[permaculture] Toby Hemenway: Thoughts on pc design, ecology and balance of nature
lfljvenaura at gmail.com
Thu Mar 28 16:38:02 EDT 2019
Toby Hemenway: Thoughts on pc design, ecology and balance of nature
From: hemenway at jeffnet.org (Toby Hemenway)
Date: 24 Dec 1999 17:44:33 GMT
Personal data: I live in rural Oregon, USA, write,
consult and teach Pc for a living, and just edited the most recent issue
of the Permaculture Activist. But enough about me.)
>> Myk (I think that was Mky Rushton, a UK permaculturist - LL) wrote,
>> Classical ecology speaks of the 'balance of nature' and 'ecosystems
>> equilibrium' - ecology now show us that there is no such thing as
balance or equilibrium
I¹m glad to see this being raised. Much of Pc, of course, is spot-on,
since it derives primarily from observation. But: since Pc was developed
in the 1970s, many of its concepts are based on the now-outmoded view of
ecology that Myk describes, and I¹ve been concerned about this. One of the
most popular definitions of Pc says we¹re trying to design systems with
³the stability and resilience of nature.² And we take for granted that
³diversity creates stability.² Yet both of these ideas have been largely
discredited in the post-70s revolution in ecology. Even the idea of
succession has been challenged as a myth.
In his excellent book ³The Balance of Nature?² Stuart Pimm points out that
ecosystems are far from stable; that patchiness, disturbance, and invasion
are the rule. He says that the concept of stability is very deceptive,
that people use it in at least 5 ways, including the time a system takes
to recover from disturbance (resilience), how long it resists a perturbing
force before changing (persistence), how much the change in one element
affects the whole system (resistance), how long all elements take to
return to their original state after disturbance (stability) and how
resistant the system is to invading species (invasibility). So what are we
creating when we try to make ³stable² guilds and gardens?
I think there¹s a lot of meat in the ³resistance to invasion² idea. A good
tight guild should repel pests, invasive grasses, etc..
And diversity does not necessarily create stability. Examples abound of
very stable, very simple ecosystems, and on the other hand, adding new
elements to a ³stable² ecosystem can make it collapse or alter it
drastically. I¹m from the ³throw a zillion species together and let them
duke it out² school of Pc design, but sometimes this fails miserably.
Obviously we need to take nature as our guide when we design, but often
whem we assume nature is doing one thing, she turns out to be doing
something very different. It concerns me that some of Mollison¹s ideas
stem from a now-outmoded view of ecology, and we¹re using them as the
basis for a design system.
Lawrence F. London, Jr.
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