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permaculture - Invasive non native species

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Chronological Thread  
  • From: "Bareis, Santa Cruz" <ibabambu@cruzio.com>
  • To: "Permaculture list" <permaculture@listserv.oit.unc.edu>, <BAMBOO@HOUSING.UCSC.EDU>
  • Subject: Invasive non native species
  • Date: Mon, 20 Oct 1997 09:31:53 -0700

Ref; Potential Invasiveness

During a recent trip to Southwest China we were traveling with a group of
Chinese botantists -the subject of non-native plants came up into the
conversation, -in that area apart from the ubiquitous ecalyptus plantations
there were surprizingly few introduced plants in the landscape. To our
surprize the story of an invasive non-native Eupytorium sp. originally from
Central America, and how it has been estimated to have invaded fully 30% of
the tillable land in sub-tropical China. This particular weed is so toxic
that even goats won't touch it! And more labor is spent each year in
trying to eradicate Eupytorium than in re-forrestation efforts.

We all have corollaries to the Eupatorium in South China, invasive plants
that have escaped horticultural boundaries into our landscape and are
creating havoc with farming. Basically the problem appears that as
bio-diversity is changed through introduction of non-native species the
potential that some percentage of the introduced horticultural plants
become naturalized and begin to expand their foothold.

Regions with mild climates seem the most at risk to non-native species,
and recently regional environmental planners have begun to site the
problems of maintaining natural plant communities into the future. Also
habitat destruction by invading species makes it necessary to enter fragile
areas to try to separate and eradicate non-native plants. The fact that
the invasive issue has not taken center stage is that many of the species
are or were originally interesting horticultural species. Here in Central
Coastal California the list of non-native invasive species now outnumbers
the native forest and grassland species!

The subject is further complicated when we consider the invasive potential
of non-native fungus spore. Phytothera genus fungus spore are a huge
problem in nursery soils. Now escaped this non-native spore has destroyed
the magnificent Chamycyparis lawsontonia (Port Orford Cedars) and on the
East Coast the fungus Discula destructiva, threatens the Cornus florida,
eastern dogwoods. These invasions were driven by horticultural plantings
of non native species and we as plant lovers should be aware that this
whole historical example which is playing out in our own forests has
occured before, European native forests were harvested and depleated by
fungal blight before Elizabeth I, sent Raleigh to the new world in search
of new and different plant species to "renew the forests".

Perhaps as we expand our own collections of rare and different plants we
should be aware of the incredibly complicated and slow moving process that
we are setting into motion. Planting trees and bamboo increases the
intellectual interaction between ourselves and the natural world but to
begin to recreate the complexity of healthy environments we need to see
beyond the quick returns of agro-forestry; towards ways to stabilize
healthy forests with natural diversity.

There is a direction in the permaculture and new horticulture movements
recently. The ideal of planting a tree or bamboo that grows fast enough so
that we can not only enjoy it's shade but harvest its wood for "expanded
productivity". The idea that we can introduce fast growing "productive"
species must be balanced by the potential that some of these species in
some regions WILL produce unwanted results, as their aggressive traits
escape beyond intended boundaries.









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