Strategies to manage invasive alien species

A recent report by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) highlighted that invasive alien species (IAS) pose major global threats to nature, economies, food security and human health. These results are surprising to few as it is well known that ‘invasive alien species cause dramatic and, in some cases, irreversible changes to biodiversity and ecosystems, resulting in adverse and complex outcomes across all regions of Earth, including local and global species extinctions’, as was stated in the assessment (IPBES 2023, 4). With IAS as one of the five major direct drivers of biodiversity loss globally, alongside land-use and sea-use change, direct exploitation of organisms, climate change, and pollution, people need to approach IAS management from various angles.

The spread of IAS is primarily driven by intentional and unintentional human activities due to globalization. Going back over 20 years, it was recognized that simple activities like shipping car tires from one country to another has transported invasive alien mosquito species like Aedes albopictus and Aedes aegyptii which have brought with them diseases such as malaria, Zika and West Nile fever. The examples of species moved from one area to another, whether intentionally or unintentionally, by humans is massive at >37,000 species (IPBES 2023). Of those, more than 3500 of the alien species introduced by human activities pose major global threats to nature, economy, food security and human health, according to the IPBES report (2023). Those 3500 IAS also play a key role in 60% of global plant and animal extinctions, and cost humanity more than $400 billion a year (IPBES 2023).

The IPBES report is massive and brings together a huge body of evidence that can be used by governments, organizations and even individuals to manage IAS. As Prof. Pauchard, co-chair of the assessment, stated, ‘The good news is that, for almost every context and situation, there are management tools, governance options and targeted actions that really work’ (IPBES 2023). The report recognizes that while eradication of an IAS is the most effective way to reduce its spread, it just isn’t realistic in all cases, and while effective management can reduce the severity of invasions or even eradicate the invaders, with human globalization activities, invasions will likely be a recurring issue.

Understanding that invasions are likely to continue, prevention is still one of the best approaches to IAS management. There are now 196 countries with national IAS checklists who intend to prevent the entry of IAS; however, 83% of these countries are lacking national legislation or regulations on IAS (IPBES 2023). Without federal rules and with numerous countries lacking in border biosecurity measures, it is difficult to limit the flow of biological species from one area to another. In addition, aquatic species can be very hard to exclude as they may stow away in ship ballast water. That ballast water may include bacteria, microbes, small invertebrates, eggs, cysts and larvae of various species, and while many countries have accepted international conventions on ballast water since 2004, there are still countries developing domestic ballast water policies which will help to stop the unintentional movement of species from one area to another.

A management mechanism that policy creators have found effective is IAS risk assessment. Target 6 of the recently adopted Kunming-Montreal Global Biodiversity Framework suggests that we ‘eliminate, minimize, reduce and or mitigate the impacts of invasive alien species on biodiversity and ecosystem services’ (CBD 2022, 9). To determine which of those aforementioned approaches should be employed, a comprehensive risk assessment relating to the species that will be affected by the IAS may be employed. Risk level can then be used to prioritize and develop rapid responses when required. In some nations, such as Great Britain, a non-native species risk analysis mechanism has existed since 2006. Within this mechanism risk assessments on IAS are carried out by independent experts, peer reviewers and a panel of risk analysis experts. This comprehensive approach has enabled the UK to appropriately react to IAS.

The UK has another secret weapon in fighting invasives and that is their massive army of ‘backyard biologists’ or ‘citizen scientists’, as these individuals are educated in what species are invasive and can help to detect and identify IAS early in their invasion. The IPBES IAS report noted that ‘Public awareness, commitment and engagement and capacity-building are crucial for the prevention and control of invasive alien species’ (IPBES 2023, 8). Engaging people globally can help with early IAS identification and documenting invasions by collecting data, identifying and removing IAS, and employing measures to reduce the spread of IAS and create conditions that are more optimal for native species. The early identification of a species is often the difference between eradication and control. In terms of cost, early eradication is vastly cheaper, and by educating populations everyone can become part of the solution.

With the increased movement of people and goods brought about by globalization, environmental degradation and climate change, the number of IAS and their impacts are projected to increase in the future. It would be incredibly costly to attempt to eradicate all IAS from foreign lands, but there are some cases where the cost of management pales in comparison to the benefit. Therefore, a cost–benefit analysis may support policymakers and management teams to make decisions regarding where to allocate funding. One example of where a cost–benefit analysis was completed and spending was allocated is for management of the Mediterranean fruit fly, whereby sterile males are released, ultimately decreasing the population and saving fruit worth significantly more than the management effort. Using a business approach also helps governments and organizations to plan and earmark funds for the IAS management effort in cases where eradication is just not possible.

The IPBES report has comprehensive information on the 3500 species identified as ‘invasive aliens’ and is meant to be a resource for those who are faced with an IAS invasion. Once these species are in a new environment there are essentially three approaches: (1) try to eradicate the invaders, (2) contain the IAS and stop their spread, or (3) allow the invasion to occur. Should governments decide to allow invasions to occur, my hope is that they will manage the IAS in a way that promotes biodiversity and allows for native and non-native species to co-exist.

In summary, if the IPBES IAS authors were asked if IAS can be managed, their answer would be a resounding yes. With all of the strategies identified in their report it is clear that there are cost-effective ways to combat this problem, which include: regulations and border control, education, engagement of big business, international co-operation and, most importantly, the involvement of as many knowledgeable people as possible. Integrated approaches to manage IAS are highlighted in the IPBES Invasive Alien Species report (2023). The report is publicly available at www.ipbes.net.

Disclosure statement

No potential conflict of interest was reported by the author.

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Rebecca Trueman

Rebecca Trueman, as managing editor for Biodiversity, consults with various partners to develop news stories for biodiversity. This story was produced after interviewing Sue Nichols, Assistant Director and Research Communication Strategist, Center for Systems Integration and Sustainability, Department of Fisheries and Wildlife, Michigan State University.