The Environmental and Social Costs of Improvement 19In industrialized countries the trend has been towards the substitution of inexpen-
sive fuel energy for expensive human labour, so making agriculture a significant
energy consumer. Since the 1940s, some 25 million draft animals and 9 million
agricultural workers have been replaced in the US; and in the UK, 340,000 jobs
have been lost (Berardi, 1978; MAFF, passim). Energy consumption has increased
too. According to the OECD (1993), the absolute energy consumption per hec-
tare has increased in OECD countries by 39 per cent from 1970 to 1989. On
average, some 1734MJ are consumed per hectare of agricultural land, rising to
46,400MJ for the highest consumer, Japan.
One consequence of this increased substitution of energy for labour in agricul-
ture is a growing contribution to global warming. Agriculture is a major direct source
of atmospheric pollution, emitting methane, nitrous oxide, ammonia and the vari-
ous products of biomass burning (Conway and Pretty, 1991; IPCC, 1990). The
single main cause of global warming, however, is carbon dioxide, estimated to con-
tribute about half of the projected warming over the next 50 years. Agriculture con-
tributes to CO 2 production directly through the burning of biomass and indirectly
Table 1.1 Impact of modernization of agricultural systems on yields and direct energy
consumptionCountry Low input
comparisonHigh input
comparisonAmount of
extra yield
for high inputAmount of
extra energy
consumption
for high input
Philippines^1 Traditional rice Modern rice +116% +3000%
Rainfed rice Irrigated rice +150% +800%
Irrigated rice Irrigated rice
with Azolla with N +0–30% +200%
India2* Bullock, rice Power tiller, rice +8% +43%
Bullock, rice Tractor, rice +13% +74%
Bullock, wheat Power tiller, wheal +12% +89%
Bullock, wheat Tractor, wheat +6% +266%
India3* Bullock, rice Mechanized, rice +20% +45%
Bullock, wheat Mechanized, wheat +29% +138%
US^4 Low input, maize Conventional, maize +0% +120%
US^5 Organic, wheat Conventional, wheat +29% +48%
US^4 Low input, maize Conventional, maize +0% +22%Note: For the sake of comparisons, the data in this table refer to direct energy use plus indirect
energy for manufacturing fertilizers and seeds. These are not comprehensive energy accounts,
in which all embodied energy is included. For those marked *, only direct energy is included. 1
Luzon 2 West Bengal 3 Uttar Pradesh 4 Midwest 5 Pennsylvania and New York.
Sources: FAO, 1976; Leach, 1976; Singh and Singh, 1976; Pimental et al, 1989; Berardi, 1978;
Ikerd et al, 1992