permaculture

[Heide Hermary <heidehermary@pacificcoast.net>]

At the IFOAM conference just recently one of the speakers mentioned in 
passing that 90% of the earth's potable water is tied up in living 
organisms.  I don't know where that info comes from, but it goes a long 
way towards explaining desertification when species are eradicated 
through pesticides, overgrazing, clearcutting, etc.etc.

As for trees pumping water: not really. A better picture (simplistic, I 
know) is to visualize the tree as a huge straw, with water literally 
sucked through it via evaporation through the stomata which are open for 
photosynthesis. When water supply is low, stomata close, and 
photosynthesis stops also (C4 plants do this somewhat differently...). 
Basically what I tried to say before: bare soil will evaporate a huge 
amount of water.  From my observations in this ecosystem here trees 
actually preserve soil water.   I am sure a tall grass prairie will 
function similarly, but an overgrazed one will act more like an 
ornamental lawn.

Heide

Kirby Fry wrote:

> Hello Ute,
>
> > > There are situations where trees are undesirable because of their
> 'pumping' action.  <<
>
> I didn't necessarily pick up that the birch's pumping action, and
> consequently lowering the water level of the bogs, is inherently a bad
> thing.  Can you qualify a bit why it's detrimental?
>
> > > The slightly drier conditions resulting from this drainage favor the
> establishment of (typically) birch trees which are opportunists when it
> comes to water supply.  <<
>
> So before the drains were put in the birch didn't stand a chance, and now
> with the drains in place the birch are moving in?  It sounds like to me that
> if conditions have been created where the birch can grow then they should be
> allowed to do so.  Otherwise, we are trying to maintain a system that no
> longer suits the topography.
>
> > > Restoration measures for such peatlands include the removal of the birch
> trees and the blocking of drains.  <<
>
> If the drains were blocked and original bog conditions restored then birch
> removal seems slightly more appropriate.  However, I bet a lot of trees are
> cleared where the drains are not blocked, and original bog conditions are
> not restored.  Once again we end up pitting ourselves against what nature
> chooses to fill an ecological niche with.
>
> > > There are also situations where non-native trees can cause damage, such
> as eucalyptus plantations in arid regions where they compete with native
> vegetation for water.  <<
>
> I'm not necessarily fond of the eucalyptus tree, myself, as it's way
> overused in international forestry and extremely flammable.  However, just
> about everything on this planet competes for water.  There has got to be
> better grounds for eradicating a species than whether or not it's native and
> requires water to live.
>
> > > I guess one has to try and get quite detailed information on the local
> ecology and ecosystems and/or observe natural ecosystems well, before one
> can judge whether certain trees are beneficial or not in a given situation.
> <<
>
> Well, just label me an extremist, but I'm still not convinced that tree
> removal is the solution for the scenarios you described.  Thanks for
> relating the story, Ute.
>
> Kirby
>
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