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Hitchhiking Seeds Pose Risk of Plant Invasions at Seaports

Dr. Rima Lucardi (left) 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. Viable seeds were collected from these grilles associated with refrigerated shipping containers.
Hitchhiking seeds collected from refrigerated shipping containers can pose a significant invasive species risk, according to recent USDA Forest Service 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.
Fiscal Year
Research Station
Research Unit(s)
Insects, Diseases, and Invasive Plants
Principal Investigator(s)
More than 90% of global trade commodities are transported by huge cargo ships. 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 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 can detrimentally impact the environment and the economy of the nation. USDA Forest Service 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 plant community on-site differed greatly from nearby sites due to escaping nonnative seeds and continual heavy-equipment disturbance. The team collected debris, including seeds, from the air-intake grilles of refrigerated shipping containers and 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.
Forest Service Partners
External Partners
  • Dr. Travis D. Marsico, Dr. Chelsea E. Cunard, Dr. Emily S. Bellis, Jarron K. Gravesande - Arkansas State University
  • Dr. Kevin S. Burgess, Samantha J. Worthy (Past Graduate Student, now PhD student at Univ. of Maryland) and Lauren E. Whitehurst (Past Graduate Student, now PhD student at Univ. of Florida) - Columbus State University
  • Steven C. Hughes - University of Georgia Herbarium
  • Chip Bates, Chris Barnes, Billy Brown - Georgia Forestry Commission
  • Milton A. King, Rebecca Y. Rhinehart - US Customs & Border Protection
  • Gordon Hammer (retired) and Client Relations Center staff - Georgia Ports Authority