Disease-carrying mosquitoes, crop-ravaging rodents, forest-eating insects and even the domestic cat are all "exotic" intruders whose cost to humanity and the environment is vast and growing, according to a sweeping study published Wednesday. Researchers in France estimate that invasive species have cost nearly $1.3 trillion dollars to the global economy since 1970, an average of $26.8 billion per year. And they warn that this is likely an underestimate. In a study published in the journal Nature , scientists totted up the dizzying array of harmful effects from species carried between habitats, whether plants, insects, reptiles, birds, fish, molluscs, micro-organisms or mammals. Beyond the "phenomenal magnitude" of these costs, there is also sign of a steady upward trend since 1970, said lead author Christophe Diagne, of the Ecology, Systematics and Evolution laboratory at the University of Paris-Saclay. Most of the price tag is associated with the damage to ecosy
