Assessing the Global Threat of Invasive Species to Marine Biodiversity

Molnar, J. L.,Gamboa, R. L., Revenga, C., and Spalding, M.D. (2018). Assessing the global threat of invasive species to marine biodiversity. Frontiers in Ecology and the Environment 6, no. 9: 485–492. PDF

Summary

Before we can understand which marine invasive species might be a threat to the Northeastern United States, we first need to have a list of all marine invasive species. Molnar et al. (2008) compiled a list of 329 marine invasive species from hundreds of sources around the globe to get a big-picture perspective on which marine species are most invasive, how these species relocate to new environments, how severe their effects are on invaded ecosystems, and how they can best be managed.

They determined the introduction pathway for each species, and also scored each species from 1 (least severe) to 4 (most severe) in four main categories: Ecological impact, geographic extent, invasive potential, and management difficulty. The resulting dataset is publicly available online here.

Take home points

  • The most invaded marine regions in the world are the West Coast of the United States, the area surrounding Hawaii, the North Sea (east of Great Britain), and the Levantine Sea (eastern end of the Mediterranean Sea).

  • Marine invasive species are most commonly crustaceans, mollusks, or algae.

  • Shipping and aquaculture are the two most common pathways for marine invasive species to be introduced to a new environment.

Management implications

  • Managing marine invasives is best done proactively. Once an invasive species has established, it is very difficult, expensive, and sometimes impossible to eradicate. Therefore, managers can use this database to identify which marine invaders may expand into Northeastern waters as they warm due to climate change.

  • Policies should focus on regulating the two dominant introduction pathways: shipping and aquaculture. Policymakers should coordinate across national and ecological boundaries, as existing local restrictions are ineffective.

  • When deciding whether to allow an intentional introduction of a marine species, include both ecological and economic risks. Economic risks are often overlooked.

Keywords

Novel introduction pathways; Management efficacy; Impact studies; Invasive marine species; Global distributions