally facilitated dispersion of nuisance plankton and how much I contributed to the invasion of plankton taxa into new water bodies when using inappropriate biosecurity treatments in my fieldwork,” admits Dr Wejnerowski, and adds: “We do not mean to reinvent the wheel; the problem of aquatic organism dispersal through hydrobiological instruments is already known. For years, it was neglected despite some recalls from the scientific community. It comes back like a bad penny because it needs a complex solution from the society of aquatic naturalists. It should happen. After all, naturalists are a human line of defence, protection and rescue for nature.”

Research article:

Wejnerowski  Ł, Aykut TO, Pełechata A, Rybak M, Dulić T, Meriluoto J, Dziuba MK (2022) Plankton hitch-hikers on naturalists’ instruments as silent intruders of aquatic ecosystems: current risks and possible prevention. NeoBiota 73: 193-219. https://doi.org/10.3897/neobiota.73.82636

Genetically-enhanced biocontrols can help fight large invasive mammals

Genetic biocontrols could rapidly eradicate animals like rats, mice and rabbits. Others – like cats and foxes, would however take a lot longer.

But gene drives are not a one-size-fits-all solution

Invasive alien mammals can have catastrophic impacts on native flora and fauna, causing species extinctions and driving profound environmental change. Classical control methods such as poison baiting, trapping, or hunting are currently not feasible on a large scale, which is why researchers are looking for alternatives.

CRISPR-based genome engineering is often seen as a “silver bullet” for pest control. Despite the increasing interest in the development of this technology for invasive mammals like mice, rats, rabbits, feral cats, and foxes, studies have so far only focused on mice.

Scientists have been pondering whether genome editing technologies could help eradicate larger mammals, and if so, how long it would take.

Rabbit. Photo by Mark Philpott licensed under CC BY-NC 2.0.

In order to address these questions, a team of researchers from the University of Adelaide developed a mathematical model able to simulate the impact of gene drives on mammal populations at a landscape scale. Published in the open-access NeoBiota journal, their study is the first to estimate the time it would take to eradicate long-lived alien mammals.

Using CRISPR-Cas9 technology, the simulated gene drive relies on “molecular scissors” inserted into the Y-chromosome that target and slice up the X-chromosome at the right time during meiosis, so that only Y-chromosome carrying sperms are functional and can successfully fertilize the egg. In this way, the drive carrying males should only produce sons that also carry the molecular scissors on their Y-chromosome. Over multiple generations, females will become rarer and produce fewer offspring; as a result, the population size will fall.

Red fox. Photo by Rylee Isitt licensed under CC BY-SA 2.0.

This “X-shredder” drive has been successfully developed and demonstrated to suppress cage populations of malaria-carrying mosquitos, but has not yet been developed in mammals. The model shows that the X-shredder drive could potentially achieve landscape-scale eradication of mice, rats, rabbits, feral cats, and red foxes, but the probability of success and the time it would take to eradicate them vary greatly.

The researchers investigated the ability of the X-shredder drive to eradicate a population of 200,000 individuals of each species. “CRISPR-based gene drives offer novel solutions for controlling invasive alien species, which could ultimately extend eradication efforts to continental scales,” they concluded.

The method could be effective in small-sized pests, such as rodents and rabbits. The expected time to eradication is 18 years for mice, 19 years for rats, and 48 years for rabbits, with 90% population suppression achieved in around half those times.

However, the results suggest that gene drives are not a one-size-fits-all solution: they might not be so useful in larger species like cats and foxes.

“The probability of eradicating feral cats with gene drives is identical to flipping a coin, 50/50; and provided that the coin lands on the right side, it would take about 140 years to get rid of them,” says Dr. Aysegul Birand, part of the research team. “The probability of eradication is higher for foxes, but the wait is even longer.”

Original source: 

Birand A, Cassey P, Ross JV, Thomas PQ, Prowse TAA (2022) Scalability of genetic biocontrols for eradicating invasive alien mammals. NeoBiota 74: 93-103. https://doi.org/10.3897/neobiota.74.82394

More and more people are becoming aware of the dangers posed by invasive hornets

A study published in the open access journal NeoBiota reveals that citizens and stakeholders are becoming more and more aware of the Asian yellow-legged hornet

Wasps and hornets have a remarkable capacity of surviving transportation and establishing invasive populations in new areas. In some cases, this can generate massive environmental and socio-economic impacts. Such is the case of the Asian yellow-legged hornet (Vespa velutina), which has been spreading throughout Europe and worldwide, threatening to seriously impact beekeeping.

However, research shows that such invasions do not go unnoticed. A team of researchers working on the Asian yellow-legged hornet in Italy (Dr Jacopo Cerri from the University of Primorska, Slovenia, and Dr Simone Lioy, Prof. Marco Porporato and Prof. Sandro Bertolino, from Turin University, Italy) discovered that citizen awareness about invasive hornets is increasing

Asian yellow-legged hornet (Vespa velutina) attacking a colony of honey bees (Apis mellifera) in Italy. Photo by Prof. Marco Porporato

Moreover, they found that the relevant stakeholders – such as beekeepers – are aware of the hornet’s impacts. They consider the Asian yellow-legged hornet as one of the major causes of honey bee decline in Italy, comparing its effects to those of pesticides, and believing it causes more damage than diseases or other native insects.

To evaluate public awareness of this invasive hornet,the researchers adopted an innovative methodology, which they describe in a paper in the open-access journal NeoBiota. In addition to surveying beekeepers, the authors also analysed Internet searches, focusing on Google queries and visits to relevant Wikipedia pages.

Honey bee. Photo by Andy Murray, CC BY-SA 2.0, via Wikimedia Commons

The team found that beekeepers stayed up to date with information on the Asian yellow-legged hornet thanks to a wide range of different channels, such as the Internet, specialized magazines, and activities with other members of their community. Interestingly, they found that conventional media and mailing lists seemed to be of little contribution to knowledge on this species.

With high reproductive potential and no specialized predators, the Asian yellow-legged hornet predates intensively upon the western honey bee, which could decrease pollination, undermine honey production and inflict consequences for the overwinter survival of colonies. It also limits the foraging activity of honey bees by determining a “foraging paralysis”, a state in which honey bees do not leave the colony, fearing its predation. On top of that, as the species builds its nests mainly in or near urban areas, it poses a risk of stings to people, which in some cases could lead to fatalities.

An increased consciousness in citizens and stakeholders will hopefully lead to a higher number of ‘aware eyes’ able to spot invasive hornets in different environments, the researchers explain. Timely reporting of their presence would allow the speedy activation of more appropriate management measures, containing any possible damages before it’s too late.

Research article:       

Cerri J, Lioy S, Porporato M, Bertolino S (2022) Combining surveys and on-line searching volumes to analyze public awareness about invasive alien species: a case study with the invasive Asian yellow-legged hornet (Vespa velutina) in Italy. NeoBiota 73: 177-192. https://doi.org/10.3897/neobiota.73.80359

Pets or threats? Goldfish might be harmful for biodiversity

Goldfish pose a triple threat: not only are they readily available, but they combine insatiable appetites with bold behaviour

Invasive species are one of the leading causes of global biodiversity loss, and the pet trade is responsible for a third of all aquatic invasive species. Pet owners releasing unwanted pets into the wild is a major problem. Whilst many believe this is a humane option, a new research suggests that attempting to ‘save’ the life of a goldfish could in fact lead to catastrophic outcomes for native biodiversity.

To better understand the ecological risks posed by species within the pet trade, the researchers focused on the two most commonly traded fish species in Northern Ireland: goldfish and the white cloud mountain minnow.

Photo by Jeff-o-matic under a CC BY-NC 2.0 license

The globally popular goldfish was first domesticated over a thousand years ago and has since established non-native populations around the world. The white cloud mountain minnow on the other hand is a species with a limited invasion history to date.

This study, published in NeoBiota, developed a new method for assessing the ecological impacts and risks of potential pet trade invaders, based on availability, feeding rates and behaviour. The research showed goldfish to be voracious, consuming much more than the white cloud mountain minnow or native species. In terms of behaviour patterns, goldfish were also found to be much braver, a trait linked with invasive spread.

Dr James Dickey.

Lead author, Dr James Dickey from Queen’s University Belfast, explains: “Our research suggests that goldfish pose a triple threat. Not only are they readily available, but they combine insatiable appetites with bold behaviour. While northern European climates are often a barrier to non-native species surviving in the wild, goldfish are known to be tolerant to such conditions, and could pose a real threat to native biodiversity in rivers and lakes, eating up the resources that other species depend on.

“Our research highlights that goldfish are high risk, but we hope that the methods developed here can be used to assess others in the pet trade across Ireland and further afield. Readily available species are most likely to be released, so limiting the availability of potentially impactful ones, alongside better education of pet owners, is a solution to preventing damaging invaders establishing in the future.”

The research led by Queen’s University Belfast was funded by the Alexander von Humboldt Foundation, Inland Fisheries Ireland and the Department of Agriculture, Environment and Rural Affairs (DAERA) NI. The study was presented at the International Conference on Aquatic Invasive Species in Oostende, Belgium along with a range of other leading research from Queen’s on alien species.

Research article:

Dickey JWE, Arnott G, McGlade CLO, Moore A, Riddell GE, Dick JTA (2022) Threats at home? Assessing the potential ecological impacts and risks of commonly traded pet fishes. NeoBiota 73: 109–136. https://doi.org/10.3897/neobiota.73.80542

Invasive crayfish can cause high fisheries damage

In Zambia and Zimbabwe, a single crayfish may cause annual fishery losses of as much as $6.15

Guest blog post by Josie South

Invasive crayfish have the potential to cause high economic cost to artisanal fisheries in southern Africa through scavenging behaviour and destroying fish fry habitat.

A recent study by C∙I∙B Research Associate Josie South (University of Leeds, UK) with scientists from the South African Institute for Aquatic Biodiversity (SAIAB) quantified the damage caused by two invasive crayfish compared to native crab species, at two temperatures, on tilapia catch and macrophytes.

Redclaw crayfish entangled in a gill net in the Kafue River. Photo by Bruce Ellender

Economic costs of invasive species are vital to prioritise and incentivise management spending to reduce and restrict invasive species. No economic costs have been published for the global invader – the redclaw crayfish (Cherax quadricarinatus), and none for the entire continent of Africa. Another prolifically invasive crayfish, the red swamp crayfish (Procambarus clarkii) is also invasive in various countries of southern Africa. Anecdotal reports of crayfish scavenging from artisanal gillnet fisheries are abundant across the invasive ranges but lacked quantification. Similarly anecdotal information about macrophyte stands being destroyed by crayfish has been reported.

For their study, Josie and colleagues compared the feeding rates per gram of crayfish to that of the native Potamonautid crabs at 19°C and 28°C on simulated fisheries catch and macrophytes to identify how much damage may be caused.

Gill net fish catch damaged by crayfish scavenging. Photo by Josie South

The red swamp crayfish consumed the most macrophytes regardless of temperature, at a higher rate than the redclaw crayfish or crabs. In contrast, redclaw crayfish consumed the most tilapia regardless of temperature, and targeted the tail, abdomen, and fins whereas the crab only consumed the head of the fish. The damage rates of redclaw crayfish were then combined with average mass of crayfish in three invasion cores in Zambia and Zimbabwe. It was found that the damage one crayfish may cause annual fishery losses from $6.15 (Kafue River); $5.42 (Lake Kariba); and $3.62 (Barotse floodplain).

Inland fisheries contribute substantially to the livelihoods and quality of life in Africa. The two invasive crayfish have different capacities for ecological and socio-economic impact depending on the resource and the temperature which means that impact assessments should not be generalised across species.

Redclaw crayfish capacity to damage fish catch was substantial but this should be caveated with two over/under estimation issues: 1) the potential for fisher behavioural change which may reduce crayfish damage and 2) small damage to the fish may render the catch unsaleable and therefore the cost of the whole fish is lost.

Dr Josie South states that while these data are a crucial first step in filling knowledge gaps in crayfish impacts in Africa, it also stresses the need to derive observed costs from fisheries dependent data to avoid misleading estimates.

Also of concern, is the capacity for ecological and socio-economic damage from the red swamp crayfish, which was recently removed from the NEM:BA regulations of prohibited species due to lack of impact evidence.

Read the paper published in NeoBiota

Madzivanzira TC, Weyl OLF, South J (2022) Ecological and potential socioeconomic impacts of two globally-invasive crayfish. NeoBiota 72: 25–43. https://doi.org/10.3897/neobiota.72.71868

This blog post was first published by DSI-NRF Centre for Invasion Biology, Stellenbosch University.

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Invasive alien species? Isn’t there an app for that?

Scientists review 41 invasive species reporting apps and provide recommendations for future development.

Invasive alien species (IAS) are a leading contributor to biodiversity loss, and they cause annual economic damage in the order of hundreds of billions of US dollars in each of many countries around the world. Smartphone apps are one relatively new tool that could help monitor, predict, and ideally prevent their spread. But are they living up to their full potential?

A team of researchers from the University of Montana, the Flathead Lake Biological Station and the University of Georgia River Basin Center tried to answer that in a recent research paper in the open access, peer-reviewed journal NeoBiota. Going through nearly 500 peer-reviewed articles, they identified the key features of the perfect IAS reporting app and then rated all known English-language IAS reporting apps available to North America users against this ideal.

Smartphone apps have the potential to be powerful reporting tools. Citizen scientists the world around have made major contributions to the reporting of biodiversity using apps like iNaturalist and eBird. But apps for reporting invasive species never reached that level of popularity; Howard and his team investigated why.

Smartphone apps like the soon-to-be-released new EDDmapS platform are promising tools for monitoring, predicting, and reducing the spread of invasive species. However, the same explosion of reports has not been realized as that which has been experienced by biodiversity-wide platforms. Howard et al. investigate why there has not been the same boom in use observed for these invasive species-specific apps. Image by Leif Howard and Charles van Rees

User uptake and retention are just as important as collecting data. Howard and colleagues found that apps tend to do a good job with one of these, and rarely with both. In their paper, they emphasize that making apps user-friendly and fun to use, involving games and useful functions like species identification and social media plug-ins is a major missing piece among current apps.

“The greatest advancement in IAS early detection would likely result from app gamification,” they write.

Another feature they would like to see more of is artificial intelligence or machine learning for photo identification, which they believe would greatly enhance species identification and might increase public participation.

The authors also make suggestions for future innovations that could make IAS reporting apps even more effective. Their biggest suggestion is coordination. 

“Currently, most invasive species apps are developed by many separate organizations, leading to duplicated effort and inconsistent implementation”, they say. “The valuable data collected by these apps is also sent to different databases, making it harder for scientists to combine them for useful research.”

A more efficient way to implement these technologies might be providing open-source code and app templates, with which local organizations can make regional apps that contribute data to centralized databases. 

Overall, this research shows how with broader participation, more complete and informative reporting forms, and more consistent and structured data management, IAS reporting apps could make much larger contributions to invasive species management worldwide. This, in turn, could save local, regional, and national economies hundreds of millions or billions of dollars annually, while protecting valuable ecological and agricultural systems for future generations.

Research article:

Howard L, van Rees C, Dahquist Z, Luikart G, Hand B (2022) A review of invasive species reporting apps for citizen science and opportunities for innovation. NeoBiota 71: 165-188. https://doi.org/10.3897/neobiota.71.79597

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Study ranks potentially harmful invasive species in Ghana

Scientists ranked the 110 arthropod and 64 pathogenic species posing the greatest potential threat to the country if established.

A CABI-led study has conducted a comprehensive survey of nearly 200 potentially harmful alien plant species that could have a detrimental impact upon agriculture, forestry and biodiversity in Ghana once they enter the country.

Invasive Alien Species (IAS) continue to shape the global landscape through their effects on biological diversity and agricultural productivity. The effects are particularly pronounced in Sub-Saharan Africa, which has seen the arrival of many IAS in recent years. This has been attributed to porous borders, weak cross border biosecurity, and inadequate capacity to limit or stop invasions.

A farmer shows cassava root affected by cassava brown streak virus alongside a healthy root in a country where the disease is present – one of the 64 pathogens assessed by the scientists. Credit: CABI

The research, the findings of which are published in the journal NeoBiota, ranks 110 arthropod and 64 pathogenic species that pose the greatest threat but are not yet officially present in the country. However, they could arrive as ‘stowaways’ in cargo from other countries around the world, the scientists believe.

Dr Marc Kenis, Head Risk Analysis and Invasion Ecology at CABI, led on the horizon scanning exercise supported by colleagues from a range of institutions including Ghana’s Plant Protection and Regulatory Services Directorate (PPRSD).

Among the top arthropods prioritised by Dr Kenis and his team were the pink hibiscus mealybug (Maconellicoccus hirsutus Green) and melon thrips (Thrips palmi Karny) while the top pathogens highlighted include cassava brown streak virus and Maize lethal necrosis disease.

Cassava in Ghana, for example, is a main staple crop and contributes about 22% and 30% to the Agricultural Gross Domestic Product (AGDP) and daily calories intake respectively. The crop, however, can be at risk from cassava brown streak virus which can reduce yields by up to 70%.

Maize lethal necrosis disease, on the other hand for instance, can be a major disruptor of maize crops in Ghana where maize accounts for more than 50% of the country’s total cereal production. The disease can cause losses of between 50-90% depending on the variety of maize and the growing conditions of the year.

The scientists also found other species recorded in Africa that included 19 arthropod and 46 pathogenic species which were already recorded in the neighbouring countries of Burkina Faso, Côte d’Ivoire, and Togo.

Dr Kenis, who is based at CABI’s centre in Switzerland, said, “The ultimate objective of this research was to enable prioritization of actions including pest risk analysis, prevention, surveillance and contingency plans. Prioritisation was carried out using an adapted version of horizon scanning and consensus methods developed for ranking IAS worldwide.

“We have demonstrated that through horizon scanning, a country can identify potential invasive plant pests, both invertebrates and pathogens, and use the information to determine the risk associated with each.

“This will enable the country to invest the limited resources in priority actions such as preventing arrival and establishment of IAS, Pest Risk Analysis (PRA), surveillance and developing contingency plans.

“This study can serve as a model for future projects on plant pests’ prioritisation in Africa and elsewhere. It would be applicable for assessing the risk of invasive plant pests in any country or region, e.g. trade blocks, with minor modifications of the method, particularly in the mini-PRA protocol used to score species.”

The full lists of arthropod and pathogenic species surveyed can be found within the full paper which can be read online.

Mr Prudence Attipoe, Deputy Director Head Plant Quarantine Division, PPRSD, said, “The horizon scanning exercise for Ghana would give the PPRSD an insight into invasive pests which could possibly enter the Nation. The tool is timely and appropriate for conducting PRA for planning, training and future preparedness. The success of this exercise would pre-empt the introduction of these invasive pests into the country in order to protect Ghana’s agriculture, forestry and also cause staff of PPRSD to be more vigilant at the borders for these pests.”

Research paper:

Kenis M, Agboyi LK, Adu-Acheampong R, Ansong M, Arthur S, Attipoe PT, Baba A-SM, Beseh P, Clottey VA, Combey R, Dzomeku I, Eddy-Doh MA, Fening KO, Frimpong-Anin K, Hevi W, Lekete-Lawson E, Nboyine JA, Ohene-Mensah G, Oppong-Mensah B, Nuamah HSA, van der Puije G, Mulema J (2022) Horizon scanning for prioritising invasive alien species with potential to threaten agriculture and biodiversity in Ghana. NeoBiota 71: 129 148. https://doi.org/10.3897/neobiota.71.72577

How to get people interested in invasive species?

While blacklists are an effective tool for preventing and managing new biological invasions, they don’t always raise public awareness of invasive alien species, a new study published in the open-access journal NeoBiota found. Important policy-making initiatives do not necessarily raise public awareness about biological invasions, and efforts should be more focused on supporting policy-making with well-planned communication campaigns, the research concludes.

Catchy news and viral videos work best to attract public attention to invasive alien species

Blacklists are one of the most common policy measures to limit biological invasions. They identify small groups of highly impactful invasive alien species: species introduced outside their native range that threaten biodiversity. By doing so, they inform key decision-makers, who then impose limitations or bans on their trade and introduction, or set requirements about specific actions to manage already established populations.

While they have been found to be effective at preventing and managing new biological invasions, we don’t know if blacklists actually raise public awareness of invasive alien species. In principle, they could do so, as they might attain a certain echo in the media and provide the general public with notorious examples of invasive alien species.

Coypu. Photo by Aurelio Perrone

In 2016, the European Union published the List of Invasive Alien Species of Union concern, which contains species that are banned from import, trade, and release in Europe. It had a certain echo in the media, and having come at a time where Internet searches are so pervasive that they can be used to measure public attention,  the Union List made a good case study for exploring blacklist impact on public awareness.

A research study, coordinated by Jacopo Cerri from the University of Primorska, Slovenia, and Sandro Bertolino from the University of Turin, Italy, explored if the publication of the Union List increased visits of the  Italian Wikipedia pages about invasive alien mammals, many of which were included in the list. Wikipedia is the largest online encyclopedia and a major source of information for motivated Internet users who go beyond search engines such as Google. As a comparison, the researchers used visits to Wikipedia pages about native mammals in Italy, and adopted a causal impact analysis to quantify differences.

The study found no effect of the publication of the Union lists over visits to Italian Wikipedia pages of invasive alien mammals, compared to pages about native mammals. After 2016, there were single peaks of visits to pages of some of the species, probably caused by viral videos and news about large-scale control initiatives or mass escapes from captivity. In one instance, peaks in visits aligned with news about the coypu – at the time, several national media outlets ran stories addressing the concerns of public administrations regarding the rodent’s impact on the stability of river banks. Similarly, a peak observed between late 2018 and February 2019 was likely caused by news about the release of 4,000 minks from a fur factory in Northern Italy, which attracted considerable attention in the national and regional media.

These attention peaks, however, did not last in time and don’t reflect a systematic change in public awareness about invasive alien species.

“Overall, our findings indicate that blacklists, despite having the potential to raise public awareness towards biological invasions, might fail to do so in practice,” the researchers conclude.

“Agencies who want to achieve this goal should rather develop tailored communication campaigns, or leverage on sensational news published in the media.”
 

Research article:

Cerri J, Carnevali L, Monaco A, Genovesi P, Bertolino S (2022) Blacklists do not necessarily make people curious about invasive alien species. A case study with Bayesian structural time series and Wikipedia searches about invasive mammals in Italy. NeoBiota 71: 113-128. https://doi.org/10.3897/neobiota.71.69422

Unwelcome guests: International tourism and travel can be a pathway for introducing invasive species

International tourism can facilitate the dispersal of exotic species. A new analysis of data from tourism accommodations and exotic organism detections in New Zealand, published in NeoBiota, shows that levels of detection significantly correlated to international and domestic tourist movement, even with population levels taken into account. There was no detectable difference between the risk from international and domestic tourists, indicating that tourism as an activity correlates with the introduction and spread of exotic species.

Tourists, albeit unwittingly, may help such unwanted organisms spread further and conquer new lands – they can carry them over in their luggage or on their clothes and shoes. In 2011, a study from New Zealand found that, for every gram of soil on the footwear of aircraft passengers arriving from abroad, there were 2.5 plant seeds, 41 roundworms, 0.004 insects and mites, and many microorganisms, such as fungi that could cause plant diseases. Moreover, these organisms were alive, and some of them were known to be biosecurity threats. Importantly, tourism can introduce risk in two directions, namely from the arrival of international travellers and also the return of residents from international travel.

An important question, then, is to what degree they play a role in the spread of exotic organisms. A study, carried out by Dr Andrew Robinson of the Centre of Excellence for Biosecurity Risk Analysis at the University of Melbourne and Mark McNeill of AgResearch New Zealand, looks to answer that question.

To do so, the researchers compared data on the interceptions of exotic organisms in New Zealand against accommodation data for international and domestic tourists, factoring for the country’s population distribution. The study, recently published in the open-access journal NeoBiota, covered the period between 2011 and 2017, and the exotic organisms that were detected included insects, spiders, mites, snails, plants, and roundworms. 

Robinson and McNeill found a significant relationship between levels of incursion detection and tourism accommodation records: the number of nights spent in hotels significantly correlated to the detection of exotic pests for that period. Importantly, the study found no significant difference between the effect of international and domestic tourism, proving that even travel within the country can facilitate the spread of exotic species. A significant positive correlation was also found between the detection of exotic organisms and population numbers across different regions. 

“The core take-home message is that within-country tourism movements are significantly correlated to the detection of exotic pests,” the researchers explained. That is, tourists and returning residents bring bugs in, and both are implicated at spreading them once they are in the country. They suggest that biosecurity authorities should continue allocating resources to the management of invasive species and pests that get carried around by tourists and their activities. 

However, they also point to the biosecurity risk posed by other possible pathways for of exotic organisms, such as sea freight. A comparison between the different ways of introduction and dispersal would provide a better understanding of relative risk, they conclude.

Research article:

Robinson AP, McNeill MR (2022) Biosecurity and post-arrival pathways in New Zealand: relating alien organism detections to tourism indicators. NeoBiota 71: 51-69. https://doi.org/10.3897/neobiota.71.64618