Trade Routes Explain Invasive Species

New research uncovers the influence trade routes have on the spread of invasive species to regions near and far away.

In the age of globalization, the spread of invasive species around the world is a serious problem. The consequences include but are not limited to displacement of species and extinction of native flora and fauna. In many cases, pathways by which invasive species travel can be traced by looking at trade routes.

For example, two rats hop on a ship in the U.S. and hop off on a remote island. Soon the island species are threatened by a predator they have never encountered before. This is a common pathway for invasive species, but can such a big problem really have such a simple explanation?

island conservation invasive species threaten ricords iguana

The Ricord’s Iguana is threatened by feral cats on Cabritos Island, Dominican Republic. Credit: Island Conservation

Researchers suspected there might be more to the story of how these species are transported around the world; since most trade occurs regionally, this does not alone explain the distribution pattern. Scientists from Germany and Austria recently published a study which examined the spread of 1,380 known invasive species and compared them to trade flow around the world. Dr. Hanno Seebens of the Senckenberg Biodiversity and Climate Research Center explained:

A clear pattern is apparent. A particularly large number of species originates in areas that are located at a distance of approximately 10,000 kilometers from the place of introduction. Contrary to this, the majority of the imported goods come from the immediate neighboring countries.

To study invasive species pathways, the researchers developed a computer model that analyzed trade flows in conjunction with the distribution of invasive species around the world.  What they found caught them by surprise.

First, species are often transported regionally in short distances of up to 3,000 kilometers. These species are often originally within their native ecosystem but get moved around by these shorter trade routes. Second, researchers found that when species are moved significant distances to regions where they establish invasive, they can then be transported along short trade routes, thereby expanding the invaded region.

island conservation antipodean wandering albatross

Seabirds like this Antipodean Wandering Albatross may not successfully breed in the presence of invasive predators. Credit: Jason Zito/Island Conservation

The study showed that mammals, reptiles, and fish are more likely to be transported short distances while plants and birds are more capable of long-distance invasion. Dr. Bernd Blasius of the Institute for Marine Chemistry and Biology (ICBM) at the University of Oldenburg commented:

The spread of non-native species is a complex process, and the data situation is far from complete. Therefore, it is even more astonishing that the spread can be explained with simple models…This gives us reason to hope that in the future, the introduction of exotic species can be better understood and more efficiently contained with the aid of such models.

Understanding how organisms become invasive is an important step in preventing their proliferation. The study suggests that techniques such as increasing monitoring in regions near sensitive habitat and increasing biosecurity along trade routes are important measures for safeguarding ecosystems against invasive species.


About Emily Heber

Emily is a recent graduate from UC Santa Barbara with a BS in Zoology. As a student, she discovered that she had a passion for the conservation of endangered species and their ecosystems. Her background in informal education has allowed her the opportunity to share her passion for animals with others, something she seeks to continue doing while working with the communication team. In her spare time, Emily enjoys exploring the amazing hiking trails found in Santa Cruz and tries to SCUBA dive whenever possible. Emily is excited to join the Island Conservation team and to help share the amazing work that is being done here.

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