- Recent research, finds that 61 invasive species led to a cumulative cost of US$ 326.7 billion in urban areas between 1965 and 2021 globally, with an average annual cost of US$5.7 billion.
- According to the researchers, these costs are likely underestimated, as only 24 countries have reported losses, and there are no estimates available from 73 additional countries, including India.
- Most of these costs were attributed to damage by insects and impacted mostly public and social welfare.
- More studies and accurate cost reporting are needed for invasive species in urban areas, to plug taxonomic and geographic gaps.
New research shows that invasive species taking over urban areas resulted in a total cost of US$ 326.7 billion, at the very least, in the past five and half decades.
About 15% of the cumulative costs associated with biological invasions worldwide occurred in urban areas, which cover less than 3% of the Earth’s surface, according to a report by a global team of scientists. Most of these costs were attributed to insect damage and impacted public and social welfare.
Although invasive species are known to cause large ecological and economic losses, their economic impacts in urban areas are poorly understood, the report says. Therefore, the scientists synthesised the reported economic costs of invasive species in urban areas using InvaCost database, a compilation, and description of economic costs of biological invasions worldwide, to form a global estimate.
The results, published in Science of the Total Environment, show that 61 invasive species led to a cumulative cost of US$ 326.7 billion in urban areas between 1965 and 2021 globally, with an average annual cost of US$ 5.7 billion. These costs are “likely underestimated,” it says, as only 24 countries have reported losses, and there are no estimates available from 73 additional countries, including India, which have invasive species. “These results highlight the conservative nature of the estimates and impacts,” and “we emphasize the urgent need for more focused assessments of invasive species’ economic impacts in urban areas,” the scientists report.
Insects were responsible for more than 99% of reported costs, an estimated US$ 324.4 billion, followed by birds causing losses worth US$ 1.4 billion and plants causing losses worth US$ 494 million. The reported costs were highly uneven, with the sum of the five costliest species representing 80% of reported costs, the report says.
Most—77.3%—of the reported costs were damage-related, principally impacting ‘public and social welfare,’ and were almost entirely in terrestrial environments. The ‘public and social welfare’ category includes local infrastructures such as electric systems, quality of life such as income, recreational activities, and personal goods such as private properties and lands, and public services such as transport and water. Tourism, trade, conservation agencies, and forest services are also included.
Gustavo Herringer, a scientist at Nürtingen-Geislingen University in Nürtingen, Germany, and one of the study authors, told Mongabay-India that the findings show “the importance of urban areas to understanding and reducing the economic impact of invasive species.”
Equally significant is that “most economic impacts were attributed to damage, that is, the cost incurred to compensate, reduce or fix the damage, he adds.
Alok Bang, a co-author and researcher at Society for Ecology Evolution and Development, Wardha, says, “Earlier, there was a massive gap in our understanding related to the impact of urbanisation on the economic impacts of biological invasions.” Bang says there have been studies on urbanisation and specific invasive species, regions, ecosystems, or sectors. “Although these specific studies have been valuable, a global analysis and knowledge synthesis around the topic have been missing,” he adds. According to him this study’s significance is that it quantifies the economic impacts of urbanisation; it identifies the species causing these impacts, and highlights gaps in knowledge.
Better understanding the costs associated with invasive species is important to help inform management, influence legislation, and fund meaningful mitigation efforts, explains Jesse Borden, a researcher at the School of Natural Resources and the Environment at the University of Florida, who was not associated with the study. “The new research does a good job of summarising these costs specifically within an urban context. I find it particularly interesting that the authors found the majority of urban costs were associated with direct damages caused by invasive species, not management,” Borden tells Mongabay-India.
“Understanding and characterising the impact of invasive species in urban areas is very helpful, as that is where most humans live and where we might see the most direct impact on human livelihood.” Borden says framing ecological and environmental issues around financial costs can effectively inform legislation, justify conservation actions, and raise awareness about different issues.
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A paucity of data
“Although the impact is huge, it comes from only a handful of regions and species. There are a lot of regions where these species are found, but sans any reports of impacts,” points out Bang.
An example is India, where urbanisation has no cost despite the existence of many of these species. In developing economies such as India, environmental crises are equated with climate change, and other environmental crises, such as biological invasions, are not even documented well, says Bang.
India ranks second in the global list of countries ranked by the economic impacts of biological invasions. A 2022 study by Bang and colleagues reports that India has suffered US$127 billion worth of damages due to the cost of managing invasive alien species in the last six decades, averaging US$2-3 billion annually. However, there is no data specifically looking at urban areas.
“This conveys to me that the average of US$ 2-3 billion (per year) is an underestimate, and the actual costs would be much higher if the costs due to urbanisation were documented and were present in the public domain,” says Bang. “This is a huge economic burden for any country, but especially for a country with a developing economy.”
Bang says that the 24 species reported to cause the global economic impacts of urbanisation need to be studied in the Indian context. “Some of these species could already be here, and hence, we should already have a management plan to contain them.”
“Some of these species have arrived in our neighbourhood, but have not yet entered India. So we should have a border security plan to avoid their entry in India,” says Bang. Some of them are found in distant lands but in places with climate patterns similar to India. “This means that although they might not be close to India if they gain entry via trade, transport, and tourism, they may become problematic,” he cautions.
With 476 million Indians living in urban areas in 2020, “this points to an immediate relocation of priorities, resources, and research on this issue,” he adds.
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The success of urban invaders
The latest report adds to previous findings on invasive species taking over urban areas. A team of scientists from Brazil and Canada who studied the invasive guppies (Poecilia reticulata) reported in the Journal of Animal Ecology that guppies from urban streams are bigger, more in numbers and have more offspring than non-urban guppies, as urbanisation increases the availability and consumption of highly nutritious food by guppies and their fertility; and enhances the invasive potential of guppies.
Another group of scientists, which includes Borden, reported that an urban environment enhances the ecological opportunity for invasions by other alien species, the mechanisms of which are not fully understood. Borden says that the changes associated with urban areas “create a whole new ecosystem with novel conditions, resources and selection pressures” for species. “So, urban areas can select for specific traits, or even drive novel evolution in traits that could possibly enhance a species invasive potential.”
Borden cites the example of the cabbage white butterfly, an invasive agricultural pest originally from Europe, which has been shown to have larger wings in urban areas, a trait thought to help the butterfly disperse further between habitat patches. This butterfly is also a highly invasive agricultural pest, and if urban areas favour the selection for bigger wingspans and greater dispersal ability, this will enhance the invasive species’ ability to spread and impact larger areas, explains Borden.
Urban areas can be seen as a global habitat, but they cover different environments, species, and stakeholders, says Herringer. Hence, better communication with other scientists, citizens, managers, and decision-makers will contribute to increasing awareness about the topic and driving evidence-based decisions.
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Banner image: A blue rock pigeon in Mumbai. Rock pigeons are now found in almost every city in the world. Photo by ADARSHluck/Wikimedia Commons.