Plant Resources for Food and Fibre
Human diets are predominantly based upon direct consumption of plants. Animal products are a smaller part of most human diets, but tend to be consumed in greater quantities by more affluent human populations. Animal production is supported by the growth of plants as feed, often consumed by the animal as pasture or fodder or in more intensive production systems as grain. The production of food in animals is relatively inefficient. For example, it takes 3000 litres of water to produce 1kg of rice but 15,000 litres of water to make 1kg of beef, because more than 10kg of feed is needed to produce the 1kg of beef (Millstone and Lang, 2008).