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Aliens and invasives threaten native biodiversity

• Message 1. 

  Posted by Andricus (U12229961) on Friday, 6th June 2008

  I found it very disconcerting to see a presenter on Gardeners World to take enjoyment from garden escapees. Biological invasions are widely seen as the greatest threat to native biodiversity possibly, at a global scale, after habitat destruction (e.g. deforestation). Workers in invasion ecology distinguish between invasive species as established invaders that are detrimental to native biodiversity, and alien species, which have established but apparently cause no damage. Most of the species shown in the program would probably be regarded as aliens, although the Hottentot fig (Carpobrotus edulis) that was also shown, is well known to exclude native species for instance on the cliffs in Cornwall by swamping.
  However, another well known phenomenon among invaders is a lag period when species establish but do not spread at a significant rate, i.e. they are aliens. It is thought that during this period the species adapt to local conditions before other ecological factors, like the lack of natural enemies, allows such species to spread explosively and to become invasive. Lag periods might take years, decades or centuries and most likely not all alien species will turn invasive at any time. E.O. Wilson named biological invasions among the riders of the apocalypse in the context of biodiversity loss, and gardening certainly since victorian time has been and still is one of the main motivations to move plant species between regions and continents.
  I would have wished a program like Gardeners World would be educational about the possible consequences of gardening activities rather than celebrate what I would regard as the downside of gardening, i.e. escapees....
  

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• Message 2

  , in reply to message 1.

  Posted by Ariadne Knickerbocker (U4534559) on Friday, 6th June 2008

  Eh?

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• Message 3

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  Posted by Brummie_gardener (U11880671) on Friday, 6th June 2008

  Andricus, I totally agree with you. I really think more people should be aware of the problem.
  For example, how many people bring a few seeds or cuttings wrapped up in their suitcase when they go on holiday, without thinking how the plant might affect a new area or what pests and diseases they might be introducing?
  Why the fear over GM plants escaping from farmer's fields but not alien species escaping from gardens?

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• Message 4

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  Posted by MsSeahorse (U11657392) on Friday, 6th June 2008

  Doesn't this have huge implications for the plant swap at the NEC next weekend? Just think, 5000 innocent Cosmos could unleash The Day of the Triffids all over again!

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• Message 5

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  Posted by janerowena (U10782401) on Saturday, 7th June 2008

  Does it really matter?
  
  Compare it to the human species, who are rearranged and redistributed all over the world. Cornwall would not be half as pretty without it's fuchsia hedges and banks of montbretia. There are british natives all over New Zealand and India and the USA, to name but a few. Why should a hottentot fig not grow where nothing else will?
  
  Yes, there are some things such as himalayan balsam and japanese knotweed that are pests, but I would rather see a riverbank of himalayan balsam than a field of marestail anyday. Plant species, animal species, humans - we are all constantly changing and adapting to new growing conditions.
  
  I rather like it. And if there was ever a lobby to support, say, red ants from near-extinction, I would definitely not support it.

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• Message 6

  , in reply to message 5.

  Posted by catchrisls (U10291326) on Wednesday, 11th June 2008

  In reply to message 5: Yes it does matter.
  The five major threats for biological diversity on our planet are habitat destruction, habitat fragmentation, over-exploitation, pollution and invasive alien species. It is therefore important that we protect our native species.
  
  If we lose just one native, be it plant, insect or whatever, that is important to the survival of other native species, then we start a chain reaction that is difficult to stop or even reverse. A programme such as GW should highlight this issue and educate rather than glorify it.
  
  As regards to your comment about red ants, please see
  
  Myrmica sabuleti ( a type of red ant) is important to the survival of the large blue butterfly. It was also covered in Richard Attenborough's 'Life in the Undergrowth' (series 4)

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• Message 7

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  Posted by janerowena (U10782401) on Wednesday, 11th June 2008

  Well, that would explain why there are so many large blues where I live - we are near heathland and very short rabbit-cropped grass.
  
  However, much as I love large blues, I also love many other species from all over the world and don't feel that I have to fiercely guard the species that live here.
  
  Whilst living in the Weald of Kent I regularly saw wild boar and parrots. Minks were in the streams, and here it is foreign crayfish that are the naturalists bugbear. The locals, on the other hand, love them and they are easily caught. I can't say I'm all that happy with so many rabbits around, but they are what is keeping the grass short for the red ants that feed the large blue.
  
  There are probably quite a few people out there who, for the sake of glimpsing a large blue perhaps twice in a summer if they are lucky, would rather lose the rabbits and the red ants.

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