"...mein Acker ist die Zeit", Aufsätze zur Umweltgeschichte - Oapen

City and Nature (2007)
only) was considerably below that of an average temperate European forest (15
kg/m 2), as are all values calculated for cities in history (see Table 5). We must not
forget that within this estimation humans are at the summit of the food pyramid. A
basic principle of general biology teaches that biomass is reduced from one stage in
the food pyramid to the next by roughly a factor of 10. Thus our estimate ends
within an order of magnitude of less than two pyramid stages with respect to the
human population in medieval Florence, if it is compared with the productivity of
the temperate European forest. Such values for cities seem indeed still comparatively
high given the fact that city ecosystems are not primary producers, although
they do concentrate the biomass production of huge hinterland areas.
Table 5. Human Biomass Ratios per Square Meter of City Area for Selected Cities.
CITY YEAR HUMAN
BIOMASS
RATIO [KG/M 2]
Florence* 1250 0.8
Paris 1365 2.9
Paris 1637 4.3
Paris 1700 2.0
Paris 1784 0.8
Paris 1796 0.7
Paris 1856 1.5
Paris 1921 1.2
Paris 2000 1.0
London 1901 0.6
Buenos Aires 1991 5.2
Kolkata (by Indian Gov.) 1991 1.3 [?]
Los Angeles 2000 0.16
Berlin 2000 0.2
London 2000 0.2
Mexico City 2000 0.2 [?]
New York 2000 0.5
Tokyo 2000 0.6
Delhi 2001 0.4 [?]
Note: The calculations are based on density data provided by Demographia; average resident weight
assumed with 50 kg for contemporary cities; 45 kg for London in 1901 and Paris until 1856; 40 kg for
Florence 1250; 40 kg for Buenos Aires, Delhi, Kolkata, Mexico City. The numbers for Kolkata,
Mexico City, and Delhi likely to be underestimates, although originally taken from government
sources. – * data from Benevolo
Our approach offers a surprise. The numbers for human biomass per area appear
counterintuitive, as one would expect higher human biomass concentrations in
towns correlated to increased world, continent, country populations and an increased
degree of urbanization. But it seems that times of prime densities are al-
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