permaculture

[Toby Hemenway <hemenway@jeffnet.org>]

Marsha wrote:

> Toby says "what you add to the sysem has to come from somewhere"  But if we
> work with live systems which include a heavy tree element, that "somewhere"
> is the mother rock, where the tree goes to get its minerals to re-cycle to
> the rest of the system...

In this thread, people have been referring to two different kinds of
systems: human-made, like cities and farms (where we add and take out things
at fairly large energetic and material cost to other systems of similar
size) and natural ecosystems, where losses and mineral inputs are small and
are replaced from  "outside" systems (earth's crust, the air, the sun) that
are so huge as to be effectively infinite. So some of the differences in
definitions that we've been coming up with are due to this.

BTW, In most human-designed systems, the mass comes from minerals or is
pirated from sun-driven ecosystems. In contrast, most of an ecosystem's
biomass comes from water and airborne CO2; a miniscule amount comes from
minerals (e.g. in a hectare of hardwood forest weighing many millions of kg,
there's about 250kg calcium, of which 8kg is lost per year, replaced from
rocks and rain). This gives us a hint as to why so many human systems are
unsustainable. 

In a conventional agroecosystem the lost minerals are imported to the system
as fertilizer. A sustainable agroecosystem would include enough accumulator
plants to replace minerals from subsoil and rocks, in the way Marsha
suggests. If minerals can be fed to plants efficiently, as insoluble
complexes (humus, chelates) instead of poured on as water-soluble fertilizer
(with 50-90% loss), losses from harvest can easily be replaced by rock
weathering, mulches and manures from in-system plants. You can't monocrop
with this system, of course. But I've never thought that you can have
sustainable agriculture if you need far-transported and mined fertilizer.

Toby