Wikipedia has really nice maps on cultivation of various grains, for ex. world wide wheat yield, showing the regions that cultivate the grain on a large enough scale. An interesting exercise is to make a composite image of such maps for various grains to highlight the bread baskets of the world and see which regions end up as bread deserts. While the result of such a map would go into annals of obvious science, with deserts, rain forests and tundra regions showing no significant cereal production, I wanted to perform the exercise to see if any not so trivial insight can be obtained.

Of the major cereal grains such maps are readily available for Rice, Maize, Millet, Wheat and Oats on Wikipedia. I could not find such maps for Sorghum, Barley and Quinoa. I created the composite image using Matlab with no regards to color scaling on each graph, since I was adding apples and oranges. The resulting composite map is shown below.

As expected the regions showing little or no grain cultivation are deserts, rain forests and the colder parts of northern hemisphere. It should be noted that the intensity of color has no meaning in this graph. While the composite map yielded no insight, I found another map (also reproduced above) showing the population density of the world.

It can be seen comparing the two, that there is an obvious correlation between regions growing cereal grains and regions with high population density. However the interesting observation is that the correlation only exists in the old world and not in the new world. Is this due to the fact that much of new world was colonized after reduction in labor required for agriculture, or the transportation networks for distributing produce developed quickly in the new world compared to the old world? I think it is the latter.

Analysis Caveats: 1) Missing grains like sorghum and barley will make large differences in composite plots, especially for Africa

2) An ideal comparison would require calculating the graph of the calorific value per hectare to correlate with population density