Between 1986 and 2020, introduced amphibians and reptiles cost the global economy approximately €16.5 billion. As an international working group headed by Phillip Haubrock from the Senckenberg Research Institute and Natural History Museum in Frankfurt reports in the journal Scientific Reports, two species are mainly responsible for the costs mentioned: the brown tree snake (Boiga irregularis) and the North American bullfrog (Lithobates catesbeianus). The animals decimate native species, which in turn destabilizes ecosystems, leads to the spread of diseases among animal species and causes crop losses.
For their study, the researchers evaluated information from the InvaCost database, which contains scientific studies and documents from governments, universities and NGOs. Haubrock and his team came to several conclusions: Out of a total financial loss of around 16.5 billion euros, invasive amphibians accounted for 6.1 billion euros and imported reptiles for 10.1 billion euros. 200 million euros go back to both groups of animals. For frogs, toads or amphibians, the costs arise from fighting the animals. Reptiles, on the other hand, are increasingly causing damage, for example in fields.
The distribution of the costs varies around the world. Oceania and the Pacific Islands contribute about 63 percent, Europe about 35 percent, and North America two percent.
Where the bullfrog and the tree snake were introduced
On the western Pacific island of Guam, for example, there are more than 10,000 brown tree snakes per square kilometer. During World War II, US troops had introduced the reptile. After a few years, the snakes ate numerous native bird species, which are now extremely reduced or even extinct. In addition, the snakes on Guam cause a number of power outages, which in turn generates repair costs. In Europe, on the other hand, the amphibians are more likely to make a difference. Fighting the North American bullfrog alone devours 95 percent of all expenditure there.