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Food pyramid question

 
Joe Wexler
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I'm new to permaculture and just started Bill Mollison's manual. In chapter 2.7, he says" if the frog eats 10 kg of grasshoppers to make one kilo of frog, it doesn't keep the 10 kg in a bag, but excretes 9kg or more back to earth as manure"
He also says "so now, the carp (at 80 years old and 10kg weight) has eaten 100x10kg = 1000kg of frogs and insects, and has returned 990kg of digested material per year back to the pond, to grow more herbage"

But don't these statements ignore resparation, which results in a large amount of carbon entering the atmosphere as C02? Plus lots of energy was expended. In other words, after an animal stops growing isn't it a drag on the system? Yes it may increase plant fertility but he doesn't mention that, simply claiming that the fully grown animals are simply recyclers of nutrients. But aren't they doing the exact opposite of our goal as farmers, which is to harvest energy from the sun and carbon from the atmosphere?

 
Bob Knows
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Joe Wexler wrote:
In other words, after an animal stops growing isn't it a drag on the system? Yes it may increase plant fertility but he doesn't mention that, simply claiming that the fully grown animals are simply recyclers of nutrients.



You have hit on a basic rule of raising animals for meat, Joe. For the first few years of an animal's life it converts food into meat. After that it consumes food and produces waste for several more but does not produce more meat. That truth was known by pre historic goat herders who's trash heaps contained far more bones from yearling goats than from old goats. Its still true today. My local beef rancher raises beef for a year or so and then they go to great pasture in the sky (and to my freezer.)

In the wild the knowledge and skills of fully grown animals are life skills taught to younger generations, they also breed and protect the younger ones. Mature animals are part of the system, not a drag on the system.
 
Paul Cereghino
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I think this kind of questioning is really valuable. The numbers I have seen is roughly half the sun energy is respired, half is passed as waste, and a fraction retained as tissue--so for each step in a food web you are losing around half to entropy.

The problem is that we can't really stop this process! All captured energy is lost. All systems wind down, particularly in tropical climates where decomposition rates are high with constant temperature and heat. So you DO need to tend to your primary production side.. maximize capture through plant biomass production. That is where perennial plants and forest are so compelling, is in their ability to capture and store energy.

The value of an animal, is that you are leveraging the wind down, by capturing both the animals work, the concentration of nutrients in manure that you can use to drive other processes, and ultimately the animals body, which is derived of material that may otherwise not suit human consumption. Because you MUST have a decomposition cycle that winds down energy content, it is really just a matter of designing that cycle to trap and cycle nutrients and maximize the utility of the work.
 
R Scott
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Animals actually HELP sequester carbon, I don't consider that a drag.

 
Paul Cereghino
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There are so many animal-carbon interactions!

The dead bodies of some soil biota may form relatively stable fraction of humus... on the other hand there have been both field and lab experiments that show earthworms accelerate decomposition of surface litter.

There is some compelling evidence that in semi-arid or arid landscapes, intense short duration grazing of cows can accelerate soil development and increase cover (the Savory hypothesis)--I would call this an effect of managing grazing pattern, as other grazing patterns have accelerated desertification.

Beaver create large areas of anoxic soils that result in peat development and increased productivity at a landscape scale.

Moose can arrest forest development, and then wolves can support reforestation by eating moose...

round and around it goes...

 
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