PERMACULTURE
EVALUATION
CENTRE
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94 Need to understand patterns of availability and usage requirements of renewable resources
Consider replacement time and how long products made from a resource will be in use
95 Total size of a given resource is also relevant
96 Agriculture has changed from prime means of harvesting renewable resources to one of the largest consumers of non-renewables
EMERGY suggests photovoltaic cells show negative net energy results
97 Trees are better converters of very dilute solar energy into wood which is substitute for fossil fuels, and forests have other benefits …
98 Solar cells only justified in remote situations or sunny dry climates, but do at least make us aware of need to use electricity sparingly
99 ‘Clean green’ technology is an illusion – we will have to rely on natural systems – self maintaining wild resources. How and when we harvest will be as important as how much.
Need to guard against over exploiting wild systems because they are perceived as ‘free’
100 Sustainable harvesting of native forests: remove little trees to grow big trees
101 Most indigenous wildlife species (along with native forests) have achieved the dubious distinction of being both worthless and ‘sacred’. When wild resources have low value the cheapest and most wasteful harvesting methods are used ….
102 Build soil fertility via biological methods – pioneer plants like legumes are useful
104 Africa – corn is soil depleting – woody perennial legumes increase fertility without the need for synthetics
105 Bullocks could work while being fed rough pasture
Horses are capable of faster work but need more concentrated feed (oats) from good cropland
Horses would be useful in small scale forestry work but the skills have disappeared
106 ‘Free’ water purification by flowing rivers ruined by industrial and farm pollution
107 Increasingly natural systems are recognised as the best models for water purification. Reed beds, streamside vegetation, willows, water filtering through soil – all useful
108 Some environmental technology is too wasteful of embodied energy. Nature often uses apparent wastes to expand and strengthen living systems, which in turn provide people with more resources