4.1 Introduction
For centuries, rotational swidden agriculture aimed at fulfilling household food
needs has been the dominant form of agriculture in the mountainous areas of
Thailand and Vietnam. Nowadays, this form of agriculture is difficult to find, as
households are increasingly growing crops in permanent fields for their own food
needs as well as for sale (Chap. 1). The process of agricultural intensification and
commercialization has been accompanied by a change in the types of crops grown
and the cultivation methods used, with a greater reliance on external inputs such as
fertilizers and pesticides (Pingali 2001).
The increasing importance of crop protection can partly be explained by the
increased pest pressure that has accompanied more intensive land use, and also the
fact that farmers have a greater economic incentive to reduce crop damage as land
productivity increases. For instance, surveying weed infestations across 12 maize
fields with steep slopes in north-western Vietnam, Wezel (2000) found that shorter
fallow periods were associated with higher levels of weed infestation, a major
concern for farmers as these infestations reduced maize yields and required much
labor to resolve, with farmers spending as much as 35 to 50 days weeding one
hectare of maize.
The problem is that the increasing demand for better crop protection is almost
solely met through an increase in the use of synthetic pesticides. Studying pesticide
use in Yunnan and Guizhou in China, Xu et al. (2008) explained that the dependence of farmers on synthetic pesticides is due to the fact that farmers find
pesticides easy to use and that they provide a rapid means of controlling pests,
plus that there is limited knowledge among farmers and consumers about the risks
of using such pesticides. Added to this, the policy framework in place encourages
their use. All of these factors apply across Southeast Asia countries in general.
However, it has long been known that pesticides may be transported to environmental compartments far from their site of application, where they may severely
affect non-target organisms, pollute surface and ground water, and enter the human
food chain. This fact has stimulated much interest among scientists and policy
makers about the issue of pesticide exposure and has led to a fundamental debate
about the role of pesticides in our food system. As a consequence, numerous studies
have been conducted worldwide on the fate and behavior of pesticides in agricultural areas, with the pollution of surface waters receiving particular attention.
There have been numerous studies carried out into pesticide use and risk exposure
in Southeast Asia, but almost all of them have focused on lowland areas and chiefly
paddy rice systems, which represent the main type of agricultural land use in these
areas and which are essential for maintaining food security in the region
(e.g., Dasgupta et al. 2007). Much less is known about the environmental exposure
of using agricultural pesticides in mountainous areas and the effects they have on
peoples’ health, though several studies carried out in northern Thailand have pointed
to very significant health hazards (Stuetz et al. 2001; Kunstadter et al. 2006).
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M. Lamers et al.
For centuries, rotational swidden agriculture aimed at fulfilling household food
needs has been the dominant form of agriculture in the mountainous areas of
Thailand and Vietnam. Nowadays, this form of agriculture is difficult to find, as
households are increasingly growing crops in permanent fields for their own food
needs as well as for sale (Chap. 1). The process of agricultural intensification and
commercialization has been accompanied by a change in the types of crops grown
and the cultivation methods used, with a greater reliance on external inputs such as
fertilizers and pesticides (Pingali 2001).
The increasing importance of crop protection can partly be explained by the
increased pest pressure that has accompanied more intensive land use, and also the
fact that farmers have a greater economic incentive to reduce crop damage as land
productivity increases. For instance, surveying weed infestations across 12 maize
fields with steep slopes in north-western Vietnam, Wezel (2000) found that shorter
fallow periods were associated with higher levels of weed infestation, a major
concern for farmers as these infestations reduced maize yields and required much
labor to resolve, with farmers spending as much as 35 to 50 days weeding one
hectare of maize.
The problem is that the increasing demand for better crop protection is almost
solely met through an increase in the use of synthetic pesticides. Studying pesticide
use in Yunnan and Guizhou in China, Xu et al. (2008) explained that the dependence of farmers on synthetic pesticides is due to the fact that farmers find
pesticides easy to use and that they provide a rapid means of controlling pests,
plus that there is limited knowledge among farmers and consumers about the risks
of using such pesticides. Added to this, the policy framework in place encourages
their use. All of these factors apply across Southeast Asia countries in general.
However, it has long been known that pesticides may be transported to environmental compartments far from their site of application, where they may severely
affect non-target organisms, pollute surface and ground water, and enter the human
food chain. This fact has stimulated much interest among scientists and policy
makers about the issue of pesticide exposure and has led to a fundamental debate
about the role of pesticides in our food system. As a consequence, numerous studies
have been conducted worldwide on the fate and behavior of pesticides in agricultural areas, with the pollution of surface waters receiving particular attention.
There have been numerous studies carried out into pesticide use and risk exposure
in Southeast Asia, but almost all of them have focused on lowland areas and chiefly
paddy rice systems, which represent the main type of agricultural land use in these
areas and which are essential for maintaining food security in the region
(e.g., Dasgupta et al. 2007). Much less is known about the environmental exposure
of using agricultural pesticides in mountainous areas and the effects they have on
peoples’ health, though several studies carried out in northern Thailand have pointed
to very significant health hazards (Stuetz et al. 2001; Kunstadter et al. 2006).
150
M. Lamers et al.