Invasive species have cost the world $1.288 trillion at the absolute minimum since 1970, a new analysis has found, and the costs of damages are vastly outstripping the amount of money humans have spent on addressing the problem.
Looking at 1,319 separate costs reported only in official documents and peer-reviewed studies, the researchers found that from 1970 to 2017, the world spent an average of $26.8 billion per year on damages and management costs related to invasive invertebrates, vertebrates and plants. With a less stringent analysis — looking beyond just peer-reviewed and official materials — the costs were 33 times higher in 2017. North America alone was paying an average of $11 billion annually, and the worldwide cost may have been more than $47 billion in 2017.
The cost of invasive species generally isn't factored into policy — but it should be, the researchers argued.
"Biological invasions are a major driver of global change throughout the world, but societal and decision-makers' awareness still remain very low," said Christophe Diagne, the lead author of the study, which was published March 31 in Nature. "The damage level of biological invasions highlights the need of doing more in terms of management."
The cost of damages, which were all reported in 2017 U.S. dollars, increased at twice the rate of management costs in each decade. The problem, essentially, was getting worse, and the response wasn't keeping up, and the researchers were confident making this assertion because they found higher damage costs, even though they had far more reports of management costs — 402 damage reports compared to 878 management reports. There is, Diagne said, "a discrepancy between very high damage effects from biological invaders and low monetary investments from [international and national] authorities over time."
Although invasive species are a huge and expensive problem, policymakers aren't treating the issue with the attention and resources that are merited, Diagne said, so "using a common metric — currency — was one sound option to raise awareness on these invasions, and put emphasis on this increasing, planet-wide problem."
Diagne, a postdoctoral researcher at Paris-Saclay University, and his co-authors looked at reports in the InvaCost database, which Diagne and some of his co-authors helped build. Insects represented 90% of the cost of invertebrates, which overall cost the world $8.7 billion a year, on average. Some of the more reported species were mosquitoes, Formosan termites and fire ants, which were wreaking havoc along with vertebrates such as cats and rats.
The authors noted that the regions at the greatest risk for damage from invasive species are some of those with fewer resources to combat the issue: Areas in Africa and Asia are at particular risk. Meanwhile, the current costs in those regions are likely underestimated in this study, because lower-income countries simply weren't reporting as much data as higher-income countries.
The study also did not account for many harms caused by invasive species, "simply because not everything has a monetary value, in addition to the methodological difficulty of monetizing all impacts," Diagne said. "Diseases transmitted by biological invaders are associated with a cascade of indirect effect, e.g. loss of productivity and income, that are often lacking from cost estimation."
Moreover, he pointed out, "costs" such as human or animal life, the ability of native species to thrive and impacts on ecosystems are harder to quantify than money lost to crop damage. The full toll of invasive species is likely incalculable. Still, the authors wrote, the bill so far is "a compelling call for the implementation of consistent management actions and international policy agreements aiming to reduce invasive alien species burden."
The study, "High and rising economic costs of biological invasions worldwide," published March 31 in Nature, was authored by Christophe Diagne, Anne-Charlotte Vaissière and Franck Courchamp, Université Paris-Saclay; Boris Leroy, Unité Biologie des Organismes et Ecosystèmes Aquatiques, Muséum national d'Histoire Naturelle, Sorbonne Université, Université de Caen Normandie, Université des Antilles; Rodolphe E. Gozlan, David Roiz and Jean-Michel Salles, Université de Montpellier; Ivan Jarić, Czech Academy of Sciences and the University of South Bohemia; and Corey J. A. Bradshaw, Flinders University.