Peering forward from the beginning of the twentieth century, a writer would have examined Figure 7.2.1 and Figure 7.5.3--but only up to 1900. The writer would have projected more of the slow trend evident to 1900. He might have anticipated the freeing of cropland as petroleum replaced timothy for draft power. But the jump in yields in Europe and North America from 1940 on would have surprised him. The Green Revolution would have surprised him more.
In Figure 7.3.2, I project a rise of yields but at a declining rate and only to a ceiling set by crops already grown. This projection assumes that societies will continue encouraging, scientists will continue discovering, and farmers will continue venturing toward that ceiling. Disorder from Dushanbe and Sri Lanka via Mogadishu and Sarajevo to Port-au-Prince and Managua renders encouragement by some nations hopeless. A decline of money means declining agricultural research. So a surprise could arrest the trend of Figure 7.3.2.
Not all surprises are unhappy. It is optimistic but rational to hope that some breakthrough will become practice before ten billion arrive, surprising me as the data after 1900 would have surprised Malthus and even the writer at the turn of the century. The distance between average yields and the actual, not theoretical, 21 t/ha grain in Pasco, Washington provides room for a surprise. One can even visualize how the surprise might be caused: Genetic engineering transferring genes from the Pasco maize to other crops. The surprise likely would dislocate farming and displace farmers as changes have, rapidly and cruelly, since 1940. But the surprise would spare more land for Nature.