You forget the human factor.

People is depended on what the large farmer land produce.  They will do their best to avoid the soil erosion and other damages, otherwise they will be hungry and die.  You would say certain place is undefensable against nature, then you need careful analysis and/or spread out the location.  That is your value as a investor. 

About Gold, it was used as a currency for a long time, it is rare and hard to mine.  It also have industry values.  Looking through the history, its function is to measure (a little used currency).  Look at the charts, you decide yourself, which one is a better measurement, US$ or Gold?  Which country can run on the Gold?  You spread all the gold in the world to everyone on earth, do we have a few of grams each?  Currency's basic function is to be used on exchange.  That will not do it.  Also if there are a big disaster, which one will be more useful, farm land or gold? 

human is keeping making progress, life is getting better too.  As a human, you want to be productive and smart.  Which currency can promote that?  Paper currency or gold?  A little inflation drive you go faster, under control inflaction (2%) will still work as a stable measurement.  That is a art to manage the currency against inflation, deflation, to avoid the economic disaster.  Ben at least avoid another Depression no matter whatever they are disagreed with him.