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  • From: Bob Howard <rmhoward@omninet.net.au>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Are we a weed?
  • Date: Thu, 27 Mar 2003 20:40:04 +0800



Toby Hemenway wrote:

> I was interested in the possibility that one-way weed travel is just a
> myth, since people have cited a few counter-examples (though the examples
> are mostly of animals, which have very different dispersal systems than
> plants). I pulled down my copy of Ecological Imperialism: The Biological
> Expansion of Europe, by Alfred Crosby, and browsed around. He cites data
> showing that of 500 farmland weeds (plants) in the US, over half are from
> Europe, and in Canada, over 60% are European. Roughly the same numbers are
> found in Australia and S. America. But in Europe, less than 10% of the
> weeds are not from Europe or Asia. Not a single Australian or NZ weed was
> found in Europe until after 1920. The only major weeds in Europe from North
> America are two fleabanes, Canadian waterweed, and a handful of others.
> Most of the most aggressive US weeds, like ragweed, goldenrod, and
> milkweed, haven't gained a foothold in Europe. Yet roughly the same amount
> of shipping goes to Europe as from it, s!
o you'd
> think just as many species have been imported both ways.

Toby
I agree with your point about guilds further down. The "before 1920" date is
pretty significant for Australia. Many environmental weeds in Australia are
garden escapes or deliberate releases. In Australia, in the 19th Century
there was a naturalization movment that sought to introduce deliberately
european plants and animals into Australia. The fox and the rabbit were both
deliberate introductions as well as many plants.

The reason there are no australian weeds in Europe is emphatically that the
traffic has all been one way. Not that tehre is any intrinsic virtue or
virulence to the european variety. In australia some of the most destructive
environmental weeds are from other parts of australia. Plants such as acacia
saligna and hakea suavolens to name but two.The latter is a declared weed in
south africa where it has become established in the wild as have a number of
australian acacia species which have been deliberately introduced into
Africa..
Again get over this obsession that there is something intrinsically virulent
or virtuous about Europe. It's total garbage.

Bob Howard



>
> Thus the (mostly) one-way weed establishment is a fact. One reason for
> this, in addition to those I cited in my last post, is that
> counter-directional species usually travel alone, separate from their
> guilds, while European weeds travel with their guilds: We bring cattle,
> sheep, and all the other animals that have adapted with Euro-weeds (which
> have burrs adapted for our livestock, pass through their guts unharmed,
> etc); we bring pollinators by the millions (European honey-bees love
> Euro-weeds), and we bring many of the other insect and plant associates
> that are allies of the weeds. That broad-band traffic doesn't go the other
> way, and thus non-Euro-weeds don't thrive. You could say they die of
> loneliness.
>
> Toby
> _____________________________________________
> For a look at my book on ecological gardening,
> Gaia's Garden: A Guide to Home-Scale Permaculture, visit
> http://www.chelseagreen.com/Garden/GaiasGarden.htm
>
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