permaculture

[Toby Hemenway <hemenway@jeffnet.org>]

Marshall wrote:

> Toby, why do you accept such a unsustainable idea as that pinon/juniper
> offers much greater food potential than grass.

What I described was "an agriculture based on a multi-crop sustainable
harvest of food, forage, and timber from P/J forests." Ben Haggard also
included pine nuts, acorn flour, medicinals, seed crops, live plants, and
other products; I should have written out his whole paragraph, I guess. I
did note that a small transect in a healthy P/J forest caught 30 species,
and assumed--improperly--some familiarity with agroforestry and how it could
be applied. Maybe someone else will take the time to detail that. I hadn't
realized my words would be taken to mean that we could eat juniper trees or
bring back mastodons.

> And I think some of your ecological pronouncements suspect as
> well.  "The myth that trees reduce the groundwater..." What are you talking
> about?

It's a myth. Trees increase rainfall by harvesting water from multiple
sources (do I gotta list 'em all?), thus increasing net atmospheric moisture
circulation, net groundwater content, and net streamflow, far more than
shrubs, herbs, or grass. I stated a few of the mechanisms in my post. Read
Mollison, "Permaculture Designer's Manual," p 142-150 for some details. Read
any of dozens of papers on the subject, provided they aren't written by
those with an economic agenda for cutting trees. Or just open your eyes,
look outdoors, and watch how a tree works.

>Where does all that moisture coursing through the trees come from?
> the Atmosphere, direct absorption of rainfall?

Sarcasm ignored, it comes from many sources. For example, leaves harvest
atmospheric humidity (fog, dew, etc, when there is any) and direct it to
roots, providing up to 3 times the precipitation received as rain. Again,
see Mollison and his references. Much rain--40% or so--comes from other
trees (radioisotope studies confirm this); it's not like trees steal water
and throw it away to vanish forever. Yes, it can be difficult to establish
mesic species in low-rainfall areas under individual trees that have high
evopotranspiration rates, but then, doing that may be inappropriate. So wait
awhile to do it: Even in the desert, I've seen tree cover create ideal
conditions for mesic species (check out any good permaculture site in NM or
AZ--there are many--or anywhere, for that matter).

>Given the same moisture
> status, a closed woody cover will have a similar evapotranspiration rate as
> a closed green grassland.

That's simply not true, unless you mean something tricky by
"evapotranspiration rate." With their deeper roots and vastly greater leaf
surface area, trees absorb, harvest, and transpire far more water than
grass. The transpiration is why they get the bad rap. But, to repeat, this
water doesn't go "away," it returns as rain and is held in soil and in the
(vastly greater) tree biomass. This larger volume of water-cycling performed
by trees, plus high humidity levels under the much larger canopy volume
(plus many other factors) translate to higher moisture levels, and more net
moisture, in air and soil. The hypothesis is: more trees, more rain, fewer
deserts. We certainly know the converse is true.

Sure, many forces are at work to create deserts. But cutting trees won't
slow the trend, and may accelerate it (I am reminded of the anti
climate-change arguments). In the case of P/J forests, when they replace
grassland, that's a strong ecological statement, and we'd do well to assess
what is happening before clearing it back. Is simple fire suppression the
cause? Or is it grazing that prevents reestablishment of non-woody species?
Or is nature simply saying "stop sucking money out of this land for a
while?"

In the 1940s and 50s, ranchers and farmers in NM and AZ complained that
riparian trees were stealing water from creeks and rivers. The government
created a big program to cut down trees on thousands of miles of
watercourses. The result: Seasonal creeks disappeared in huge numbers, and
flow of year-round creeks diminished. So they established a re-planting
program, and flows increased.
> 
> Time to learn a little science to allow some testing of opinions passing
> off as facts. 

Now that irritates me enough to haul out my science credentials: 15 years as
a genetics and biochemistry researcher at Harvard, Tufts, and Univ. of
Washington, and 8 years managing the scientific communications group at a
1200-employee biotech firm. Summers doing ecology fieldwork for the Forest
Service, permaculture teaching for 5 years, and a book in press on
ecological gardening (out in February, my publisher says!). I think I can
winnow fact from hearsay. The hard part is learning to question the
reductionist specialists who have only a piece of the puzzle (like those who
teach us that trees steal water, period).

If I were feeling snide, I'd reply that it's time to learn a little
permaculture.

> And to equate a modern grain farm with a cattle ranch is silly.

My equation was that they are both unsustainable forms of land use. I'm
aware that they are not identical practices. List-servs would be a lot more
enjoyable if we--and I include myself here--would honestly attempt to see
what the other person is driving at through the limited medium of writing,
rather than pouncing on a perceived weakness and sneering. It sounds like
beneath the surface disagreements we share many of the same experiences,
concerns, and beliefs.

Toby