7. Summary: concluding remarks

The Japanese case of the reduction of paddy field area and its consequences are quickly reviewed. Japan had tried to establish complete self-sufficiency of rice historically, especially after the World War II. And then, it is finally realized in the 1960s, after long development investigation for improvement of paddy cultivation and fields including farming techniques

Just after the reach to complete self-sufficiency, it had faced to the problem of over production of rice, which was caused by higher yield of rice, reduction of rice consumption with increased consumption of other food, including bread, meat as well as vegetables. The government asked farmers to convert their farm fields from rice to other crops with some portion of their farming plots, providing some subsidies. The rapid industrialization and urbanization also require paddy fields in the plain to be transferred to urban use. Consequently, the area of rice cultivation area has been decreasing as from about 3.3 million ha in 1960 to 1.56 million ha in 2017. It is a drastic reduction (Figure 2). During the same period, the rice consumption per capita per year of Japan has drastically reduced from about 127 to about 68 kg (Figure 3) [19]. With these changes, it could be easily recognized that the water ponding area, that is temporal water body or wetland, has reduced to the half of the peak, and the hydrological environment has been affected. It also means the degradation of multifunction of paddy fields. The wildlife is losing their habitats, and the biodiversity and the ecosystem developed historically have

In Japan, another problem is a reduction of farmers and their successors, which is another constraint to conserve paddy areas. The reduction of paddy fields means not only reduction of

and infrastructures of it.

154 Irrigation in Agroecosystems

Figure 2. Changes of paddy cultivation area in Japan (source: [9, 19]).

been modified.

In this chapter, implication of paddy cultivation and paddy fields is reviewed, focusing on flooding in the fields including its reasons and consequences.

It is clear that paddy fields, paddy cultivation, and paddy irrigation need much water, land reclamation and preparation, and system to distribute water. Therefore, they have developed infrastructure, institution as well as interconnectedness of the farmers and other stakeholders.

Significance of paddy fields as the artificial, temporal/seasonal wetland is to be assessed in comprehensive manner with aspects of agriculture, eco-environment, and hydrology. Since they use much water and might alter the local water balance and ecoenvironmental system with adverse effects, they are to be arranged appropriately in the hydrological and environmental regime of the region. Local communities established with paddy fields are to be organized continuously as the base for the society and culture and the potential to manage the future changes of environments.

In addition, it is urgent to reevaluate the role and implication of paddy cultivation and fields in the local system under the changing climate.

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