The number of ‘aliens’ on Earth is increasing, but it is not what you think. Invasive species can disturb entire ecosystems and it is difficult to address them. A new international research revealed that the number of newly emerging so-called alien species is still increasing – around 16% of all species on Earth could qualify as potential alien species and could negatively affect other regions – even when those species are coming just from other locations of our planet.
Scientists from the Senckenberg Biodiversity and Climate Research Centre, the University of Vienna and UCL took a look at a database, including 45,984 records detailing the first invasions of 16,019 established alien species from 1500 until 2005. They found that in recent years the number of previously unrecorded invasive species grew and that is a problem. Current preservation methods rely on a notion that those species that had been registered as invasive before are likely to invade new regions. This lets new alien species to slip through protective measures.
Even though in the proportion of newly emerging alien species in plants, mammals, and fishes has remained constant for 150 years, the number of total alien species has increased anyway. In 2000-2005 a quarter of alien species were new. The worst situation is in insects, molluscs and other invertebrates, because they have the highest proportion of emerging alien species. This is quite worrying. People have been moving animals around out of their natural habitats for ages, which made us think now that emerging of new invasive species is sort of unlikely. However, a quarter of the new cases are emerging alien species. In previous studies increase in alien species has been attributed to human activity, but now statistics show that this is not always the case.
While humans are to blame for destroying habitats and moving species around, increases in import volumes, human mobility and land-degradation is not responsible for the entire increase in the number of alien species. Dr Ellie Dyer, co-author of the study, said: “These findings will be extremely helpful for horizon scanning studies that aim to identify “door knocker” species, which are those not yet recorded but are suspected of presenting a high risk of arrival and detrimental impacts”.
Interestingly, preventive measures are actually effective in what they do. Scientists have managed to decrease the number of alien species from established sources. However, this did cause an increase in new emerging invasive species that have not been seen to move to new habitats before. Therefore, preservation methods will have to be updated to address this situation.