Currently some 14 million km2 of the earth’s surface (approximately 10%) is used for agriculture. This proportion can no longer be substantially increased without taking massive ecological risks and without enormous investment of capital, technical innovation and energy. The gigantic areas taken up by tundras, deserts, savannas, bushlands and tropical rainforests are hardly suitable for productive agriculture. Furthermore, everywhere in the world considerable areas of potential agriculture are sacrificed for human settlements and to develop infrastructure (roads and tracks for railways). Even larger areas are irreversibly lost for agriculture and forestry because of incorrect treatment, such as deforestation, overgrazing, salinisation, contamination or erosion. As the human population is still increasing exponentially (1830: 1 · 109; 1930: 2 · 109; 1960: 3 · 109; 1990: 5.4 ·109; 2000: 6.5 · 109), the agriculturally usable area per capita is continuously reduced (1980: 0.30 ha · head−1; 2000: 0.22 ha · head−1).
KeywordsBiomass Chlorophyll Income Assimilation Photosynthesis
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