To identify the most threatened areas, Colunga-Garcia and colleagues selected 39 invasive plant pests reported by the North American Plant Protection Organization or the Cooperative Agriculture Plant Survey as being of U.S. economic importance. They then compiled a list of all U.S. county occurrences for each selected group of pests through July 2009. They found one or more of the 39 selected pests in 504 counties in 36 out of 48 states; 357 counties harbored just one pest, and 147 counties had two or more. Additionally, the coastal states seemed to be at greatest risk for invasion with at least one pest occurring in each.
"Major coastal urban areas, for instance, should be carefully monitored since they hold a double threat of invasion: a populous area receiving large volumes of potentially infested imports," says Colunga-Garcia. "These characteristics can lead to the rapid spread of plant pests, starting in the urban end of the gradient and moving outward to rural areas as people transport infested materials for development or recreation."
Humans are a driving factor in the spread of exotic plant pests, not just from importing plants and their associated hitchhikers directly to the ports, but likely dispersing pests inadvertently into exurban areas as well, say the researchers. Exurban development and recreational activities, such as camping, have the potential to bring infested material, like firewood, directly into sensitive ecosystems. The researchers claim the key to early detection is through careful monitoring of human activity in coastal states and other vulnerable urban areas.
"A challenge for detecting invasive pests in urban and nearby ecosystems is the fragmentation of the landscape and the many ownerships involved" says Colunga-Garcia. "Public participation in monitoring efforts will perhaps be the most economic and ef
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Ecological Society of America