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population growth, the second one was a much more common reliance on more
powerful draft animals, and the third one was a gradual improvement in typical
diets, particularly manifesting in higher intakes of animal foodstuffs. During the
eighteenth century, annual population growth rates in Europe were on the order of
0.4%, and during the nineteenth century they rose to around 0.7%, the latter rate
being an order of magnitude higher than typical medieval rates. North American
rates, thanks to immigration, were even higher, well above 2% after 1850.
The earliest use of draft animals called for only a limited expansion of phyto-
mass harvests. Oxen used for i eld work in ancient Egypt or in Roman and medieval
farming subsisted on readily available roughages (cereal straws, any accessible
grazing) and hence did not require any additional land for feed crop cultivation
and did not lower the potential grain supply of peasant families. This changed
only when better-off farmers in Atlantic and Central Europe began using more
powerful but also more demanding horses. By the early nineteenth century a pair
of average European horses would need nearly 2 t of feed grain a year, a mass
about nine times that of the total food grain consumed annually by their master.
And the cultivation of North American grasslands led to an even greater demand
for animal feed.
At the beginning of the twentieth century a team of dozen powerful horses used
for i eld work in the grain i elds of Dakotas or Manitoba needed about 18 t of oats
and corn per year, about 80 times the total amount of food grain consumed by their
owner. Obviously, only land-rich countries could afford this burden: growing con-
centrate feed for those 12 horses would claim about 15 ha of farmland. This would
have been an excessive burden even in the land-rich United States, where by 1900
an average farm had almost 60 ha, but only a third of it was cropland. As a result,
only large grain growers on the Great Plains could feed a dozen or more horses,
and the countrywide ownership averaged only three horses or mules per farm (USBC
1975). Expansion of the cultivated area and the mechanization of i eld work (includ-
ing the use of horse-drawn combines, some pulled by more than 30 animals) brought
an unprecedented demand for feed crops, which eventually added up to a quarter
of America's harvested land (box 8.5).
Outside North America, agricultural mechanization powered by draft animals
proceeded at a much slower pace, and in some of the world's poorer regions it relied
only on less demanding water buffaloes (in most of Asia's rice-producing countries)
and oxen. The third important reason for the expansion of farmland was a gradual
improvement in average diets: after centuries of basic subsistence typical food
intakes began to include more animal foodstuffs, whose production required a
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