Maize, Zea mays, is an important food crop for human consumption and for feeding to animals. Two varieties of maize are MON810 and Justina. Justina has been developed in the traditional way by selective breeding (artificial selection) and MON810 is an example of a genetically modified (GM) organism. Countries vary in the extent to which they grow GM varieties such as MON810, instead of traditional varieties such as Justina. • In the USA, 88% of the total maize that is grown is GM. • In most European countries, 0% of the maize that is grown is GM. Scientists used computer models to predict the effect of two different changes in agricultural practice on maize crop yields: a global ban that reduces the cultivation of GM maize to 0% everywhere all countries increasing the cultivation of GM maize to the 88% level of the USA. Table 6.1 shows the results of this modelling for four countries. [Table 6.1]