Globalisation accelerates alien species’ introduction The impact of IAS takes different forms. Competition for habitat and resources, predation on native species, transmission of disease (to humans and to other species), destruction of habitats or infrastructure, and hybridisation (mating with native species can alter the gene pool and genetic diversity) are among the negative affects of invasive species. Species have always moved from one place to another, but the difference is that today globalisation has greatly accelerated the process whereby animals and plants leave their origins and arrive at destinations where, if conditions are favourable, they will try and settle. Reversing globalisation is neither desirable nor practical for various reasons. Current trends suggest it will increase over the next years leading most likely to an uptick in the rate of arrival of IAS caused deliberately or unintentionally. In addition, climate change may hasten the arrival of IAS by creating conditions in hitherto inhospitable areas in which alien species can survive and even thrive. These two factors, climate change and globalisation, have contributed to an increase in the volumes of species that are carried from one part of the world to another multiplying the number of introductions and greatly increasing the likelihood of successful colonisation by an alien species.
Ports are a common gateway for invading species
Given these factors, tackling IAS calls for a raft of measures including early detection and rapid response, more rigorous implementation of existing legislation such as the ballast water directive, and the creation of information and awareness about the threats represented by IAS. At the University of Oviedo in Asturias in the north west of Spain, a team of researchers is studying the issue. In December last year they organised the BluePorts 2019 workshop which brought together port stakeholders, researchers, managers, teachers, students and citizens to discuss biologically safe or “blue” ports, that have adequate facilities for the reception of ballast water and the treatment of fouling, the two principle ways for the introduction of alien species through ports. The objective of the conference was to work with the maritime community to create relevant blue port services and thereby prevent discharges at sea.
Another, older, initiatives the researchers took was to organise the international Alertools workshop in 2016. Prof. Yaisel Borrell (Biology) and Prof. Eduardo Dopico (Education Sciences) coordinated the workshop under the scientific direction of Prof. Eva Garcia-Vazquez. The workshop not only discussed technical subjects such as sensors for the early detection of invasions and molecular methods for detecting nonindigenous individuals, but also included a session on educational and citizen science approaches to increase awareness about biological invasions, and using citizen patrols to monitor the appearance of alien species. Of all the threats to biodiversity, invasive species are one of the main challenges, says Prof. Borrell, but people are unaware of it. It is therefore critical to educate the general public as a way of developing a kind of early warning system, as once an invasive species is established it is almost impossible to do something about it. Besides, we work at a publicly funded university and have a moral obligation to inform the public, so outreach, education and dissemination are a regular part of our activities. Prof. Dopico and his colleagues organised therefore a series of public talks in schools in the city of Gijon about the problems of biological invasion. Divers, fishers, people running or strolling on beaches, students and other ordinary citizens can alert the authorities or the scientific community if they detect something that might be an alien species. But for that they need to be educated to recognise something unusual.
Early detection and eradication are critical to prevent spreading
The more information that is available about an invasive species— its origins, population structure, genetic diversity, and expansion trends—the more can be done to prevent it from colonising a space and to eradicate it in case it does spread. In 2014 Prof. Borrell and Prof. García-Vazquez observed for the first time the New Zealand pygmy mussel (Xenostrobus securis) in the Avilés estuary in the Bay of Biscay in one port and at low density. A year later the researchers found that the species had rapidly and successfully spread possibly encouraged by new arrivals from the harbour as the port receives over 1,000 vessels (commercial, naval, recreational, and fishing) in a year. In a paper based on this study(1) the authors suggest that the mussel arrived through ballast water or macrofouling and its spread to other regions could be prevented by monitoring the ballast water of outbound ships. In another paper(2) Laura Miralles and her colleagues documented how this population of pygmy mussels that had spread in the estuary could be controlled. The researchers used an environmental DNA-based tool developed in the earlier study to detect the presence of the mussel and deployed enthusiastic volunteers to manually remove the invaders. The study revealed the importance of early detection and removal in preventing colonisation of the estuary by the mussel. It also showed the usefulness of the eDNA tool to identify the presence of the mussels, and the significance of volunteers and citizen scientists in efforts to eradicate the pest. Periodic drives to manually remove the invader would be among the recommendations in a strategy to manage it.
These and other studies by these scientists have shown that invasive species can colonise spaces more easily when the environment of the area has been degraded by human activity, such as at a port, for example. The lack of predators, the ability of the invader to reproduce easily, and its tolerance of environmental changes all contribute to its success, if it manages to settle. Areas with high levels of conservation and tend not to have niches that an invading species can occupy and are thus more resistant to invasion. Monitoring marine traffic at a port could also provide an estimate of the port’s vulnerability to invasion, says Prof. Borrell. It would mean first identifying the species that are already present in the port and then analysing the traffic to identify potential threats. If the port has never been surveyed before then a species found by the sampling would be considered invasive if it is invasive in other parts of Europe or if it originates from a remote place such as the New Zealand pygmy mussel. If vessels arrive from other parts of Europe with similar environmental conditions that are already suffering from invasive alien species, then the risk that they arrive at the port is high. Armed with this information it will be possible to take steps to detect and prevent the invaders from settling. For example, by developing techniques for the early detection of that species.
Alien species are sometimes introduced intentionally
While ballast water is one vector for the arrival of exotic species, deliberate introduction by humans is another way for alien species to reach a new environment. The Pacific oyster (Crassostrea gigas), Japanese clam (Ruditapes philippinarum), some exotic seaweeds from Japan and Korea, and even such widely distributed species as rainbow trout (Oncorhynchus mykiss) and catfish (Silurus glanis) are all introduced. Many of these species were introduced for their potential to be farmed, and their impact on the wider environment was ignored. For a species to be termed invasive it must be able to reproduce in the new area and grow in size and numbers to displace or harm native species or damage the habitat, says Alba Ardura, a former Université de Perpignan postdoctoral researcher now working at the University of Oviedo. Spain maintains an official list of invasive species that declares these may not be cultivated, sold, or transported from one place to another. For a species of commercial value, being included on the list would completely depreciate this value. Economic interests that profit from this species will therefore fight to prevent it from being included on the list. Many people live directly or indirectly from rainbow trout, catfish, and Pacific oysters so policy makers have to balance the different interests. This balance can shift depending on the ideology of the government in power and the constituencies it depends on for its votes. As scientists we can identify the problem and its consequences and inform the decision-makers (and the public), says Prof. Borrell, and then the decision is up to them.
Given the increase in IAS what can be done to slow their spread? One way, says Prof. Garcia-Vasquez, is to be more particular about the small things—applying antifouling paint to ships’ hulls, cleaning fishing gear more carefully, preventing the destruction of habitats and diversity when carrying out human activities, applying the regulations on ballast water, and preventing marine litter as it provides a substrate to which animals can attach themselves and then be carried long distances. When it comes to invasive species, prevention is cheaper and easier than cure. In fact, once the alien species has established itself a cure may not be possible at all.
(1) Devloo-Delva, Floriaan & Miralles, Laura & Ardura, Alba & Borrell Pichs, Yaisel & Pejovic, Ivana & Tsartsianidou, Valentina & Garcia-Vazquez, Eva. (2016). Detection and characterisation of the biopollutant Xenostrobus securis (Lamarck 1819) Asturian population from DNA Barcoding and eBarcoding. Marine Pollution Bulletin. 105. 10.1016/j.marpolbul.2016.03.008.
(2) Miralles, Laura & Dopico, Eduardo & Devloo-Delva, Floriaan & Garcia-Vazquez, Eva. (2016). Controlling populations of invasive pygmy mussel (Xenostrobus securis) through citizen science and environmental DNA. Marine Pollution Bulletin. 110. 10.1016/j.marpolbul.2016.06.072.