A few related points
As nearly half of the world's cereal production is used to produce animal feed, the dietary proportion of meat has a major influence on global food demand (Keyzer et al., 2005). With meat consumption projected to increase from 37.4 kg/person/year in 2000 to over 52 kg/person/year by 2050 (FAO, 2006), cereal requirements for more intensive meat production may increase substantially to more than 50% of total cereal production (Keyzer et al., 2005).
Meat production, however, also has many detrimental effects on the environment, apart from being energy inefficient when animals are fed with food-crops. The area required for production of animal feed is approximately one-third of all arable land. Dietary shifts towards more meat will require a much larger share of cropland for grazing and feed production for the meat industry (FAO, 2006; 2008).
Expansion of land for livestock grazing is a key factor in deforestation, especially in Latin America: some 70% of previously forested land in the Amazon is used as pasture, with feed crops covering a large part of the remainder (FAO, 2006b). About 70% of all grazing land in dry areas is considered degraded, mostly because of overgrazing, compaction and erosion attributable to livestock (FAO, 2006b). Further, the livestock sector has an often unrecognized role in global warming – it is estimated to be responsible for 18% of greenhouse gas emissions, a bigger share than that of transport (FAO, 2006b).
It takes, on average, 3 kg of grain to produce 1 kg of meat, given that part of the production is based on other sources of feed, rangeland and organic waste (FAO, 2006). Currently, 33% of the cropland area is thus used for livestock (FAO, 2006 livestocks long shadow).
Hence, an increased demand for meat results in an accelerated demand for water, crop and rangeland area. Meat production is energy inefficient and environmentally harmful at industrial scales and with intense use of feed crops such as maize and soybeans.
Stabilizing the current meat production per capita by reducing meat consumption in the industrialized world and restraining it worldwide to 2000 level of 37,4 kg/capita in 2050 would free estimated 400 million tons of cereal per year for human consumption – or enough to cover the annual calorie need for 1.2 billion people in 2050.
How many people can be fed with the cereals allocated to animal feed?
Methodology: By 2050, 1,573 million tonnes of cereals will be used annually for non-food (FAO, 2006a), of which at least 1,450 million tonnes can be estimated to be used as animal feed. Each tonne of cereal can be modestly estimated to contain 3 million kcal. This means that the yearly use of cereals for non-food use represents 4,350 billion kcal. If we assume that the daily calorie need is 3,000 kcal, this will translate into about 1 million kcal/year needed per person. From a calorie perspective, the non-food use of cereals is thus enough to cover the calorie need for about 4.35 billion people. It would be more correct to adjust for the energy value of the animal products. If we assume that all non-food use is for food producing animals, and we assume that 3 kg of cereals are used per kilogram animal product (FAO, 2006b) and each kilogram of animal product contains half the calories as in one kg cereals (roughly 1,500 kcal per kg meat), this means that each kilogram of cereals used for feed will give 500 kcal for human consumption.
One tonne cereals used for feed will give 0.5 million kcal, and the total calorie production from feed grains will thus be 787 billion kcal. Subtracting this from the 4,350 billion calorie value of feed cereals gives 3,563 billion calories. Thus, taking the energy value of the meat produced into consideration,the loss of calories by feeding the cereals to animals instead of using the cereals directly as human food represents the annual calorie need for more than 3.5 billion people.