As mentioned in my previous posts, the one billion undernourished persons in the world generally have some food. What they lack is primarily dietary fat, and secondarily protein. Some of the hungry may also need some additional carbs. The additional macronutrients that they need to move from undernourished to properly nourished can be estimated (very approximately) as follows:
1.98E+14 kcal from fat
7.70E+13 kcal from protein
7.00E+13 kcal from carbs
This can also be expressed as units of weight (metric tonnes)
22,400,000 tonnes from fat
19,900,000 tonnes from protein
18,100,000 tonnes from carbs
How much land would it take to grow that amount of protein, fat, and carbohydrates? Let’s simplify the math by supposing that each hectare of land (2.471 acres) would be used to grow one crop, and that crop would provide only one macronutrient. So we will need three different types of crops, one for protein, one for fat, and one for carbs.
Food plants vary in the amount of each macronutrient that they provide per crop. However, quite a few different food plants can provide at least 525 kg of protein per hectare per crop (ha-crop), or at least 525 kg of oil/ha-crop, or at least 2130 kg of carbs/ha-crop. Applying this level of productivity to the above stated need gives us these values:
42.7 million hectares for fat
37.9 million hectares for protein
8.5 million hectare for carbohydrates
Total: 89.1 million hectares (200 million acres)
We could reduce the amount of land needed by choosing the most productive crop for each macronutrient. But, in practical terms, it is better to have a variety of different crops that provide the necessary additional macronutrients. Also, if the crops are grown in the developing world, the yields will often be lower than with commercial agriculture in the developed nations. So we don’t want to underestimate the amount of land needed.
But let’s look at some specific crops, and see how they might reduce the above numbers.
At the low end of yields, chufa provides 1920 kg of fat per crop. So we would only need 11.7 million hectares of chufa to obtain the requisite amount of dietary fat.
For protein, we could grow soybeans, at 1079 kg of protein per crop. Then we would need only 18.5 million hectares to meet our target value for protein production.
For carbs, the macronutrient yield is going to vary based more on the growing conditions than on the choice of crop. We could grow rice, for example. At a low yield the carb productivity is 2554 kg carbs/ha-crop, but at a high yield the value is 4684 kg of carbs/ha-crop. (The low yield is the FAOSTAT 2009 world average; the high yield is the USA average.) This would place the land needed to grow carbs at between 7.1 and 3.9 million hectares.
The total is then 37.3 to 34.1 million hectares (depending on the productivity value for the rice), which is about 90 million acres.
So to produce the additional macronutrients needed by the estimated one billion hungry of the world would take between 35 and 90 million hectares, as a rough estimate.
According to the FAOSTAT Resources database, the world had 4,889,048,000 hectares of agricultural land in 2009 (most recent year with world data). So the 90 million hectares is only 1.85% (0.0185) of the total agricultural land in the world. A two-percent expansion of agricultural land would be enough to end world hunger, if the appropriate crops were grown on that land, and the food were distributed to those in need.
And that assumes only one crop per hectare per year. For two crops per ha-year, you can halve all those numbers: 17.5 to 45 million hectares, and less than one percent expansion of the total agricultural land in the world. World hunger is a vast problem, but the various possible solutions, according to my analysis, all require only very modest changes to the world agricultural system.