Invasive species can wreak havoc on local ecosystems. Cleaning up biological waste comes at a huge price.
These invaders, often pushed into new environments by humans unintentionally (or intentionally, to combat pests), can transmit new diseases, devastate crops, and eat up crucial infrastructure. From 1970 to 2017, these invasions cost the world economy at least $ 1.28 trillion in damage and efforts to control them, researchers report on March 31 in Nature. As the globe becomes more interconnected and invasive species take on new habitats, that cost grows.
“For decades, researchers have been evaluating the significant impacts of invasive species, but the problem is not well known to the public and policymakers,” says Boris Leroy, a biogeographer at the National Museum of Natural History in Paris. "In estimating the overall cost, we hoped to raise awareness about the problem and identify the most expensive species."
Leroy and colleagues examined more than 19,000 published articles, finally analyzing nearly 1,900 that detailed the costs of various invasions at specific times. The team then constructed a statistical model that estimated annual costs, adjusting for factors such as inflation, different currencies, and time scales. Between 1970 and 2017, annual costs doubled approximately every six years, reaching an annual bill of $ 162.7 billion in 2017.
Researchers claim that intensified world trade during that period gave the invaders more opportunities to engage cargo ships or aircraft. And deforestation and agricultural expansion have likely accelerated their expansion by allowing easier access to virgin areas.
Overall, clearing the damage caused by invasive species cost $ 892 billion, about 13 times more than the $ 66 billion spent on managing invasions, the researchers found.
“This is a really ambitious endeavor,” says Helen Roy, an ecologist at the UK Center for Ecology and Hydrology in Wallingford, England. “There are big gaps in the data, about which the authors are extremely transparent,” he says. The analysis was heavily weighted toward North America, Europe, and parts of Asia and Oceania. Agricultural pests, such as insects, tended to be over-represented in the published literature compared to invasive plants.
“Still, having a global look is very important,” Roy says. Although this number is almost certainly underestimated, she says, the study "shows us that this is a huge problem that is getting worse." Investing more in cargo inspections and other biosecurity or monitoring measures could help minimize these costs with relatively small spending increases. “It’s much cheaper than waiting for the species to settle and spread widely before responding,” he says.
Here’s a closer look at the five most expensive invasive species.
1. Aedes mosquitoes (A. albopictus and A. aegypti): about $ 149 billion
The Asian tiger mosquito (A. albopictus) arrived in the United States in the mid-1980s, hitchhiking on used tires shipped from its native Asia. First detected in Houston, it quickly spread to 40 states. It also invaded parts of Europe, South America, Africa and Australia. A. aegypti, or the yellow fever mosquito, is native to sub-Saharan Africa and spreads around the world by similar methods.
Together, these two mosquitoes cause significant damage to public health by transmitting a number of diseases such as Zika, chikungunya, yellow fever and dengue, which account for most of their cost. As mosquitoes spread, the toll of these diseases increases (SN: 20/11/19).
2. Rattus: About $ 67 billion
The global occupation of these rodents comes from approximately 3,000 years of hitchhiking on human ships. Once they reach a new location, rats often outnumber other small mammals, but they can also harm birds and aquatic species. On islands around the world, rats have led many species to extinction. For example, the Pacific rat, native to continental Southeast Asia, has suffered from at least 1,000 species of island birds. The high cost of rats comes from these biodiversity losses, but rodents can also damage crops, destroy properties, and transmit diseases (such as bubonic plague).
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3. Felis catus (cats): about $ 52 billion
Native to Europe and the Middle East, our feline friends have settled on every unfrozen continent. Cats are excellent predators and can make a fast food from a variety of prey, from insects to birds. According to some estimates, cats kill a billion birds each year in the United States alone (SN: 29/01/13). Most of the economic damage caused by cats cataloged in Leroy’s analysis comes from their impact on native biodiversity and the resulting losses in spending on bird watching and bird hunting such as ducks, pheasants, and capercaillies.
4. Coptoterms formosanus (termites): about $ 19 billion
These underground termites native to East Asia have spread around the world through trade. Termites can thrive as long as there is cellulose (such as wood) and moisture, which has helped them quickly establish colonies as they enter a new region. His appetite for wood can wreak havoc on all sorts of structures, from houses to bridges. Although they can also damage crops and tree holdings, their high cost in this analysis is summed up in their impact on infrastructure.
5. Solenopsis invicta (fire ants): about $ 17 billion
Fire ants typically become the dominant ant species when introduced into a new region, due to their aggressive feeding tactics, which include powerful stings and stings. Native to South America, these ants arrived in the United States in the 1930s by boat, most likely transported to the region's soil. They have also spread to Australia, New Zealand, China and around the Caribbean. Fire ant colonies have a wide impact; they can feed on a variety of seedlings, from citrus to soybeans, reduce the size of grazing land for livestock, and bite and sting farm animals and humans.