I am definitely not a soil person but I am aware of this impoverishment. Your stat on corn yields in Africa means that farmers there are averaging one - eighteenth of the production that could be had under prime soil conditions. This is one of those issues - like mosquito nets to protect against malaria - that is not flashy but that merits sustained attention and action.

Well, as I've posted elsewhere, in nature animals generally excrete their waste and eventually die and decompose, in the places where they forage, so you have a closed loop, especially with respect to vital minerals.  Agriculture and sanitation, to the extent that they're practiced with "modern" methods, break that loop.  The only permanent solution is to close it again, which is going to require a major rethinking of how, why, and in many cases whether, we apply technology to the practice of agriculture.

Which brings me to the point: I have to wonder when as a culture and more widely as a species, are we going to learn to start properly identifying which is the horse end, and which the cart?  When will we learn to make the vital distinction, between the proximate causes of problems, and the ultimate causes of them?

The proximate cause of hunger in many areas of sub-Saharan Africa is poor soil conditions, but the ultimate cause of both the hunger and the poor soil conditions is too many people.  500 pounds of corn per acre is only a problem if you are trying to support a population per-acre, that needs more than that.  

A century and a half ago, farmers growing corn in incredibly rich and fertile soils of the american midwest were netting 1250 pounds of corn per acre.  Today the same yield would leave many milions starving.

I'm afraid that the net effect of finding clever technological solutions to these problems, is nothing more than to make us irretrievably dependent on that technology.  This cuts off our avenues of retreat, and we succumb to the illusion that more technology will somehow get us out of the jam.

That illusion will hold until we start running out of the non-renewable material resources that these solutions depend on.  When that happens, we will be helpless to prevent a downward adjustment.

The question for humanity is going to be, when the time for that downward adjustment arrives, is it going to be a small and bearable step down or a catastrophic plunge off a high cliff?

I think our real problem, the problem that we do not seem to be recognizing or addressing at all, is learning how to make do with less.  Because what we're "making do" with now, is almost certainly already more than we can permanently sustain.

zaiquiri, I don't disagree with much--really anything--that you've said, EXCEPT that I don't think "making do with less" is really a realistic option for the human race as a whole.

Nevertheless, it's good to keep talking about these issues.  Humanity is out on a limb ecologically speaking, WAY out, and the only thing keeping us from crashing down in the most painful way is technology.  The trouble is, as this post highlights, our current technology is nonsustainable.  But as rational and humble and, to me, personally appealing as your neo-Luddite, do-with-less prescription might be, I just don't see the human race getting it together to make the required sacrifices.  We haven't evolved for renunciation.  For every Icelandic vegetarian prepared to forgo child bearing and car ownership and to live in a one bedroom high rise flat heated with geothermal steam, there are thirty-five Indians saying "Please to have my Land Rover now, and my air con, and my steak dinner, and my giant screen LCD tv so I may watch this new Indian Premiere League cricket."  And honestly, who can blame them?

So I see only two possible futures:

Either

We make some new large scale technological breakthroughs that solve our fundamental problems of material existence--sustainable food production, carbon-free energy production--in such a way that most of the world's population can be brought up to a high enough standard of living that birthrates decline and the human population stabilizes or even declines a bit.

Or

We make no such changes, food production collapses, there is famine and secondary war, the human population shrinks precipitously (i.e. people die in large numbers), civilization collapses and the best we can hope for is that no one gets so crazy from hunger that he initiates a nuclear exchange.

Barring a full bore nuclear war, future number 2 would actually be better for the non-human world, but being the happy Homo sapiens that I am, I'm angling for future number one.  

"For every Icelandic vegetarian prepared to forgo child bearing and car ownership and to live in a one bedroom high rise flat heated with geothermal steam, there are thirty-five Indians saying "Please to have my Land Rover now, and my air con, and my steak dinner, and my giant screen LCD tv so I may watch this new Indian Premiere League cricket."  And honestly, who can blame them?"

Gimme a break. India is the most vegetarian-friendly civilization there is. And Indians are not crying out for steaks. The new demand in India is mostly poor people moving up to the working class. Its more like "Let me finally buy a TV, let me get a car to SHARE among my extended family, let me eat until I am no longer hungry."

It is amazing how worked up Americans are getting over Indians consuming marginally more than before. Why don't Americans stop buying a car for every member of the family (including the teenagers), stick to one TV set per household and stop overeating. Perhaps the average American can reduce their consumption to about three times the amount the average Indian consumes and then you can worry about how much Indians consume.

"So I see only two possible futures:..."

Even modest cuts in meat consumption in the Western world would actually go a long way to solving out agricultural and water problems. The world doesn't need to go vegetarian but limiting meat consumption to 3-4 meals a week would be much healthier for the individual and would free up more farmland.

I've seen reports that show several pounds of corn, soy and other plants are need to make one pound of beef. It rakes 2500 gallons water to produce 1 pound of beef!

www.vegsource.com/.../pimentel_water.htm