The carcasses of spotted lanternflies that now litter the streets of New York City are not just gross, they are expensive.

The annual cost of invasive alien species now exceeds $423 billion annually, according to a new report by the Intergovernmental Platform on Biodiversity and Ecosystem Services, an organization that is a part of the United Nations.

The report claims over 37,000 so-called alien species have been transported due to human activities around the world. Over 3,500 of those are invasive, meaning they are harmful in that they threaten nature and how people benefit from nature.

Invasive alien species, as defined by the report, are species that are known to “have become established and spread, which cause negative impacts on nature and often also on people.”

The costs of invasive species have quadrupled every decade since 1970, according to the report.

Coordinating lead author for the report Martin Nuñez said the $423 billion estimate is a gross underestimate and the true cost is more likely in the trillions, with human health complications taking up a large part of that price. He cited mosquitos in developing world, which carry diseased like malaria, Zika and West Nile Fever. They are spread by alien mosquito species like Aedes albopictus and Aedes aegyptii.

In the case of the spotted lanternflies plaguing New York, the state estimates the flies, which arrived from China, could cost at least $300 million annually, mainly to the grape and wine industry.