Subject: Invasive non native species

From: "Bareis, Santa Cruz" <[email-masked]>
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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From: "Naomi Rea" <[email-masked]>
Date: Tue, 21 Oct 1997 10:38:51 +0930

ditto to message from Santa Cruz and G'day from Australia

The concept of highly productive, concentrated, low energy PC systems 
(food bowls) is admirable and attainable. However, the SCruz message 
a timely reminder about bumping up diversity with introduced 
non-native species.  Invasives are changing the floristic identity of 
ecosystems and countries.  Horticulture and spp introductions have 
alot to answer for.  Of 463 exotic pastures introducted to Northern 
Australia, only 5% had a potential use, 13% became weeds and < 1% 
were both useful and not weeds (Lonsdale 1994 Aust J. Ecol). 

Native plants have taken squillions of years to evolve superb 
adaptations and strategies. Can humans really hope to do better ?
Concepts such as ecosystem mimicry, landscape engineering and 
PC are laudable ideas for a planet facing food shortages, massive 
ecological change, rehabilitation of degraded environments and  and 
in need of a new social ethic ... but, am wondering if PC really is 
low energy ?  The native garden with bush foods, medicine, materials 
and fuel would have to be the ultimate low energy system.  Albeit, a 
PC-bush garden may not be as productive as a PC-everything system, 
but it is ecologically safe and long term.  Listening, looking and 
learning from natural systems, refined over centuries, may be easier 
than struggling to do better

Naomi

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From: "Naomi Rea" <[email-masked]>
Date: Tue, 21 Oct 1997 10:38:51 +0930

Naomi