There is little doubt that the United States can supply its own basic food needs into the indefinite future and its obligation to supply the rest of the world is not unlimited. But even if there is a very high level of foreign demand, capital and technology (and perhaps even labor!) still can substitute for land; there is no fixed relationship between land and output. Nevertheless, the public still tends to see land availability

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as the main determinant of agricultural capacity; the scientific revolution's effects on agriculture are still relatively new.