Molnar, J., Gamboa, R. Revenga, C, and Spalding, M.D. 2008 Assessing the global threat of invasive species to marine biodiversity. Frontiers in Ecology and the Environment, Vol 6, No. 9. pp. 485- 492.

It is widely accepted that invasive species are threatening to marine and terrestrial ecosystems and biodiversity. The impacts of these species have not been quantitatively assessed on a global level. In this report, over 350 databases and other sources are used to synthesize information on 329 marine invasive species. This included distribution, impacts on biodiversity, and introduction pathways. International shipping as well as aquaculture are two of the major ways that invasive species are introduced into an ecosystem.

The topic of this study is marine invasive species worldwide. There are multiple research questions being asked. One of them is, how do we quantify geographic distribution and pathways of invasive species? What are the invasive species by ecoregion and how threatening are they to the region?

An ecoregion is an area of relatively homogeneous species composition, quite clearly distinct from adjacent systems. They used this unit of analysis because it is global in scale and useful for ecological guides.  The database development was done by collecting data from a variety of sources and compiling the information into a geographically referenced database. Detailed information was collected about the threats that each invasive species posed on the biodiversity using a scoring system. Each invasive species was assigned a score from the following categories: ecological impact, geographic extent, invasive potential, and management difficulty. This score was assigned globally for each species. The pathway analysis is based off of the US National Invasive Species Council’s Pathways Team. It allows documentation of all known and likely pathways for each species in the database. The creation of the database was by using expert knowledge and published works. From there the analysis was done through the database and many different statistical tests were able to be run and averages analyzed.

The database includes 329 marine invasive species in 194 ecoregions. The data shows high levels of invasion in Northern California in San Francisco (n= 85 species, 66% which are harmful). The most common pathway is shipping and transfer through ballast water. Using data collected in this assessment, global patterns can be identified in hopes to conserve and create policy effort to decrease the number of invasive species through out the world. It was found that there is under reporting of both microorganisms and low impact invasive species on the global scale.