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Goal: Apply Knowledge Globally Hitchhiking seeds pose risk of plant invasions at seaports-of-entry

Rima Lucardi (left) finished vacuuming an air-intake grille and was placing a specimen bag into the day’s collections being held by SCBPAS Milton A. King (USCBP, right) on one of the 4-story “container racks” at the GCT. Viable seeds were collected from these grilles associated with refrigerated shipping containers. (Forest Service photo by Chelsea Cunard)


Hitchhiking seeds collected from refrigerated shipping containers can be viable and pose a significant invasion risk, according to recent research at the Port of Savannah. Seaports-of-entry, where commodities arrive in the U.S. from overseas via sea transportation, are hotspots of nonnative plant diversity and are significantly different from nearby sites. Biological invasions by nonnative organisms have been repeatedly shown to detrimentally impact the environment and the economy of the nation.


More than 90% of global trade commodities are transported by huge cargo ships on the Earth’s oceans. Seaports are the initial point-of-entry for imported commodities including timber and food. Commodities that need to be kept cool are transported in air-tight refrigerated shipping containers. They are built with climate controls and a condenser system that includes air-intake grilles. As these grilles take in air, they create a vacuum that can suck up plant seeds, insects, and other debris at the farm or port-of-origin, from the ocean, or at seaport stops along the way.

Biological invasions by nonnative organisms have been repeatedly shown to detrimentally impact the environment and the economy of the nation. Propagule pressure is the number of individuals and the frequency of entry and is considered the greatest predictor of invasion success. SRS researchers partnered with the U.S. Customs & Border Protection, Agriculture Program (Dept. of Homeland Security), other state and federal agencies, and the Georgia Ports Authority at the Port of Savannah to examine if the vascular plant community on-site differed greatly from nearby sites due to constant propagule pressure of escaping nonnative seeds, continual heavy-equipment disturbance, and the constant hum of human activity.

The team collected debris, including seeds, from the air-intake grilles of refrigerated shipping containers to measure plant propagule pressure and the risk of plant invasions by nonnative species. The study found that the greenspaces on-site at the Garden City Terminal, the Port of Savannah’s container-handling facility, were significantly different from other local plant inventories, with significantly higher numbers of nonnative plant species present. From the debris vacuumed from refrigerated shipping containers, four monocot species were found to pose the greatest risk of establishment at the Garden City Terminal, even with extremely low escape rates. The collected seeds were viable, though viability rates varied.

Principal Investigator
Rima D. Lucardi, PhD, Research Ecologist
4552 - Insects, Diseases, and Invasive Plants
Strategic Program Area
Invasive Species
An initial industrial flora: A framework for botanical research in cooperation with industry for biodiversity conservation
CompassLive Articles
Hitchhiking Seeds Pose Substantial Risk of Nonnative Plant Invasions
Inventorying an ‘Industrial Flora’
External Partners
Travis D. Marsico - Arkansas State University
Chelsea E. Cunard - Arkansas State University
Emily S. Bellis - Arkansas State University
Jarron K. Gravesande - Arkansas State University
Kevin S. Burgess - Columbus State University
Samantha J. Worthy - Columbus State University
Lauren E. Whitehurst - Columbus State University
Steven C. Hughes - University of Georgia Herbarium