It is a very important question, and one which is difficult to answer. The availability of resources is a complicated topic, with increased demand and price and better technology making sources available which would remain untapped. For example the Swiss were able to greatly increase their food production during WWII with the "Anbauschlacht", by using far more of the relative poor or difficult areas, supporting agriculture with capital and working power and by switching from milk to basic products like grain. During WWII the the German (or Japanese) lack of natural fuel could not be overcome by a belated effort to produce the in-efficient synthetic fuel. The worldwide dominant market economy does not pose such barriers to single countries but the basic forces of available and potential supply, demand, pricing, costs and technology are still there.