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  • From: Rain Tenaqiya <raincascadia@yahoo.com>
  • To: permaculture@lists.ibiblio.org
  • Subject: [permaculture] invasives and disturbance
  • Date: Thu, 30 Dec 2004 23:33:11 -0800 (PST)

While I sympathize with much of what Toby is saying, I feel like I need to
remind everyone that disturbance is an essential part of wild ecosystems.
Humuns are not the only source of disturbances, and most ecosystems have some
cataclysmic disturbance at least every few hundred years. When an invasive
exotic species is introduced into a relatively undisturbed ecosystem, it may
not displace many individuals of native species at first. But once there is
a disturbance, whatever its source, the invasive exotic may outcompete or
overeat the natives in the new succession. Ecosystems are chaotic systems
which are sensitive to initial conditions. When an exotic species is
introduced, the initial conditions change which means the 'climax' ecosystem
may be radically different from the one before. Examples I've witnessed:

1. Undisturbed California coastal scrub next to a line of blue gum
eucalyptus trees slumps, opening the soil to colonization by eucalpytus
seeds, ultimately resulting in a forest ecosystem.

2. Relatively pure native California bunchgrass meadow disturbed by vehicle
tracks and swale building recolonized by exotic annuals.

Everything gardens and invasive exotic species are no exception. Introducing
them even to relatively undisturbed ecosystems can radically change those
ecosystems, especially when we consider the timescales over which
evolutionary change occurs. In order to allow for the free
self-determination of other species, and to conserve biodiversity, we should
be careful about moving plants from one ecosystem to another. This does not
mean supporting Monsanto's drive to co-opt ecological concerns in order to
maximize its sales of Roundup by demonizing exotic plants. (If we want to do
this, we can start by poisoning all the people of exotic ancestry that stole
the Americas and Australia from the 'natives.')

Rain



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