Optimising land use and consumption of livestock products in the human diet

The projected increase in demand for food, due to increased population size and consumption of animal protein, has raised concerns about the expansion of agricultural land worldwide. Limiting global land expansion for food production requires insight into competition between humans and animals for land. Our objective was to identify the relationship between land use and the importance of animal protein in the human diet. We determined the minimum amount of land required to feed a growing population a diet varying in the percentage of protein derived from animals. The agricultural system in the Netherlands was used as an illustration, assuming no import and export of feed and food. The population ranged from 15 million (close to the current population size) to the maximum number of people that could be supported by the system. Human diets varied in the percentage of protein derived from animals between 0 to 80%. Land use requirements were determined for cultivation of food and feed crops, and grass. For production of animal protein, our optimisation model could choose between meat and milk produced by dairy cows and pigs. We demonstrated that land is used most efficiently if people consume small amounts of animal protein, i.e. 15% of protein derived from animals (% PA), especially from milk. The role of animals in such a diet is to convert by-products from arable production and the human food industry, into protein rich milk and meat. Below 15% PA, human inedible products are wasted, whereas above 15%, specific feed crops will have to be cultivated.
Our results contradict LCA studies that suggest that vegan diets require the least amount of land. These LCA studies do not include competition for land between humans and animals. Accounting for competition for land and land suitability requires a systems approach to optimize land use for its various functions. Integration of crop and animal production in optimisation modelling illustrates that, if people consume small amounts of animal protein, animals reduce land requirements for food production by converting by-products into protein rich milk and meat. Both high and low consumption of animal protein reduces land use efficiency.