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

26 The Global Food System

Table 1.3 Net benefit and health costs of four pest management strategies in lowland

irrigated rice, Philippines

Pest management strategy Net benefits, excluding

health costs (Pesos/ha)

Health costs

(Pesos/ha)

Complete protection: nine applications of

pesticide per season

11,846 7500

Economic threshold: treatment only when

threshold passed, usually no more than

two applications used

12,797 1188

Natural control: pest control emphasizes

predator preservation and habitat

management, alternative hosts and

resistant varieties

14,009 0

Current local practice: 2–3 applications of

very hazardous compounds per season

13,847 720

Source: Rola and Pingali, 1993

Soil Conservation and Erosion

The causes and costs of erosion

Despite the fact that indigenous systems of soil and water conservation are wide-
spread, well adapted to local conditions, persist for long periods and are capable of
supporting dense populations, soil erosion continues to be a problem throughout
the world (UNEP, 1983; Reij, 1991; Kerr and Sanghi, 1992; Tato and Hurni,
1992; Hudson and Cheatle, 1993; Pretty and Shah, 1994). Indigenous systems are
insufficient alone to prevent agricultural land from continuing to lose productive
soil, water and nutrient resources. This is partly because not all farmland is pro-
tected by conservation measures, but also because not all erosion arises from farm-
land. Both roads and urban areas concentrate water flows and non-agricultural
areas are also subject to erosion.
Farmers may not be conserving soil and water for a variety of reasons. They
may lack the locally appropriate knowledge or skills, particularly if they have been
resettled or migrated to new areas. They may be unwilling to invest in conserva-
tion measures if the economic costs of conservation are greater than the expected
benefits, particularly if the future is uncertain, such as if political instability or
conflict threaten the future, or if security of tenure is uncertain. Farmers may be
short of labour for construction or maintenance, such as following a decline in
population, outmigration in the face of better opportunities for income earning,
particularly in urban centres, or simply rising labour costs. They may not be con-
serving because of the misguided efforts of earlier soil and water conservation pro-
grammes. Finally, they may be so responsive to policies encouraging increased food
production that they simply ignore the costs.