Whether accidentally or deliberately introduced, certain species have now become the second most common threat associated with recent global extinctions of animals and plants.
A new study conducted by the University of Adelaide and UCL in the U.K., has found that since transnational shipping started in 1500 AD “alien species” have now spread beyond their natural locations by both deliberate and accidental human intervention, with many having a significant negative environmental impact.
Professor Tim Blackburn, Professor of Invasion Biology at UCL and Visiting Professorial Fellow at the University of Adelaide and the study leader, said:
“Our results show that alien species are the second most common threat associated with species that have gone completely extinct from these groups since 1500AD.”
According to the University of Adelaide:
“Alien species are just behind the most common threat averaged over all five groups — the most common being overexploitation of biological resources. They are, however, the most common threat associated with extinctions in each of three of the five groups analyzed (amphibians, reptiles, and mammals), and the most common threat when averaged over all the vertebrates (birds, amphibians, reptiles, and mammals).
“Across the globe, Australia has the highest rate of recent mammalian extinctions in the wild. Co-author Associate Professor Phill Cassey, Head of the University of Adelaide’s Invasion Ecology Group in the Environment Institute, says human activities were clearly raising extinction rates, and the introduction of alien species is one of the leading causes.”
“This study clearly shows the consequences of human participation in indirect species extinction.
“Many of these introductions have come through the legacy of European colonization and the associated acclimatisation of animals and plants, which have become pests and weeds.
“However, with increased globalization we now have a new suite of biological invaders: zoonotic diseases which because of airborne travel can arrive in the country in less than a day; and a large illegal biological trade in wildlife. This latter group is probably the least known, and therefore of considerable concern.
“The problem is that once these introduced species become established, eradication can be incredibly difficult. That is why we need such stringent biosecurity and to remain vigilant.”
In Australia, the “classic cases” of introduced mammalian species that impact biodiversity, and are causing extinctions, are generally herbivores such as rabbits, goats, pigs, and camels, with the predators being feral cats and foxes.
“There have been a number of small to medium-sized Australian mammals now extinct because of these predators,” Cassey adds.
The study published in the journal, Biology Letters, assessed how common alien species were listed as drivers of recent extinctions in plants, amphibians, reptiles, birds, mammals, using data from the IUCN Red List.