Invasive species are wreaking havoc on ecosystems all over the world. Now, researchers say that a 20-30 percent increase in these alien species would result in a massive loss of biodiversity in future.
Plants, animals, fungi and other organisms are described as "invasive" when they are not native to a specific location.
They spread around the globe with the help of human activities, such as global trade and transportation, and can be introduced either intentionally, through the pet and horticultural trade for example, or unintentionally, as stowaways in cargo or in the ballast water tanks of large ships, among other pathways.
The impact of invasive species on their new environments can be significant in some cases. For example, they can displace native species—sometimes leading to local extinctions—while also altering the functioning of ecosystems.
In addition, invasive species even have a negative effect on economies (for example, via introduced crop pests) and human health, through the transmission of disease.
Researchers already have a relatively good understanding of how invasive species have spread around the world. But what is not so clear is what the likely future impacts of biological invasions will be.
In order to address this question, an international team of researchers led by Bernd Lenzner and Franz Essl from the Department of Botany and Biodiversity Research at the University of Vienna, Austria, conducted a survey of 36 leading experts in biological invasions for a study published in the journal Global Change Biology.
"Several studies have already shown that impacts from invasive alien species are increasing and that this trend is likely to proceed in the future," Lenzner told Newsweek.
"To get a better understanding about this trend we decided to consult a group of leading scientists in invasion science to share their insight on how this is going to develop under two plausible future scenarios—a best case where human societies act decisively on the causes of invasions and a worst case scenario with only little action in that regard," he said.
Based on the responses, Lenzner and Essl estimated that a moderate 20-30 percent increase in invasions compared to current conditions would be expected to cause dramatic biodiversity loss around the globe. According to the researchers, this threshold could be reached soon given that the number of invasive species is constantly rising.
The study also identified the main drivers that are going to be important in the future with respect to biological invasions: global transport, climate change and socio-economic change—such as energy consumption and land use changes.
Furthermore, the study found that other drivers would be significant in certain parts of the world, for example, tourism in tropical and subtropical regions.
"We demonstrated that, based on expert knowledge, there is a high risk of increased potential future impacts of biological invasions due to many drivers," the authors wrote in the study.
Finally, the researchers said that in some best-case scenarios, the future impacts of biological invasions could be significantly reduced. However, for these to become reality, rapid and comprehensive global actions will be required, according to the authors.
"[The study] provides an important scientific basis for the further development of international agreements such as the Sustainable Development Goals or the Convention on Biological Diversity. This way we will be able to reduce the negative impacts of alien species on global biodiversity and our society," Lenzner said.
Helen Roy, a co-author of the study from the U.K. Centre for Ecology & Hydrology, said in a statement: "There has been a rapid escalation in the number of non-native species being transported and introduced by humans around the world. It is now critical that we work collaboratively to predict future patterns so that we can inform appropriate action going forward—such as improved biosecurity—to prevent further introductions of the most damaging invasive non-native species."
Among the most famous examples of an invasive species are the hippos that
Colombian drug lord Pablo Escobar imported into the country in the early 1990s to live in his luxurious country estate.
In a recent study published in the journal Ecology, a team of scientists found that the hippos—which have multiplied and expanded outside the estate in the years since Escobar's death—are having a big impact on the local ecosystem, with potentially "negative consequences" for water quality in the surrounding lakes.
In the U.S., more than half of National Parks are struggling with invasive species, with some of the worst offenders being invasive rats, feral cats, feral hogs and the Burmese python, according to a study published in the journal Biological Invasions. The latter's introduction to the Everglades National Park in Florida has led to an estimated 60 percent reduction in the number of birds and mammals over the last twenty years or so.
"Invasive rats, cats, and mosquitos carrying disease (avian malaria) have caused the extinction of endemic island birds in the Pacific, such as Hawaii," Ashley Dayer, an author of the paper from Virginia Tech and the Department of Fish and Wildlife Conservation, previously told Newsweek.
"There and throughout much of the U.S., feral hogs destroy wildlife habitat impacting birds and small mammals. Likewise, feral cats are considered to be among the most destructive invasive species globally for their predation of birds and other animals."
The latest Global Change Biology paper was published soon after another study, which found that invasive bee species have contributed to a 94 percent loss of plant-pollinator networks over the last 30 years in northeastern North-America.
Pollinator networks consist of wild bees and the native plants that they historically rely on. However, according to a study published in the journal Insect Conservation and Diversity, 30 percent of these networks in the region have been completely lost, meaning either the bees or plants had disappeared, or both. Meanwhile, a further 64 percent of the loss is accounted for by bees no longer visiting certain plants.
The researchers say that climate change is likely the biggest driver of the pollinator network losses, however an increase in non-native bee species, which have displaced some native species, may also be playing an important role.
"We are getting a lot of invasive species and new records of invasive species every year. This is usually accidentally through trade and through ornamental plants," Sandra Rehan, an author of the paper from York University in Toronto, Canada, said in a statement.
This article has been updated to correct Sandra Rehan's title.
