[Scpg] steep permaculture slope ideas?
Owen Dell
owen at owendell.com
Wed Sep 8 06:36:53 PDT 2010
Yes, it's vital to be on site in order to understand what is specific to that particular situation. What is the soil type? What is the nature of the underlying geology? What plants, native and introduced, are currently on site? What is the native and introduced fauna? What is the aspect of the slope (N/S/E/W)? How much if any water runs onto the site from elsewhere? How much water soaks into the soil and how much runs off? Where does the runoff water go? What is the history of the site in terms of land use, erosion problems, soil movement, fires, etc.? There are many questions to be asked, and most people don't even know that these questions exist. That is why I caution that in addition to seeking site-appropriate strategies, a knowledgeable professional be consulted when working on slopes where poor decisions can lead, literally, to disaster.
True success comes partly from knowing what is local and particular to the site. Each site is unique. There are no general, non-local conditions; there are only principles that can be applied to local conditions. And true success is measured in centuries, not months or years, of stability and health of the system without the need for external inputs.
Type conversion of any given piece of land from one ecosystem to another is not to be done without taking into account many factors. Some land is not suitable for production, or for various reasons it is not safe or wise to disrupt the native conditions. I assert that no form of human intervention, even permaculture, is better for any given piece of land than the original native ecosystem. Permaculture is a fit practice for healing disturbed and urban lands and making them productive, but when it encroaches upon wildlands it becomes just another pernicious human activity. Agriculture in general is a massive wipeout of ecosystems that have evolved for millions of years. Agriculture supplants complex ecosystems with overly simple, totalitarian ones that depend on the continuing brutal exclusion of all forms of life that are not of "economic value." To be in harmony with our surroundings, we should be hunting and gathering, removing individual food units from intact wild ecosystems. Unfortunately, there are far too many of us for that to work anymore, but it remains the one truly environmentally justifiable way of surviving. It is what all the other animals do. As a result of our overpopulation, we are forced to turn to various forms of agriculture to meet our needs. Permaculture is helpful as long as it remains within its proper bounds, but it is important to understand that all forms of agriculture, including permaculture, are destructive.
I mention all of this because the original posting was about growing food on a slope. I know nothing about that slope, but if it is in or close to a native condition I would, were I on site as a consultant, probably advise against destroying the native flora and fauna in order to grow food. Chaparral or coastal sage scrub lands in our area are not particularly or not at all suited to any form of agriculture, and the stability of such lands is often dependent upon the extensive root systems of native plants. Therefore it is my opinion, consistent with commonly accepted good practice, that such areas are best left alone. Not to mention the fact that wild places, however homely they may seem to the casual observer, perform essential ecological services that cannot necessarily (or in most or all cases cannot ever) be replicated or improved upon by human manipulation. And of course, there is the matter of the morality of destroying wild places, on which I am adamant that such destruction, in the name of any human cause, including permaculture, is wrong. We must not use permaculture as a rationale for ruining natural systems.
On the other hand, if this is a disturbed slope which has not been in a native condition for some time, and if I were assured by a geotechnical expert that there was no risk of either surface erosion or landslides (called, dramatically, "mass wasting" in the profession), I would certainly consider some form of productive use. Most likely my approach would concentrate on low water use trees and shrubs and perennial plants, since it's very challenging to grow annual crops on sloping terrain. But I would also urge that restoration of the native ecosystem be considered. (Of course, in our area there is also the matter of fire, and when people move into wildland interface areas they create the conditions for destruction of wildness in the name of fire safety. That is a whole other big question that I won't get into here.)
Looking to one of the specific strategies under discussion here, grasses are indeed a diverse group of plants. Because many grasses, particularly annual species, are shallow rooting, they form a slip zone at the interface immediately below the bottom of the root mat they develop. In the absence of deeper-rooting shrubs and trees, there are no roots below 12 inches to help consolidate and hold the soil in place. The number of stem penetrations per square foot in a grassland runs in the thousands (compared to one or fewer stem penetrations per square foot for shrubs and trees), and the individual grass blades act as tiny funnels to channel rainwater into the soil. This results in supersaturation, and the slip zone becomes lubricated. Due to the supersaturation, the soil becomes both heavy and plastic. Eventually, gravity overcomes the diminished friction at the slip zone, and the entire mat of soggy soil and grasses slides downhill. In an unstable soil, the lack of roots in deeper horizons can result in a far worse outcome than mere loss of the foot or so of surface soil; the entire mass of soil down to a depth of many feet can collapse onto the area below.
I should also point out that mass wasting can occur after many years of seemingly successful type conversion. It takes years for the root systems of native plants to decay to the point where they have stopped performing soil-holding services. It is common that some time after a piece of land has been turned to agriculture or urban landscaping, it will "suddenly" fail. This happens all the time, and people are mystified as to the cause. It is simple: the fine and delicate equipoise of the native conditions was interrupted, with a catastrophic outcome. We mess with land at our peril, and at the peril of others.
I hope the above information is helpful to all. There is, of course, much more to this. I am happy to continue the discussion and to hear dissenting opinions.
Owen
Owen E. Dell, ASLA
Owen Dell & Associates
Landscape Architect • Educator • Author
P.O. Box 30433 • Santa Barbara, CA 93130
805 962-3253
owen at owendell.com
www.owendell.com
QUOTE OF THE DAY
"O take heart, my brothers. Even now...with every leader & every resource &
every strategy of every nation on Earth arrayed against Her -- even now O even
now! my brothers, Life is in no danger of losing the argument! For after all...
(as will be shown) She has only to change the subject."
Kenneth Patchen
from Hallelujah Anyway, 1960
On Sep 7, 2010, at 2:14 PM, Dan Hemenway wrote:
> Owen:
> If it isn't practical, it isn't permaculture. That's basic. That's not to say that the word isn't misused, but that is not the fault of the word, or the practice that the word represents.
> Grasses are a huge family and quite variable. I was silently skeptical, myself, about a plants that are largely mat-rooted holding soil in place on a steep bank. "Bunch" grass could be any of hundreds of species. On the other hand, with the correct woody plants, grasses may be OK. We are talking too much in generalities here, and the specifics of site and of habit of candidate species for the site are important. Neither you, nor I, nor anyone who has not visited the site can know what will work. On the other hand, I am profoundly skeptical of an approach that favors surface runoff, since that is just another way of saying soil erosion, particularly on steep slopes.
>
> Dan Hemenway
>
>
>
> -----Original Message-----
> From: Owen Dell <owen at owendell.com>
> To: John Calvert <jcalvert at crystal3.com>
> Cc: scpg at arashi.com
> Sent: Mon, Sep 6, 2010 1:29 pm
> Subject: Re: [Scpg] steep permaculture slope ideas?
>
> Grass is a very poor way to protect slopes against erosion. The large number of stem penetrations results in a very effective transmission of water into the soil, which can lead to supersaturation and slope failure. No offense to anyone, but I recommend that people not speculate about what is going to work. There are accepted standards for this kind of activity. Permaculture is a great thing, but it doesn't always address real-world issues and it isn't always right. Slope failures can cost hundreds of thousands of dollars to fix, and the cost is not covered by insurance. I say again, PLEASE consult a professional before you go off implementing half-cocked ideas.
>
> Owen
>
> Owen E. Dell, ASLA
> Owen Dell & Associates
> Landscape Architect • Educator • Author
> P.O. Box 30433 • Santa Barbara, CA 93130
> 805 962-3253
> owen at owendell.com
> www.owendell.com
>
> QUOTE OF THE DAY
>
> "You take a number of small steps which you believe are right,
> thinking maybe tomorrow somebody will treat this as a dangerous
> provocation. And then you wait. If there is no reaction, you take
> another step: courage is only an accumulation of small steps."
> George Konrad
> Hungarian novelist & essayist
>
>
>
> On Sep 6, 2010, at 10:23 AM, John Calvert wrote:
>
> >
> > I was gonna say grass... the bunch grass sounds like a very good idea.
> >
> > lfunkhouser at juno.com wrote:
> >> Kevin,
> >>
> >> You might also want to talk to Mary Scaran, who is an acupuncturist >> in SB (she's in the phone book) and has a very steep slope running >> the entire length of her oak wooded and desert upland property that >> is permeated by a spring. She has planted lots of things to >> stabilize, including Persian mulberry trees (edible!) and some kind >> of grass -- can't remember which -- but a type of bunch grass that >> she selected for its very specific properties of soil >> stabilization. Mary practices permaculture, studies horticulture, >> and is a very fine acupuncturist.
> >>
> >> Good luck.
> >>
> >> --Laura
> >>
> >> ---------- Original Message ----------
> >> From: Kevin Gleason <kevin at kevingleasonart.com>
> >> To: John Calvert <jcalvert at crystal3.com>
> >> Cc: scpg at arashi.com
> >> Subject: Re: [Scpg] steep permaculture slope ideas?
> >> Date: Mon, 6 Sep 2010 07:14:15 -0700
> >>
> >> Thanks, John, and all others who have replied. This is such a >> helpful community. I am going to look into the "net and pan" >> technique Susan recommended and am trying to find some good >> "pinning" shrubs and trees per Dan's advice. I need to pay good >> attention to the plants that seem to be holding up west facing >> slopes next time I'm out hiking. It is okay with me if this >> really steep section doesn't grow food.... Maybe I'll just grow >> food for the birds there.
> >> I appreciate eveyone's help.
> >> Thanks!
> >>
> >>
> >> On Sep 5, 2010, at 9:22 PM, John Calvert wrote:
> >>
> >> >
> >> >
> >> > I started out writing a response to this, looking in the >> direction > of what grows native on our steep coastal mountain >> canyons.
> >> >
> >> > But I realize that there isn't much edible on the really steep > >> slopes. It seems the more fruit-bearing types are more likely to >> > appear where there's better soil and moisture.
> >> >
> >> > So, that leaves the plants that do well in poor soil and least > >> moisture...
> >> >
> >> > nopal cactus, various wild sages, maybe fit in a hollyleaf >> cherry, > chia ?, maybe some kind of mulberry, wild golden currant >> (?).
> >> >
> >> > so, mostly natives, and then some select fruit-bearing plantings >> w/ > drip irrigation. ?
> >> >
> >> > JC
> >> >
> >> >
> >> > Kevin Gleason wrote:
> >> >> Hi all,
> >> >>
> >> >> I was wondering if anyone has good advice for creating a garden >> on >> a VERY steep slope (more than 45 degrees.) I'd love some >> feedback >> on alternative terracing methods, whether this is too >> steep for >> small swales, good soil-holding, drought-tolerant >> ground covers >> and other plants that would be useful and other >> ideas. I remember >> hearing Brock Dolman talking about making >> retaining walls with >> burlap tubes filled with soil and a little >> cement. Anybody tried it?
> >> >>
> >> >> Thanks for your help!
> >> >> Kevin
> >> >> _______________________________________________
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> >> >>
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