New research published in the journal Nature estimates that invasive species have cost at least $1.288 trillion globally from 1970 to 2017, with an annual mean cost of $26.8 billion. These expenses come from the cost of trying to eradicate invasive species as well as the loss of crops, disease transmission, and infrastructure damage. Researchers say that the costs are likely well underestimated and that these costs have roughly doubled every six years; in 2017 alone, the cost was estimated at $162.7 billion. The proliferation and spread of invasives likely occurred through rapidly increasing global trade, and that deforestation and agricultural may have aided in expansion.

“For decades, researchers have been evaluating the significant impacts of invasive species, but the problem isn’t well known by the public and policy makers,” says Boris Leroy, a biogeographer at the French National Museum of Natural History in Paris. “By estimating the global cost, we hoped to raise awareness of the issue and identify the most costly species.”

Study authors conducted detailed review of 1,900 published papers to arrive at their cost estimates. Based on this analysis, the top five most costly invasive species are mosquitoes, rats, cats, termites, and fire ants. However, existing science has gaps as research is heavily weighted towards North America, Europe and parts of Asia and Oceania. In addition, agricultural pests, like insects, tended to be overrepresented in published literature compared with invasive plants.

The study is summarized in ScienceNews.