Policy and research challenges for managing species invasions

Species invasions can occur through multiple types of pathways, and the challenge of controlling alien species lies not only in identifying the invasion pathway, but also linking that pathway to management decisions. In his recent paper in Journal of Applied Ecology, Philip Hulme outlines the framework lately adopted by the Parties to the Convention on Biological Diversity to identify, prioritize, and manage invasion pathways. He identifies six types of invasion pathway, and highlights the policy and scientific challenges still remaining in order to meet target goals for controlling invasions:

1. Release. Alien species are deliberately released for purposes such as biological control, hunting, or ecosystem services. Assisted colonization is a form of deliberate release, and carries risks of unintended consequences with insufficient pre-assessment. It is critical to understand what the risk of invasion may be in assisted colonization, and require those responsible for introducing new species to retain responsibility for negative consequences.
2. Escape. Captive species can accidentally or deliberately get into the wild and expand. Regulating the captive species trade is difficult due to the large number of legal wild pets, the expansive illegal trade in prohibited species, and public resistance to restricting the pet trade. Creating a whitelist of acceptable species would shift the burden of proof to traders rather than the public.
3. Contaminants. Pathogens, parasites, insect pests, and seeds can all be transported unknowingly in commercial commodities, including wild pets. Efforts should be increased to inspect “live” commodities that are globally transported, and to more closely monitor new outbreaks.
4. Stowaways. Alien species unintentionally travel on transport vessels, notably shipping containers and increasingly on tourist clothing, footwear and equipment. Invasions may be better managed by increasing inspection at borders of high-risk passengers and their luggage, even though such measures may be unpopular.
5. Corridors. Human infrastructures such as tunnels, interbasin water transfers, and especially canals can facilitate biological invasions. Economic benefits, indirect consequences and unclear invasion mechanisms all contribute to these types of corridors being largely ignored. Scientists need to better articulate how infrastructure corridors can assist invasions, and address how the consequences of invasion compare to the potential economic and cultural benefits of building them.
6. Unaided. Some species are excellent dispersers and invade without any assistance. Although it may be difficult to prevent unaided invasion, countries adjacent to an invaded region may benefit from coordinated regulations to prevent further invasion, with negative consequences for those governments that fail to do so. Transboundary invasion highlights the potential for international collaboration in addressing a global environmental issue.