When new species of reptiles or amphibians invade a region where they are not indigenous, funds are often spent to eradicate them or to cope with the damage they cause. Funding for these operations can run to millions of US dollars, say the authors of a new review study aimed at assessing the global economic costs of amphibian and reptile invasions between the years of 1986 and 2020.
For the study, Ismael Soto and colleagues used data from the InvaCost database, which compiles estimates of the economic costs of species invasions. In addition, information was taken from numerous peer-reviewed articles, documents on governmental, academic and non-governmental organization webpages and documents retrieved from biological invasion experts.
The analysis, published in the journal Scientific Reports, estimates that between 1986 and 2020, the total cost incurred globally in coping with invasive amphibian and reptile species exceeded US$ 17.0 billion. Of this, US$ 6.3 billion was spent on dealing with amphibian invasions, US$ 10.4 billion was used to cope with invasions by reptiles, and the remaining US$ 0.3 billion was used in cases involving invasions by both amphibians and reptiles.
A total of US$ 6.0 billion (96.3 percent of money spent due to amphibian invasions) has been required to deal with the consequences of one single invasive amphibian species, the American bullfrog (Lithobates catesbeianus). This species is native to North America, east of the Rocky Mountains, but has spread in past decades to other regions of the US and Canada, and to numerous countries around the world. It is a voracious predator that eats almost anything it can fit into its mouth.
As far as invasive reptiles go, 99.3 percent of costs (US$ 10.3 billion) have been incurred dealing with brown tree snakes (Boiga irregularis). Native to eastern and northern coastal Australia, eastern Indonesia, Papua New Guinea, and many islands in northwestern Melanesia, this snake preys on vertebrates such as rodents, birds, bats and reptiles. It was accidentally introduced to the island of Guam shortly after the Second World War and was responsible for exterminating most of the indigenous forest vertebrate species on the island. It also caused power outages which affected private, commercial and military activity.
In order to prevent these snakes from being introduced accidentally from Guam to other Pacific islands, trained dogs are used to search, locate, and remove brown tree snakes before outbound military and commercial cargo and transportation vessels leave the island.
The study also found that 99.7 percent of costs due to invasive amphibians (US$ 6.3 billion) were incurred in managing these invasions, for example by eradicating the invasive species. In a similar finding, 96.6 percent of costs due to invasive reptiles (US$ 10.0 billion) were associated with managing damages caused by invasions, such as crop yield losses.
European countries incurred 96.3 percent (US$ 6.0 billion) of the cost relating to the management of amphibian invasions, while Oceania and certain Pacific Island countries incurred 99.6 percent (US$ 10.4 billion) of the cost relating to the management of invasive reptiles.
The authors suggest that the economic costs of amphibian and reptile invasions could be reduced by investing in measures to limit global transport of invasive species and to enable the early detection of invasions. This could reduce the need for long-term management of species invasions and the scale of damage incurred, they add.