The U.S. Department of Agriculture defines invasive species as non-native to an ecosystem and likely to cause environmental, health or economic harm.
The department's recent actions included detection or removal of species alien to North American locations. Some species spread disease among bats; others such as weeds displace or destroy vegetation in natural habitats.
More seriously for humans, invasive species could be manipulated to become biological weapons, researcher Lawrence Roberge said in a doctoral dissertation at Atlantic International University in Honolulu.
"In the hands of a rogue nation, terrorists, or an individual bent on destruction, an invasive species could have an affect similar to better known potential biological weapons such as smallpox or anthrax," said Roberge, an associate professor of anatomy and physiology at Laboure College in Boston.
In the study, Roberge explored multiple threats posed by invasive species consumed or carried by birds, feral pigs, ticks and various kinds of insects and plants.
Feral pigs can be used to carry the Nipah virus and spread disease among humans, cattle and wildlife, he said.
The heartwater pathogen is a microbe that can cause heart and pulmonary edema. When carried by the tropical bont tick, it can kill deer, cattle or other wildlife, and potentially be transmitted to humans.
The striga plant parasite can destroy corn crops and subsequently devastate commodity markets and biofuel production.
Barberry plants eaten by birds can spread wheat stem rust, causing a decline or destruction of wheat production.
He said invasive species could be used to selectively destroy parts of a society potentially causing chaos, food shortages and other forms of mass destruction.
"These types of weapons are inexpensive to produce and hard to detect immediately, so they can cause extensive damage before they can be controlled," he said.
A nation under such an attack might find it difficult to respond to an outright attack. "We must prepare for the use of invasive species as biological weapons," Roberge said.
More extensive research and record keeping is the answer, he added.
He called for the creation of a global database of biocontrol agents such as predators, pathogens and parasites, expansion of global reporting on invasive species and genomic mapping for known and high-risk, non-indigenous organisms.
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