The world is fed mainly by a dozen plant species, and most agricultural countries have specialists for their country’s major crops. The world also has thousands of minor economic species, which potentially are as important ecologically and economically as the big dozen, but there are not enough specialists to study them. There is an overwhelming number of climatological, pedological, anthropological, latitudinal, and biological variables associated with these minor species.
When asked to make crop recommendations for remote areas, I often find it convenient to refer to the Holdridge Life Zone System as originally published in 1947. In Table 1, I give an oversimplified schematic presentation of some Holdridge Life Zone parameters, based on his 1947 version.