The world population has increased four-fold during the 20th century from about 1.5 billion to 6.1 billion. Recently, the population in developed countries became constant, however, the population is consistently increasing in developing countries, and the world population in 2050 is estimated to be 9.0 billion. Therefore, sufficient supply of food to support an increasing population is essential at the global scale as well as for each country. During the 20th ...
