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If we call a significant yield increase in single crops a ‘green revolution’, then the first green revolution took place about 10 000–12 000 years ago, when humans started to cultivate land. This was also the beginning of civilization. Since then, humans have increasingly transformed the land and natural vegetation and have risen to be the main creators of the biogeosphere. Today, there is hardly any ecosystem around the globe that has not been influenced by humans. It was only in 1930 that the world population reached 2 billion, and since then it has increased to 6 billion in the year 2000. Because of this rapid increase, the demand for food, feed and industrial crops has grown enormously. Half of the 1.5 billion ha of arable land – 18 % of the biologically productive land area of the earth – was first cultivated only in the 20th Century, and mostly forest was sacrificed to meet this requirement. The second green revolution started only in the late 1960s when high-yielding varieties of wheat and rice were designed to overcome the predicted hunger crisis. Great achievements were made, especially in relation to irrigated agriculture, while rain-fed farming was hardly affected by this revolution. World agriculture today faces two major constraints to which not enough attention is paid by scientists and decision makers. First, we increasingly restrict our food basis to a limited number of plant species. Today, 65 % of the world's arable land is reserved for only 21 annual crops. Even more worrying is the fact that 60 % of our food energy and protein comes from only three cereals – wheat, rice and corn. Designing ‘functional’ food using gene technology to improve food quality, for example in rice, will speed up this process of constriction since diversified ingestion is no longer necessary to meet the daily required balance of food types. Secondly, arable land resources are under-utilized because of poor management. Yields of rice, for example, are below the world average of 3.8 t ha(−1) (1998) in 70 countries. If those countries achieved only the average level for their continent, for example 2.2 t ha(−1) in Africa, world rice production could be increased by 17 %. There is a need to invest in better management of arable land to prevent further loss in productivity and simultaneously to investigate under-explored plants to broaden our future food basis.
