Islands and coastal regions are threatened the most
Durham/Vienna/Leipzig. The distribution of established alien species in different regions of the world varies significantly. Until now, scientists were uncertain about where the global hotspots for established alien species are located. An international research team that includes Marten Winter and Carsten Meyer from the German Centre for Integrative Biodiversity Research (iDiv) and Leipzig University is the first to provide an analysis of these hotspots: According to their study, most alien species can be found on islands and coastal regions. The study was published in the renowned journal Nature Ecology and Evolution on 12 June 2017.
Humans are responsible for the movement of an increasing number of species into new territories which they previously never inhabited. The number of established alien species varies according to world region. What was previously unclear is where the most established alien species could be found and which factors characterise their distribution.
An international team consisting of 25 researchers under the leadership of Dr Wayne Dawson from the University of Durham (United Kingdom), who began his research on this topic at the University of Konstanz, created a database for eight animal and plant groups (mammals, birds, amphibians, reptiles, fish, spiders, ants and vascular plants) that were found to occur in regions outside of their original habitat. The study of the distribution of these species led the research team to identify 186 islands and 423 mainland regions in total. This project allowed the researchers to illustrate the global distribution of established alien species within a large number of organism groups for the first time.
Most important result: The highest number of alien species can be found on islands and in the coastal regions of continents. The island of Hawaii was found to have the most alien species, followed by the north island of New Zealand and the small Sunda Islands of Indonesia. The researchers also examined the factors responsible for the number of alien species in any one region. Lead author Dr Wayne Dawson, from Durham University’s Department of Biosciences, said: “Our research shows that, islands and mainland coastal regions contain higher numbers of established alien plants and animals, and this may be because these areas have major points of entry like ports. In general, regions that are wealthier, and where human populations are denser also have more alien species, but these effects are stronger for islands.” These factors increase the likelihood of humans introducing many new species to an area. This results in the destruction of natural habitats, which in turn allows non-indigenous species to spread. Islands and coastal regions seem to be particularly vulnerable because they occupy leading roles in global overseas trade.
“Hawaii and New Zealand lead the field for all examined groups”, explains participating ecologist Dr Franz Essl from the University of Vienna: “Both regions are remote islands that used to be very isolated, lacking some groups of organisms altogether - such as mammals, for instance. Today, both regions are economically highly developed countries that maintain intense trade relationships. These have a huge impact on the introduction and naturalisation of non-indigenous species”.
The presence of large numbers of alien species across many regions of the earth comes with serious consequences, especially in cases where indigenous species are driven out and natural habitats are changed. This is very problematic with regard to islands since many indigenous species tend to exist only on the island itself and are therefore particularly vulnerable to the threat of alien invaders. "Islands, such as New Zealand and Hawaii, are often geographically isolated and have, in evolutionary terms, unique flora and faunas, which were not at all prepared for the most diverse types of entrained species," explains the ecologist Marten Winter of iDiv. Various laws and treaties designed to reduce the spread of alien species have been passed around the globe. "That is precisely the reason the Cross-border cooperation in Europe, which has now begun with the EU regulation on invasive species, is important and necessary," says Winter. New Zealand has already passed comprehensive legislation designed to prevent the introduction of further alien species over the past few years. And on some smaller islands, alien predators such as rats or mice have been successfully eliminated. These examples show that it is possible to take successful action.
W. Dawson, D. Moser, M. van Kleunen, H. Kreft, J. Pergl, P. Pyšek, M. Winter, B. Lenzner, T. Blackburn, E. Dyer, P. Cassey, S. Scrivens, E. Economo, B. Guénard, C. Capinha, H. Seebens, P. Garcia-Diaz, W. Nentwig, E. Garcia-Berthou, C. Casal, N. Mandrák, P. Fuller, C. Meyer, and F. Essl (2017): Global hotspots and correlates of alien species richness across taxonomic groups. Nature Ecology and Evolution. DOI: s41559-017-0186
The study was supported by the European Commission (COST Action TD1209), the German Science Foundation (DFG), the Volkswagen Foundation through a Freigeist Fellowship and others.
Press release of Durham University: https://www.dur.ac.uk/news/newsitem/?itemno=31655
Global Naturalized Alien Flora (GloNAF) https://glonaf.org/
Dr Wayne Dawson
Durham University’s Department of Biosciences
Dr Franz Essl
University of Vienna
Dr Marten Winter, Dr Carsten Meyer
German Centre for Integrative Biodiversity Research (iDiv) and Leipzig University
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Mag. Alexandra Frey
University of Vienna
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iDiv Media and Communications
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