Regarding
"This land is NOT viable, but it is the source of the 'alternative/ecological/sustainable/permaculture' crowd. Ok, but as the pressure comes on, a lot of land down there is going to be re cleared from 'invasive' trees and the rest and be put back into production crops. Fine, but that action will utterly recreate the rainfall patterns in Puna."
and
"Crops recreating the rainfall patterns?
In a tradewinds weather system doesn't the prevailing weather determine the growth patterns and not the other way around? I thought that's why it's greener here on the windward side."
...I'd wondered about those points myself. Seems like the magnitude of the windward/leeward island precipitation pattern would far eclipse effects of evapotranspiration from vegetation in most situations, the possible exception being in marginally xeric zones. Decades ago my professor Otto Soemarwoto described the water competition between fuelwood agroforestry versus foodcrop agriculture with the conclusion (if I remember correctly) that trees generally use up more water than do most food crops. This note on evapotranspiration rates of eucalyptus trees versus groupdcrops looks consistent, just glancing at the data (
http://www.ramin.com.au/creekcare/transp...port.shtml).
The thick haze which forms over many Mainland forests on hot afternoons is a visible indication of all the water the trees are transpiring. An island, though, even an island as large as the Big Island, is perhaps too small for forests to essentially create their own small weather system of sorts since they are not present in vast tracts as in the interior region of Alaska or around the Great Lakes. So, if that all holds up as accurate, then it seems like a mixed tree-and-groundcrops system (polyculture, with different levels) in relatively wet places like Puna, Hilo, and points northward along the Hamakua Coast would actually come out ahead over pure agroforests in terms of water retention (though it seems like soil conditions and not water shortage would generally be the limitation there). I'd think the places where exactly what is planted and in which configuration might matter most as regards transpiration versus growth is in the zones where conditions are semi-arid, as suggested by this paper "Why tree-crop interactions in agroforestry appear at odds with tree-grass interactions in tropical savannahs" by Ong (
http://www.ingentaconnect.com/content/kl...1/00236109)
As for the other point, "This land is NOT viable, but it is the source of the 'alternative/ecological/sustainable/permaculture' crowd" I'd agree one is doomed from the outset if the only model of farming one has in mind is that of plowing soil with a tractor, mule, or babushka. In many places in Puna that would be plowing rocks more than plowing soil, per se. This does not mean, though, that overall productivity of even very rocky land cannot be quite high when that rocky land is blessed with abundant rainfall and sunlight. I've seen the "alternative/ecological/sustainable/permaculture' crowd" do some amazing things with raised beds and integrated polycultures tying together plant and animal productivity (such as rabbits, chickens, and fish with raised beds, trees, and ponds). This is nothing new, either, though the Rodale folks and some others like them appear to have made some nifty improvements on some aspects of traditional homegarden systems.
In Indonesia the combination of rice cultivation in fields with diverse productivity of everything else in
pekarangan (homegardens which mimic the trophic energy and nutrient capture levels of natural forest but with cultivars directly useful to humans) sustained dense populations and high civilizations for thousands of years (that useful term "
pekarangan," by the way, is pronounced "Peck-ahr-Rrrrang-an" -trill the r). Here are some good refs on that traditional homegarden approach:
http://nzdl.sadl.uleth.ca/cgi-bin/library?e=d-00000-00---off-0fnl2.2--00-0--0-10-0---0---0prompt-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0-0-11-1-0utfZz-8-00&a=d&c=fnl2.2&cl=CL3.66&d=HASH0149e1432e7023d7127fa8ec.1.7
"The Javanese home garden as an integrated agro-ecosystem" by Otto Soemarwoto, Idjah Soemarwato, Karyono, E. M. Soekartadiredja, and A. Ramlan, Institute of Ecology, Padjadjaran University, Bandung, Indonesia.
http://books.google.com/books?id=4ZWtqbHQ0pwC&pg=PA161&lpg=PA161&dq=pekarangan+homegarden&source=web&ots=jlHNkbS7jw&sig=w1YV0uOVM0PJYtJz5MZQYyjSO1w&hl=en&sa=X&oi=book_result&resnum=3&ct=result
Theoretical Ecology: Principles and Applications, by Robert McCredie May & Angela R. McLean.
http://209.85.141.104/search?q=cache:cjcdEmJihtUJ:www.gerrymarten.com/traditional-agriculture/pdfs/Traditional-Agriculture-chapter-06.pdf+pekarangan+homegarden&hl=en&ct=clnk&cd=1&gl=us&client=firefox-a
Traditional Agroforestry in West Java: The Pekarangan (Homegarden) and
Kebun/Talun (Annual/Perennial Rotation) Cropping Systems, by Linda Christanty, Oekan S. Abdoellah, Gerald G. Marten, and ]ohan Iskandar.
So, I'd by no means discount the potential agricultural productivity of even very rocky places in Puna as long as there is abundant water, sunlight, access to information on viable traditional systems, and the will to adapt those approaches to local conditions.