Environmental Engineering Reference
In-Depth Information
There were also more than 14 billion chickens and about 1.7 billion other birds
(ducks, turkeys, geese). Even if no more than about half of all feedstuffs came from
concentrates and average feeding efi ciencies were fairly high—feed/product conver-
sion ratios of 1:1 for milk, 4:1 for poultry meat and eggs, 8:1 for pigs, and 10:1 for
cattle—the global requirement would be no less than 1.3 Gt of grain equivalent.
For comparison, the FAO's (2011b) balance sheets show about 38% of all cereals,
24% of all tubers and pulses, and 10% of all oilseeds were fed directly to livestock;
adding to this cereal milling residues and oil cakes results in a total grain equivalent
of nearly 1.3 Gt, an excellent coni rmation of the just presented estimate. Producing
this feed would have required, even with a relatively high average yield of 2.5 t/ha,
some 520 Mha of arable land, or no less than a third of the total cultivated area in
the year 2000 (see also Steinfeld et al. 2006). Although higher intakes of animal
foods were a key component in the early stages of the modern dietary transition
they had, at least until the 1940s, resulted in only limited demand for new arable
land, and other key ingredients of the changing dietary composition were more
important.
These included a higher consumption of sugar and plant oil, as well as a greater
variety of vegetables and fruits. Per capita sugar consumption was minuscule in all
traditional societies. It began to rise with production from cane plantations (i rst in
the Caribbean, later also in Africa and Asia as well as in Hawaii and a few southern
U.S. states), and in temperate latitudes it took off only with a large-scale commercial
extraction from beets during the nineteen century. Plant oils began to compete with
animal fats, and rising incomes created a demand for better-quality vegetables and
fruits. At the same time, staple grain and tuber intakes declined, and legumes saw
an even greater reduction. All of these trends got under way in parts of Europe and
North America before the end of the nineteenth century, and after World War II
they spread to Latin America and Asia.
