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such as Bangladesh, Egypt and Vietnam (FAO 1991). Besides
salinization, acidification, the concentration of ground-level
ozone and the increase in intensity of ultra-violet radiation are
also blamed for causing chemical and biotic stresses to crops.
According to Brown (1990), about 4 million tonnes of grain are
lost per year due to chemical and biotic stresses.
Ecosystem degradation, such as groundwater pollution, soil
erosion, salinization and loss in biodiversity, is also blamed for
the failure of most farming systems to reach the potential ceiling
of most animal and crop varieties. Although the difference
between farm yields for cereals and genetic yield potential
is closing (Peltonen-Sainio
et al.
2008; Cassman 1999), the
majority of farmers produce cereal yields that are far below
genetic potential. Irrigated wheat, rice and maize produce as
much as 80 per cent of potential yield, while rain-fed agriculture
produces less than 50 per cent of potential yield (Lobell
et al.
2009). While this suggests that there is room for greater yields,
it also points to losses in potential food production.
Declines in food production are also caused by the loss of
ecosystem services such as pollination, which is essential
to food crop production. Clara Nicholls
et al.
(2013) estimate
that 35 per cent of global crop production depends on animal
pollination. However, looking at mango production as a case, the
population of pollinators is declining due to cropland increases,
which isolate crop fields from insect and animal habitats
(Carvalheiro
et al.
2012), as well as the use of insecticides
(Alaux
et al.
2010; Gill
et al.
2012). Pollinator-dependent
crops include alfalfa, sun ower, fruits and vegetables (Spivak