Native vs. non-native (was Re: all theory thread DESIGN PRINCIPLES).

mangodance bmn at iglou.com
Wed Aug 30 23:55:54 EDT 2000


Toby Hemenway wrote:
> We're in agreement that invasive plants plus stupid management, or
> over-exploitation, is a recipe for disaster. Intelligent management can
> reduce invasives. I've seen Scotch broom and Himalayan blackberry, two
> rampant invasives here in the NW, reduced to insignificance in just a few
> years once people stop clearing for pastures. That allows a canopy to form,
> shading out the invaders. I could list many other examples, but that's what
> I mean by equilibrating: the invasives become restricted to small patches,
> even if they don't disappear.

Maybe.  It does depend on the invader.

> >> [some plants are] branded as invasive because they interfere
> >>with humans' use of
> >> an area, by displacing cattle forage or farmland.

> > Can you support this?
> 
> You bet. Here's a quote from "Impacts of Introduced Species in the United
> States" by Daniel Simberloff, a fairly famous biologist writing in
> Consequences journal, from a website whose URL I've lost (I have the file,
> though): "Best documented are [exotics'] costs to agriculture: about a
> fourth of this country's agricultural gross national product is lost each
> year to foreign plant pests and the costs of controlling them." He mentions
> that "Leafy spurge, an unpalatable European plant that has invaded western
> rangelands, caused losses of $110 million in 1990 alone." The literature is
> full of statements like this, with no mention of inappropriate land use as
> the real cause.

...and no causation for listing as an invasive/noxious due to
ag...at least in the quote.


> > The problem with Kudzu is not that it restores cleared land to
> > forest.  It is quite the opposite.  It can handily exploit such
> > cleared areas but eventually get into forests and turn them into
> > graveyards.
> 
> My observation of kudzu in Georgia and South Carolina was that it uses road
> margins, abandoned fields, and other deliberate clearings to enter small and
> fragmented forest patches that have plenty of human-made edge and thus are
> lighted deep into the interior. It seemed not to do well in larger, darker
> forests. Again, bad land management coupled with an opportunistic species is
> a disaster. I'd ask why it hasn't taken over Japan.

These are usually areas in which it was originally planted or is
able to get a start.  The forests need not be fragmented.  It can
do that well enough for itself.   One person working it on land
consistently can probably manage a small plot.  What happens when
they're gone?  Japan has a different climate and a variety of
uses for this plant and harvest it in large quantities.

> Most of the southeast is 2nd (or later) growth forest, farm, or drained
> wetland; little is undisturbed, hence its susceptibility. You have a point
> with Hawaii, although a lot of the trouble there is with animals, less so
> with plants. 

Hawaii has a huge problem with invasive plants.  

> And islands have species in proportion to the logarithm of
> their land area (an exponential drop as islands get smaller), and have no
> way to replenish local stocks, so they are far more sensitive to disturbance
> than continents. Also, since much of Hawaii was cleared for farming, many
> exotics got a good hold there for launching into the forest margins. Again,
> short-sighted land use. I stand by my statement, with its restrictions. In
> old-growth I only see invasives at road cuts. They need sun.

Many of the areas under attack in Hawaii are extremely steep,
very rugged and remote.  However, the initial statements had to
do with the use of invasives, rehab of land, and what is native. 
Old growth is a different beast altogether.


> >
> >[Holmgren's recombinant ecologies are]
> > an issue of rehabilitation and not restoration.
> 
> To me that distinction seems arbitrary (but I'm not a pro). For example,
> when David Wingate used N-fixing, non-native casuarina on Nonesuch Island to
> nurse the return of a native cedar forest, allowing native birds to return,
> was that rehab or resto? The replanted cedars didn't survive on their own,
> so he jump-started the forest with exotics, then took them out. I suspect
> most successful restorations involve rehab.

Depending on who weilds the terms, it *can be* arbitrary.  Even
the Ecological Restoration Society misuses "restoration" (as do
many in my own agency).  Preservation, restoration, and rehab, 
are on a continuum.  The first is obvious.  The difference
between restoration and rehabilitation is mainly one of purpose. 
Rehabilitation takes damaged areas and rebuilds them to establish
some function or condition other than its original state.  A
rehab might take a brownfield area in a city and create a soccer
field, or take a field of fescue and create drainage areas and
wetlands.  Restoration entails takes them back to an original
condition in structure and function.  A general example might be
turning prior converted farmlands back into wetlands.

> I don't think that's what Holmgren means, but I'll avoid speaking for him;
> he's been on this list. For me, it makes sense to rapidly restore the health
> of the soil and attract a diverse fauna via fast-growing non-natives
> (especially if they're already there; I believe that's what David was
> referring to, and as examples to learn from). These plants then can later be
> overtaken either by better-adapted natives (since conditions favor them
> again), or by human-useful exotics. Used intelligently, these weedscapes are
> self-destructing, like most pioneers. It's using biology rather than
> engineering. The alternative, from what I've seen of restoration (forgive me
> if I'm oversimplifying), is herbicides, huge amounts of human and machine
> labor, and frequent replanting (I'm told herbicide makers often fund
> restoration projects; they like repeat customers). Not to sound smug, but
> that sounds like the classic "thoughtless and protracted labor" as opposed
> to Holmgren's "thoughtful and protracted observation." If we can't eliminate
> the conditions that attract invasives--large clearings, low fertility,
> etc--they'll just come right back.

I would still point out that invasives don't need clearings, low
fertility, etc.  They manage to get into healthy communities and
impact them.  I would agree unfortunately that there is a great
deal of herbicides and such used by folks who may mean well, but
have singular focus.  I've been at odds on our own agencies
projects, and those we partner on.  Often times, when the final
word comes down, people do it because they are strapped for
labor/money and it's a cheap way to knock back the competition. 
Unfortunately, one example of where this falls apart is wetlands,
riparian areas, and basins.  Little regard is given to non-target
impacts.  But comparing a thoughtful system to a poorly
conceived/performed process isn't quite a fair comparison.  It
seems to me that if Permaculture is about less
maintenance/efficient labor, we shouldn't be advocating a system
where you will most probably have to readdress one's plantings
because one used aggressive exotics.  In addition, I still think
that since we aren't static, why should we not plan for the time
when we are no more, or those who come after us?

> I think the nameless mangodance and I are in basic agreement about
> goals--curtailing species loss, reducing human impact, enhancing
> biodiversity--but we differ on methods. I find fast-growing non-natives an
> important tool in disturbed landscapes for achieving those goals. But as
> Mollison says, let's stay the hell out of the bush.

Sorry... I'm Barry Nichols.  I'd say that was accurate.  But I
see the use of the exotics more as an easy tool rather than one
that is needed.  It also requires attention later, or possibly a
disregard for what comes after us.  I do have a couple of issues
I struggle with when looking at cultivars vs. wild types.  I'll
bring that up in a separate thread though.  
-- 
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