AMHERST, Mass. - In the first global analysis of environmental risk from invasive alien species, researchers say one sixth of the world's lands are "highly vulnerable" to invasion, including "substantial areas in developing countries and biodiversity hotspots."

The study by biogeographer Bethany Bradley at the University of Massachusetts Amherst and Regan Early at the University of Exeter, U.K., with others, appears in the current issue of Nature Communications.

As Bradley explains, "First, we analyzed threats of invasive species introduction and establishment globally. Then, we took a look at national policies to see how prepared we are to combat these threats. Our results show some pretty clear vulnerabilities--high risk, but few policies to deal with invasion. We hope that by raising awareness of the highest risk areas, maybe we can help to jump start a more proactive policy response."

Noting that "most countries have limited capacity to act against invasions," the researchers say there is a "clear need for proactive invasion strategies in areas with high poverty levels, high biodiversity and low historical levels of invasion." By collecting data on how invasives are introduced and established, and assessing national response capabilities around the world, they hope to "improve early warning and eradication schemes."

Bradley says, "Invasive species are a threat to ecosystems and economies worldwide, but are most concerning in countries with few resources to deal with them." Examples of biological invasion in the developing world include Panama disease, which is wiping out banana plantations in Central and South America, and prickly pear, which devastates grassland important not only to wildlife but to farming in Africa.

Bradley and colleagues found that the dominant pathways by which invasives are introduced differs by income, with higher-income countries facing the highest risk from imported exotic plants and pets, while low-income nations face the highest threat from air travel, as invasive species stow away in passenger baggage. They expect air travel to bring future biological invasions of Africa and Asia, for example, regions that are currently becoming increasingly vulnerable to invasion due to climate change and intensifying agriculture.

In documenting national policies on invasive species now in place around the world, the researchers characterize them as either proactive or reactive, but Bradley notes that "proactive policies are remarkably rare. We generally do a pretty good job of identifying invasives after they've become a problem, but a terrible job of keeping them out."

"Another thing we found is that some countries have created excellent, comprehensive lists of invasives, while their near neighbors have no information at all. This illustrates a really good opportunity for cooperation and exchange of information. Nations with more invasive species research and management experience could help their neighbors leap ahead just by sharing information. The information is definitely there in many cases," she adds, "but many cooperative efforts are still a work in progress."

Study leader Early notes that "rampant globalization will lead to invasions in countries with the least capability to deal with them. We need more international cooperation, and for the U.S., Australia and nations in Europe to share expertise." While rich nations are accustomed to the nuisance of invasive alien species and are increasingly taking protective action, the authors found that poorer economies rely on international trade and have little power to regulate imports, so highly dangerous species continue being introduced unchecked.

Overall, Bradley says an obvious recommendation from this work is that nations need to be more proactive. She says, "It's really clear that even in the U.S., where we know that new invasives arrive every day and we understand the pathways for how that happens, for example that 60 percent of invasive plants have been introduced as ornamentals, we could do a better job."

"If you want to know what the invasive species problem is going to look like in 2100, take a look at the new 'exotic' plants you're putting in your yard today. If you want new plants, buy local. If you get tired of your exotic pet snake, don't release it outdoors. A lot of proactive work to reduce invasion risk relies on us -- the consumers -- to be more aware of the consequences of our actions."

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