It is often asserted (see, for example, Borlaug, 1999) that thanks to increases in yield, land has been saved with diminished pressure on the envi­ ronm ent as a result, such as less deforestation than otherwise would have taken place. To take cereals as an example, the reasoning is as follows. If the

average global cereal yield had not grown since 1961/63 when it was 1 405 kg/ha, 1 483 million ha would have been needed to grow the 2 084 million tonnes of cereals produced in the world in 1997/99. This am ount was actually obtained on an area of only 683 million ha at an average yield of 3 050 kg/ha. Therefore, 800 million ha (1483 minus 683) have been saved because of yield increases for cereals alone. This conclusion should be qualified, however; had there been no yield growth, the most probable outcome would have been much lower production because of lower dem and resulting from higher prices of cereals, and

somewhat more land under cereals. Furthermore, in many countries the alternative of land expansion instead of yield increases does not exist in practice.