Sustainable Agriculture and Food: Four volume set (Earthscan Reference Collections)

20 The Global Food System

through its consumption of energy produced by fossil fuel burning. For each kilo-
gramme of cereal from modernized high input conditions, 3–10MJ of energy are
consumed in its production; but for each kilogramme of cereal from sustainable,
low input farming, only 0.5–1MJ are consumed. A shift to low input systems
could, therefore, have an impact on the process of global warming.
However, there is considerably more energy consumed between the farm and
the consumer. In the US, it is said that food travels on average 3000km from farm
to plate. In Britain, the production of a 1kg loaf of bread consumes some 20.7MJ
(equivalent to 0.48kg of oil), of which 80 per cent is consumed by milling, baking,
transport and retailing (Leach, 1976). Making agriculture more energy efficient,
by transferring to low input sustainable processes, could only decrease the energy
consumed in the remaining 20 per cent. This could reduce the energy consumed
in a loaf of bread to 16–17MJ. However, for cereals processed and consumed on
the farm, or those passing through fewer processing or transport stages, significant
improvements in energy efficiency could be possible following a transition to a
more sustainable agriculture.

Pesticide-induced pest resistance and resurgences

The reason for applying pesticides is to prevent pest damage, yet unfortunately
they can cause outbreaks themselves. Pesticides can be inefficient for several rea-
sons (Conway, 1971; Risch, 1987). They can cause resurgences by killing off the

Table 1.2 Amount of cereal produced (kg) per megajoule (MJ) of direct energy input

different agricultural systems

Location System of production No. of kg cereal produced per

MJ of direct energy (+ indirect

energy for fertilizers and

pesticides used (kg/MJ)

Japan Irrigated, high input rice 0.30

China Organic rice 1.53

Philippines High input, irrigated rice 0.22–0.36

Low input, irrigated rice with Azolla 0.79

Rainfed, upland rice 0.72–0.88

Latin America Low input, upland rice 1.94

Bangladesh Low input, deepwater rice 2.64

USA High input, irrigated rice 0.09

USA High input maize 0.25

Low input maize, alternative rotations 0.67

UK Very high input wheat 0.45

Low input wheat 1.09

Sources: Adapted from IRRI, 1981; FAO, 1976; Walters, 1971; Pimentel et al, 1989; Leach, 1985