It is almost a basic assumption of conservation biology that introducing exotic plant or animal species in a landscape degrades that landscape’s biodiversity value. The justification I have always accepted is that introducing new species without pre-existing predator-prey relationships can lead to ecological instabilities that drive certain species to extinction and reduce biodiversity values. The endpoint is potentially greater homogeneity and a sensible application of the Precautionary Principle – suggests not disturbing such equilibria. Recently there have been suggestions that this argument amounts effectively to a type of ‘species racism’ that says in effect – hold it right there – the pre-existing gene pool mix should not be tampered with. Applied to new human races setting up in an established society of different race this would be understood to be racism.
It isn’t a new type of argument – the link provides several precursor articles – but I also recall the views of Julian Simon in the 1970s who suggested biodiversity values were increasing in the US because of the introduction of feral species. In Australia feral species of birds dominate our urban landscapes and, although the number of extant species has barely changed, the range of many native species has contracted enormously. The situation with respect to Australian mammals is much worse – here species numbers have contracted dramatically and there have been numerous extinctions. Obviously then introduction of the cane toad, honeybee, rabbit, rat, feral cat and fox have been disastrous for Australian wildlife. Tim Low has written on such matters in a comprehensive way.
The argument that introducing ferals should not necessarily be considered a problem has one point of validity – eliminating feral species is so difficult that in many cases we do need to just learn to live with them. Moreover it is true that there is very little evidence on the impacts of invertebrates.
Generally however I reject these arguments. There are many situations where we can promote the survival prospects of native species and should do so – many natural landscapes can be regenerated. The arguments have been picked up in the type of ‘culture wars’ nonsense promoted on right-wing blogsites. The claim is that hostility to ferals is equivalent to not recognising human roles in natural environments. My reading of the conservation biology literature is that is almost never the case. One of the right-wing nutters that I came across recently suggested that ferals replacing local species was just Darwinian evolution working and the fact that it was occurring in Australia reflected the derivative, feeble character of Australian biodiversity. This was exactly the argument used by the acclimatisation societies when they established a range of exotic species in Australia. Subsequent developments in phylogeny showed these claims to be totally wrong – Australia has some of the most distinctive flora and fauna on the planet. (97)