The Role of Warfare in Promoting the Introduction and Invasion of Alien Species

James P.H. Paterson
Peter Jebsens veg 61
5265 Ytre Arna
Bergen
Norway
Email: pollocp@online.no

Associations between the spread of alien species and human influenced disturbance are well documented (e.g. Kowarik 1995, Crawley 1987). Warfare is a significant example of anthropomorphic disturbance, creating huge upheavals of soils, forests and urban areas due to bombing campaigns and clearance for runways etc. The logistics involved in any military action provides the perfect opportunity and means for the transportation of alien species. The movement of troops, weaponry and foodstuffs including live animals, require that either inadvertently or deliberately alien species are introduced.

Probably the most far reaching of military campaigns in terms of its impact on the spread of alien species was the World War II. This conflict literally spanned the globe from Europe, the African subcontinent and the Atlantic islands to Asia and the Pacific islands. The influence of World War II on the spread of alien species was due mainly to the large numbers of vehicles used in this war and the support equipment required to keep the war machine running. These were undoubtedly responsible for the introduction and spread of numerous land and aquatic aliens. 

There are several documented and anecdotal references to species introductions during World War II. Binggeli & Starmer (1997) reported that the introduction of the common house mouse (Mus musculus) to Pitcairn Island in the Pacific was due to their being transported inadvertently in cases carrying radio equipment. Surely this cannot be an isolated example as these ships carrying military equipment may have had further or previous ports of call and the possibilities for spreading mice throughout Polynesia are staggering. Another example of accidental introduction is that of the brown tree snake (Boiga irregularis) on Guam (Fritts & Perry 1997). This species was accidentally introduced to Guam towards the end of the war and has been responsible for the extirpation of nine of Guam’s thirteen forest bird species. The German wasp (Vespula germanica) entered New Zealand in cases of parts for aeroplanes (Fordham 1961) and is now found in much of New Zealand (Donovan 1998). The Triffid or Siam weed (Chromolaena odorata) was accidentally spread to a number of locations around Asia and the Pacific (Cruttwell McFadyen 1989). This shrub also found its way to South Africa as seeds in fodder and is now probably the number one terrestrial weed on the eastern seaboard of South Africa (Boon pers. comm. 2000). 

Alm et al. (2000a), linked localities of Phyteuma spicatum and P. nigrum in the north of Norway with World War II military campsites used during the German occupation of Norway. Alm et al (2000a) proposed that this is due to the importation of fodder crops, possibly from central Europe for German horses and the subsequent establishment of these species. These stands and those of Pimpinella major, another species suspected of being spread by German fodder (Alm et al. 2000b), are the northernmost record for these species and are still in existence after 55 years.
	
Other deliberate introductions of species are also documented, for example it is widely believed that the Japanese Imperial Army was responsible for spreading the Giant African Snail (Achatina fulica) throughout the Pacific area during World War II as a food for the troops (Lever 1994, Johnson & Johnson 1956). The Japanese are also attributed with the deliberate introduction of Leucaena leucocephala as a camouflage plant on Pacific islands (Shidei 1974). The Rhinoceros Beetle (Oryctes rhinoceros), a serious pest of coconut (Coco nucifera) and other palms was introduced to Papua New Guinea during the same period (Liebregts pers. comm. 2000).

A very clear example of an intentional introduction of aliens by the military can be found in the Puget Sound area of the USA. Here the military planted gorse (Ulex europaeus) at the start of World War II in order to protect gun placements from attacks (Edain pers. comm. 2000). The mesquite (Prosopis juliflora) has invaded Ascension Island and this has been reliably traced to the use of this island as a stop over site en route to the Falkland Islands. It is thought to have been deliberately introduced into military gardens during the Falklands conflict (Baskin pers. comm. 2000).

The deliberate introduction of species as a source of food, for human or animal consumption during warfare is not solely a problem of the 20th century. Captain David Porter of the US frigate Essex during the war with Britain in 1813 wrote:
‘I generally took with me seeds of different descriptions, with which I was provided, such as melons, pumpkins, peas, beans, oranges, limes &c. together with peach stones, wheat and Indian corn, which were planted within the enclosures, in the most suitable places for them, and the natives always assisting in pulling up the weeds and clearing the ground for planting. The nature of the different kinds of vegetables and fruit that each kind of grain would produce was explained to them and they all promised to take the utmost care of them and prevent the hogs from doing them any injury’ (Porter 1986).

In his paper on the effects of war on the flora of Micronesia during and immediately after World War II, Fosberg (1953) suggested that transport in large numbers and various forms gave an opportunity for wide expansion of aliens throughout Micronesia. He further stated that the effects of war and subsequent movements of troops and equipment have offered the greatest opportunity to pioneer species since the islands of Micronesia emerged from the sea.
	
In Europe, the spread of the alien Buddleja davidii has been linked to the blitz of London and other major cities of the United Kingdom during World War II (Paterson 2000). This species evolved on dry scree slopes in China (Crawley 1989) and was subsequently well adapted to colonise the vast areas of rubble created by the destruction of thousands of homes and spread rapidly throughout these areas (Owen & Whiteway 1980). The spread of Robinia pseudoacacia in Berlin (Kowarik 1995) and Prunus serotina throughout Germany (Starfinger 1997) are directly attributable to disturbances caused by World War II. The former being due to the allied bombing campaign creating waste areas, and spread of the latter was aided by deforestation during and after the war.
	
Duffner and Wathern (1988) concluded that the destruction of railway stations and loading areas during World War II led directly to the development of a rich alien flora within the confines of these areas, many of which have remained untouched since that time. These areas have subsequently taken on somewhat of a nature reserve status.
	
In conclusion, it is with certainty that warfare has had, and continues to have, a dramatic and substantial influence on the spread of alien species throughout the globe. Such influence can, as previously stated, be directly in the form of deliberate introductions, or indirectly as transport of animals, seed or vegetative materials with or on equipment. It is also important to note that alien species, present in small numbers may have the ability to take advantage of the disturbance of soils or forested areas caused by military actions. For example the disturbances caused by the usage of large-scale herbicide applications in the form of Agent Orange, and similar herbicides, designed to reduce cover for communist sympathisers in the Vietnam War were directly responsible for the loss of 23% of native forests and for the rapid increase of bamboo species that rapidly colonised these severely disturbed areas (Nguyen 1997).
	
The most recent conflicts in area such as the Falklands, Korea, Vietnam and the Middle East have certainly compounded the effects of the World War II on the distribution of alien species by creating a new era of disturbance and invasions. 
References

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