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Plants and animals often hitch rides on airplanes and cargo ships. These newcomers can devastate crops and wipe out native species. And historically, these invasive species were seen as a bigger problem for wealthier countries. But new research in the journal Science suggests that poorer countries experience more harm. NPR's Jonathan Lambert has more.
JONATHAN LAMBERT, BYLINE: Invasive species can be devastatingly opportunistic. Plopped into a new environment, they're often free of the species that keep them in check back home and can go hog wild. Sven Bacher is an ecologist at the University of Fribourg. He points to the example of the fast-growing plant, the water hyacinth.
SVEN BACHER: Which covers entire lake ecosystems, smothering the entire lake, filtering out all the light that gets to the ground. The fish are dying. Local fisheries actually have to give up.
LAMBERT: It's one example of thousands that scientists have studied in recent decades. The bulk of that research has happened in wealthier countries in North America and Europe, sometimes referred to as the Global North. That focus...
BACHER: Might have created the impression that this is actually a problem rather of developed countries with all the economy and all the exchange of goods and so on.
LAMBERT: But these biological invasions happen in the Global South too. Water hyacinth, for example, is choking off waterways in Nigeria right now. And while there are way fewer studies outside of wealthy countries, there are some. Bacher and his team cooked up a way of comparing the impact in different regions by averaging across studies.
BACHER: You can get a value that you can directly compare.
LAMBERT: He and his colleagues analyzed data from over 22,000 instances of invasive species causing some kind of change in a natural environment. They looked to see on average whether these impacts were small or large in a given region for a given species. The pattern was striking.
BACHER: You see that regions in the Global South - and not just some, like all over the Global South - suddenly, it shows that the impacts on average are much higher.
LAMBERT: That pattern wasn't entirely surprising to Anibal Pauchard. He's an ecologist at the University of Concepcion in Chile. He praised the study and thinks it offers a couple early hints as to why invasive species could be causing more problems in low- and middle-income countries.
ANIBAL PAUCHARD: Countries or communities with lower resources will be more impacted because their lifetimes are dependent on natural resources, and also because they don't have the tools to avoid or adapt to the changes caused by invasive species.
LAMBERT: In fact, the study found that the weaker a government's capacity to respond, the worse the impact of an invasive species. Also Pauchard thinks that many of these countries have more biodiversity to lose.
PAUCHARD: Biodiversity is under threat, and changes are very visible. Many of these countries have been changing only in the last hundred years or 200 years. Instead, Europe has changed for a long time.
LAMBERT: So a single invasive species can cause a lot of harm. He points to eucalyptus trees, which have invaded many parts of South America and Africa. These trees can take over and suck up a lot of water.
PAUCHARD: In the Global North, you can find, you know, new ways to get water from more faraway resources. But in the Global South, you're really dependent on the water that gets really close to your community.
LAMBERT: Invasive species are a global problem, but Pauchard says this study shows how solutions must be tailored to specific places. Figuring out those solutions, he says, will require greater cooperation between the Global North and the Global South.
Jonathan Lambert, NPR News. Transcript provided by NPR, Copyright NPR.
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