Alien Species.vp - IUCN

From ecology to politics: the human side of
alien invasions
Tim Low
Abstract
People are animals. Animals often help disperse other species. People were dispersing
other species many thousands of years ago, with dramatic consequences. As human
ecology changed, the rate of dispersal has multiplied. Where once humans were nomadic,
moving between resource patches, now they are sedentary, resources flowing to them on
vast transport networks. Alien invaders hitch on the highways. Disturbance to environments
often helps them. The values we hold also help them. We exalt mobility, freedom,
speed, diversity, progress and familiarity, and view nature mechanistically. The political
trend towards globalisation also helps them, for it also exalts mobility, promoting the
movement of products and therefore movement of pests, since we cannot devise transport
systems that exclude them. At the same time, governments are also losing power to regulate
the flow of products. The threat posed by pests is greatly underestimated by almost
everyone, including environmentalists. We face an irreconcilable dilemma. We want a
world in which people and products are free to move, but other species are not. To help
reconcile this dilemma, we could apply cost-benefit analyses to trade and travel to show
their true cost, and tax them accordingly. We should change the way we perceive living
things, acknowledging the pest threat.
Introduction
The past informs the future. This paper draws upon the past to see where we are heading today,
touching upon ecology, history, politics and values. Affluent English-speaking countries are
the main focus, with several examples drawn from Australia, the author’s home country.
Early history
People are animals. Animals disperse seeds when they carry them in their fur (or clothing) or
eat fruits and drop the seeds elsewhere. By spreading seeds, animals can expand their food
base. After Krakatau erupted in 1883, birds brought seeds to the barren volcano. Twenty-four
fig species (Ficus spp.) now grow on the island, along with many other fruit-bearing plants,
supporting 23 species of fruit-eating bird and bat (Thornton, Compton and Wilson, 1996).
Fruit-eating animals could not live on the islands today had their forebears not brought seeds.
Homo sapiens operates in a like way. Nomadic cultures spread seeds. Groves of wild fruit
trees in northern Australia signal old Aboriginal campsites (Hynes and Chase, 1982). Desert
tomatoes (Solanum chippendalei) were spread outside their original range when Aborigines in
the 1970s took their fruits south in cars and scattered the seeds (Peterson, 1979). Humans
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