We have all heard stories in the past about how invasive species have travelled along transport networks or have managed to hitch a ride from one country to the next. For example: Japanese Knotweed has spread rapidly down road and rail networks in both the UK and USA. Zebra Mussels have been transported around North America by ships ballast water.
Well a new study (Tatem & Hay, 2007) published in Proceedings of the Royal Society B: Biological Sciences (open access) has now analysed the global structure of the worldwide airline transportation network (WAN) and highlighted the potential risk of deliberate or accidental movements of climatically sensitive organisms around the world. Tatem & Hay (2007) analysed over 3 million flights along over 3500 WAN flight routes. Using the logic that a species is likely to be a threat to a region that has a similar climate as the place the species originated from, they identified hotspots (N USA, Caribbean, central W Europe, Scandinavia and E Asia) that are at risk from introductions of non-native species. In addition, they discovered that more flights occur during July and August, at the time when the climates of different regions align themselves, therefore increasing the chances of non-native introductions.
Tatem & Hay (2007) conclude their article by stating that “organisms have never had a better chance at expanding their ranges”. With the current climate change scenario looming over us, is this in fact a problem? This process will facilitate range expansion far quicker than species themselves can manage. This is a subject that is open to much debate. I personally think that there is a problem here due solely from a biosecurity perspective (i.e. potential for increased disease & pest distribution) that requires addressing by international legislation.
Ref: Tatem, A.J. & Hay, S.I. (2007) Climatic similarity and biological exchange in the worldwide airline transportation network, Proceedings of the Royal Society B: Biological Sciences Online early (DOI: 10.1098/rspb.2007.0148)
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