Paddy Field Characteristics in Water Use: Experience in Asia - Water and Agriculture: Sustainability, Markets and Policies - page 229

The above-mentioned total paddy irrigation and drainage system creates an excellent
secondary natural environment with a rich flora and fauna, and water taken from a river
to the system preserves another and richer ecosystem outside the river. Paddy farming
embraces varied on-farm water management such as for puddling, transplanting,
temporary dry-up, intermittent irrigation and harvesting. This provides an ideal habitat for
creatures which used to inhabit flooded plains, marshes and swamps. Note that an
environment moderately intervened by human activity is actually helpful to less
competitive creatures because the propagation of more competitive ones is disturbed by
human intervention. Such a phenomenon is widely observed in a natural habitat
intervened by occasional flood and dry-up. Figure 20 shows an example of a paddy rice
cultivation calendar with typical variations of on-farm water management.
Figure 20. Example of paddy rice farming calendar with typical variation
of on-farm water management
Source : Ministry of Agriculture, Forestry and Fisheries, Japan , 2005.
3.4 Enriching ecosystems and bio-diversity in and surrounding paddy fields
Suzuki (2004) reported the results of field research on fish swimming upstream and
downstream in drainage canals connecting paddy fields in Japan. Misgurunus
anguillicaudatus , a species of loach, and Carassius spp., i.e. crucian carp, swim up in
drainage canals to paddy fields where they grow, then swim down from paddy fields after
propagation. The on-site survey was conducted throughout a year. Table 6 shows the
results of estimated biomass of loach in several paddy fields. It indicates that the loach
increase their wet weight on average by three and half times from the time of their
swimming up to nine paddies surveyed. It is also reported that the crucian carp increase
their wet weight by 9.6 times from the time of their swimming up to a paddy.
Japan has about 38 million ha of national land territory of which rice paddy fields
account for only about 7%, or 2.6 million ha. A large number of various animals and
plants including endangered species survive in this rather small paddy area. The Ministry
of Agriculture, Forestry and Fisheries (MAFF) of Japan (2003) carried out an on-site
survey on fish, reptiles and amphibians, and their predators — birds, mammals, benthos,
dragonflies and plants — surviving in paddy fields and canals in Japan. Table 7 shows the
total number of species in 14 areas verified in “Survey for developing environmental
information in agriculture and rural areas” conducted by MAFF. It indicates that more
than 30% of species of fish and dragonflies in the national territory survives in paddy
fields and canals in the surveyed 14 areas, and more than 20% of species of reptiles,
amphibians and plants in the national territory survives there. Furthermore, large numbers
of endangered species designated by the Ministry of Environment and prefectural
governments are discovered in paddy fields and canals.