Europe the hotspot for alien species

The number of alien species, particularly insects, arthropods and birds, is likely to increase by 36% globally by the middle of this century compared to 2005, according to a new study.

Europe will feel the brunt of this, it predicts, with the arrival of around 2500 new non-native species – an increase of 64% for the continent over the 45-year period.

The findings, by an international research team led by Germany’s Senckenberg Biodiversity and Climate Research Centre, are published in the journal Global Change Biology.

Alien species are those that humans have moved around the world to places where they do not naturally occur. They can become invasive, and are one of the main drivers of extinctions of animals and plants.

More than 35,000 such species had been recorded by 2005, when the most recent comprehensive global catalogue was compiled.

For the new study, lead author Hanno Seebens and colleagues developed a mathematical model based on estimated sizes of source pools and dynamics of historical invasions, under a business-as-usual scenario that assumes a continuation of current trends.

It identified high levels of variation, with temperate latitudes of Asia, North America and South America considered hotspots after Europe. The lowest relative increase is expected in Australia.

“Increases are expected to be particularly large for insects and other arthropods, such as arachnids and crustaceans,” says co-author Franz Essl, from the University of Vienna, Austria.

“We predict the number of aliens from these groups to increase in every region of the world by the middle of the century – by almost 120% in the temperate latitudes of Asia.”

The study also predicts that the rate of arrival of alien species will continue to increase, at least in some animal groups.

Globally, by 2050, alien arthropod and bird species in particular will arrive faster than before, compared to the period 1960 – 2005. In Europe, the rate of new alien arrivals is expected to increase for all plant and animal groups except mammals.

Neither a reversal nor a slowdown in the spread of alien species is in sight, the researchers suggest, as global trade and transport are expected to increase in the coming decades, allowing many species to infiltrate new habitats as stowaways.

But, says co-author Tim Blackburn from University College London, “we are not helpless bystanders”, and with “a concerted global effort to combat this, it should be possible to slow down or reverse this trend”.