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Feral species & conservation values

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.

This article questions the view that we should be concerned about the introduction of new species.

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.

4 comments to Feral species & conservation values

  • Mel

    “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.”

    I’ve heard similar arguments many times, Harry, by right wingers who know absolutely nothing about ecology. The argument is silly because plants and animals co-evolve with other biota. Accordingly, the indigenous grey box and iron barks in my paddocks are a thriving community of life including various soil organisms, invertebrates, birds and mammals (I have sugar gliders). Most of these indigenous trees have chewed leaves, lerps, galls etc etc.. On the other hand, the introduced weed species do not have a suite of diseases and predators to keep them in check or to tie them into the food chain. Many are untouched ecological deserts. Generally speaking a level playing field does not exist and the weeds, unhindered by pests, reduce biodiversity.

    Obviously there are always exceptions to the rule and some “weed species” are now valuable habitat and/or food for indigenous beasties. In some places blackberry bushes provide valuable habitat and protection from foxes and cats for some small marsupials, for instance. I also note small seed eating indigenous birds at my place love wire-weed seeds, so I leave these alone.

  • conrad

    “I have sugar gliders”

    I’m jealous. How about I trade a few brushtails and we introduce them to Melbourne?

  • hc

    I think there are sugar gliders quite close to Melbourne – in Yarra Ranges for sure.

  • Mel

    Sugar gliders are very common in central Victoria. All three of my nesting boxes are being used by sugar gliders, however I would prefer to attract the much rarer brush tailed phascogale. I’ll put up more nesting boxes and hopefully one will turn up sooner or later- they have been seen along my road.

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