Invasive reptiles and amphibians have cost the global economy billions, study suggests

Invasive reptiles and amphibians have cost the global economy more than $17 billion US between 1986 and 2020, a recent study suggests.

The analysis, published this week in the journal Scientific Reports, says the transportation of "alien species" into new areas is increasing at an unprecedented rate due to the globalization of human activity, and that this can lead to species invasions and extinctions of indigenous species, damage to ecosystems and major economic impacts. 

It is "almost impossible" to list all the ways invasive species can affect an economy, said Ismael Soto, the study's lead author and a PhD student at the University of Bohemia in Plzeň, Czech Republic.

For example, he said, those economic costs can reach as far as the real estate market if an invasive species becomes a pest that is "impossible to live near."  

Soto cited the Burmese python, which is invasive to the Florida Everglades and creates a dangerous environment for surrounding residents. He also pointed out that a brown tree snake invasion in Guam has coincided with house prices there falling over time. 

"The economic costs are massive for all invasive species," said Soto. "We have to try and be aware of these costs and take control of the management of these species." 

The study breaks down the estimated $17 billion US cost into: $6.3 billion spent dealing with invasive amphibian species; $10.4 billion on invasive reptiles; and $300 million on cases involving both.

To conduct the analysis, Soto and other colleagues used a database, InvaCost, which attempts to bring data on economic invasive species together. Most of the figures were taken from peer-reviewed literature or studies determined to be of high reliability, but they note that they largely came from estimates and extrapolations, rather than empirical observations.

Gaps in research

According to Soto, the economic costs of invasive species are under-documented worldwide. While conducting the study, researchers had difficulty finding records in North America and Africa in particular, he said.

"We found that there are costs in all continents," said Soto. "But maybe there is just not enough research relating to economic costs in these areas." 

Monitoring the economic impact of invasive species is a relatively new area of research and has the potential to grab the attention of Canadians, says Colin Cassin, policy manager at the Invasive Species Centre (ISC), a non-profit based in Sault Ste. Marie, Ont.

"Some people may have no interest in the ecological impacts of invasive species, but what speaks to them is the fact that their house value just declined," said Cassin.

Such research is "an opportunity for us to connect with different audiences and make sure that everyone understands the far-reaching implications." 

Canada does not have an environment where many invasive reptiles and amphibians can thrive, Cassin said. There are some examples — such as the red-eared slider, an invasive turtle species — but they are not among Canada's most costly invaders.

According to the International Union for the Conservation of Nature, invasive species are among the most significant threats to biodiversity. 

While not all introduced species are able to flourish in a new environment, some find the right conditions. They are usually able to reproduce and spread quickly, often out-competing native plants and animals for food, water and space. 

Japanese knotweed, zebra mussels and the emerald ash borer have all wreaked havoc in parts of Canada.

Last year, the ISC conducted a cost-benefit analysis of phragmites, an invasive grass in Canada that does well in wet environments such as drainage ditches. 

The study looked at the costs of roadside maintenance and flooding related to the grass, but also took a deeper look at potential impacts on a driver's sightlines and whether there were increased costs due to traffic accidents. 

"There is a lot out there with respect to how much invasive species cost us that is either being understood right now or has yet to be understood," said Cassin.