The Environmental and Social Costs of Improvement 171991). Water systems have become increasingly contaminated. Nitrate in water
can give rise to the condition methaemoglobinaemia in infants and is a possible
cause of cancers. Pesticides contaminating water can harm wildlife and exceed
drinking water standards. Nitrates and phosphates from fertilizers, and organic
wastes from livestock manures and silage effluents all contribute to algal growth in
surface waters, deoxygenation, fish and coral deaths, and general nuisance to lei-
sure users. Eroded soil also disrupts watercourses, and run-off from eroded land
causes flooding and damage to housing, irrigation systems and natural resources.
Various pollutants also harm farm and local natural resources. Pesticides damage
predator populations and other wildlife and induce resistance in target pests. Nitrates
from fertilizers and ammonia from livestock waste disrupt nutrient-poor wild plant
communities. Metals from livestock wastes raise metal content of soils, and patho-
gens in wastes can harm human and livestock health. The atmosphere is contami-
nated by ammonia, which plays a role in acid rain production; nitrous oxide derived
from fertilizers, which plays a role in ozone layer depletion and global warming; and
methane from livestock and paddy fields, which also affects global warming.
The consumer is most likely to be directly affected by eating food contami-
nated mainly by residues of pesticides, but also by nitrates and antibiotics. In the
industrialized countries, the levels of pesticides in foods have been falling steadily
since the 1950s (Conway and Pretty, 1991; WPPR, 1994; Gartrell et al, 1986a,
1986b). Nonetheless, there are occasional public scares over particular products
and rare incidents of severe poisoning arising from the spraying of illegal products.
But in developing world countries, daily intakes are often very high. These may be
in cereals, such as in India (Kaphalia et al, 1985; Sowbaghya et al, 1983); in fish,
such as from rice fields in Malaysia (Chen et al, 1987) or lakes and rivers of Kenya,
Nigeria and Tanzania (Atuma, 1985; Atuma and Okor, 1985); and in milk from
cows affected by spray drift from cotton plantations in Nicaragua and Guatemala
(ICAITI, 1977).
But the major hazard lies in locally marketed food. Leafy vegetables are often
sprayed twice a week and may come to market with a high degree of contamina-
tion, especially in the dry season. Over 50 per cent of green leafy vegetables col-
lected around Calcutta during the dry winter months contained residues, though
this fell to 8 per cent in the wet season (Mukherjee et al, 1980). In Indonesia, cab-
bages and mustard greens have been found to contain organophosphates many
times in excess of human tolerance limits (Darma, 1984). Similar levels of con-
tamination have been recorded from Africa (Atuma, 1985).
These costs of environmental damage are growing, and are dispersed through-
out many environments and sectors of national economies. For a comprehensive
review of the effects of agricultural pollution on natural resources, wildlife and
human health see Conway and Pretty (1991). What has characterized recent anal-
yses has been the recognition that farmers themselves are suffering declining
incomes or health effects from these modern approaches to agriculture. The fol-
lowing sections consider the issues of energy consumption by agriculture, pest
resistance and resurgences, health impacts of pesticides and soil erosion.