Environmental Engineering Reference
In-Depth Information
Box 12.1
Calculating Global Anthropomass in the Year 2000
When calculating the total mass of humanity, it is imperative to take into account
substantial differences in age compositions of the constituent populations and the
disparities in their average body weights. Low-income countries have much higher
shares of children and young teenagers (whose average body weights are fractions
of the typical adult mass) than do afl uent countries. For example, in 2010, 40% of
Africa's population was younger than 15 years, and the continent's median age was
19.7 years, while the corresponding numbers for Europe were 15% and 40.2 years
(UN 2011). The great economic divide is also rel ected in average body weights: i ve-
year-old children in the United States are 3-4 kg heavier than in India, and by the
age of 15 the difference is twice as high (Ogden et al. 2004; Sachdev et al. 2005). But
national means differ even within the same economic group. Most notably, in 2005
the average obesity rates (dei ned as a body mass index higher than 30) were as low
as 3.9% in Japan and as high as 33% in the United States, with the European shares
ranging from 10% in Italy to about 23% in England (NOO 2009).
That is why, in calculating the global anthropomass in the year 2000, I have used
four different weighted means of body averages: for North America with its overweight
population of more than 300 million people; for all the other high-income countries
(about 800 million, dominated by Europe); for modernizing nations (4.2 billion, domi-
nated by China and India); and for the world's poorest economies (about 700 million,
mostly in Africa). Age and sex structures are available for these four population catego-
ries (UN 2011), and I used average body masses derived from anthropometric studies
and growth curves for populations of four representative countries, the United States,
Germany, China, and India (Schwidetzky, Chiarelli, and Necrasov 1980; Sachdev et al.
2005; Zhang and Wang 2010). This procedure resulted in a weighted mean of about
50 kg, which means that the total live weight of the global anthropomass of 6.1 billion
people was about 300 Mt in the year 2000. With human body water content averaging
60% (Ellis 2000) and with 45% of carbon in the dry mass, that total yields about 55
Mt C. In contrast, Barnosky (2008) used an average live weight of 50 kg up to about
400 years ago, and 67 kg afterwards, both being clear exaggerations.
also produce specii c rates for some surprising comparisons of biomass densities,
which must start with calculating the global anthropomass.
Because better diets (brought about by the dietary transitions of the late nine-
teenth and twentieth century) have resulted in higher average body weights—for
example, Japanese records show that average male weight at age 20 rose from 53
kg in 1900 to 65.4 kg in 2000 (SB 2010)—the total biomass of our species has risen
at a faster rate than did the overall population, which was about 3.7 times greater
in 2000 than it was in 1900. Using the weighted global body mass mean of 45 kg
and an approximate population total of 1.65 billion results in 13 Mt C in human
