erryl:

I don't, however, believe that the centuries long trend toward more efficient agriculture and food being a smaller portion of our expenses (a pretty good sign of prosperity) has necessarily been reversed or that the recent change to rapid inflation in food prices has to be inevitable.  It may happen, but it doesn't have to be that way...  To me, it is much like arguing that the world's standard of living must decline... I disagree.

erryl

It's not clear to me that we're necessarily moving toward more efficient agriculture.  The problem is we're looking at a confluence of two trends.  On the one hand perhaps we'll see more agricultural efficiency in the developing world, but that is offset by the consumption of more meat.  As livestock is much more energy intensive to produce, that can more than offset any efficiency improvements in the raising of the grains and other food to feed them. 

For what it's worth, I do believe there is a strong chance that U.S. standard of living may need to decline.  I don't think there has to be a collapse, but what that might mean is eating a small piece of meat, with more grains and vegetables, rather than a massive slab of meat with only a tiny bit of vegetables on the side.  It would actually be good for us too, considering the increasing obesity in our country, which leads to poorer overall health. 

Increased efficiency can only get you so far.  It's been estimated that for the whole world to live at a U.S. standard of living we'd need the resources of 2.5 Earths.  That is a massive necessary increase in efficiency, and for some resources it may be an impossible goal (in other words you can't simply do more with less, you actually have to change and do something differently). 

As other countries continue to take more of their fair share, I don't see how we can avoid feeling that in the U.S.  If how one measure's standard of living by overall quality of life, then I think we can always keep improving it.  But if one measure's only by wanton overconsumption then we'll have trouble maintaining our current level.