Diversity of Biota in Rice Paddies and Adjacent Areas
— Clarifying the Impact of Farming Activities on the Biota and its Diversity in Rice Paddies and Adjacent Areas —

Background and Objectives

It is rather only recently that the familiar landscape of farm village has been recognized as �gthe place to nurture the growth of a rich variety of living creatures�h and its conservation has become a focus of public concern. The natural environment of a farm village is often called a “secondary environment” ; in Japan it has been strongly influenced by human activities because it has been formed and maintained by over 2,000 years of rice growing and other types of agriculture. Accordingly, there is a need to achieve harmony between conservation of biota and development of agriculture and other human activities. In reality, however, the farm village biodiversity is faced with a number of crises which include: (a) alteration of farmland by housing and other development work, (b) changes in the agricultural production process such as the increased use of chemical farm materials and crop changeover, (c) accelerating farm abandonment caused by a decrease in agricultural households and the aging population, and (d) invasion by many alien species.

In the face of such circumstances, efforts are being exerted in many parts of the country to implement various measures to improve conservation of farmland, water resources and the environment in general as well as to introduce Good Agricultural Practices (GAP), directed to promoting the sustainable development of agriculture while conserving the natural environment of farm villages. On the international scene also, attempts are being made to objectively evaluate the relationship between agriculture and the environment, focusing in particular on the relationship between agriculture and biodiversity as an evaluation index.

For these reasons, our research is directed toward clarifying the biodiversity in rice paddies and adjacent areas which form the core of the agricultural environment in our country, and to proposing agricultural activities that contribute to the conservation and management of biodiversity. But �grice paddies�h is a broad term that includes: large-scale paddy fields in plain lowlands, small paddy fields in ravines, and terraced paddies on the slopes in mountainous regions. Likewise, there are big differences among the kinds of plants, insects, fish, amphibians and birds that live in the rice paddies. We therefore focus mainly on plants, insects and birds and aim to analyze the landscape structure of the rice paddy and its adjacent green space in relation to the biota, with the view to contributing to the conservation of biotic community and its diversity in the agricultural ecosystem.

Various paddy landscapes

Expected Outcomes

The long-term ecological impact of herbicides upon endangered plant species living in rice paddy ecosystem will be investigated. Changes in the number of dragonflies in relation to changes in the environment and nearby land use of reservoirs will be predicted. Indexes will be developed on the configuration of rice paddies and adjacent green land (landscape structure), capitalizing on the Rural Landscape Information System (RuLIS) that has been developed by NIEAS. And, methods will be developed by using such indexes to predict and conserve biodiversity. In this way, we will be able to provide information on the types of agricultural landscape structures and land use that are amenable to natural life forms, to propose measures to manage the rice paddy ecosystem directed toward conservation of the biota, and to evaluate and disseminate information on the role of the rice paddy ecosystem in nurturing the diversity of birds and aquatic life.

Green land near rice paddy

Relevant Outcomes to Date

We have successfully developed the frame of the Rural Landscape Information System (RuLIS) that objectively categorizes the agricultural ecosystems all over Japan. We have selected certain monitoring districts out of representative paddy field ecosystems in the Tone River basin and are collecting data on the vegetation of paddies that have been set aside and abandoned, and on avian life and alterations in landscape structure. The prepared database has been used to turn the landscape structure into an indicator to predict changes in habitat, focusing on the “boundary regions (where green lands of different vegetation meet).”  Furthermore, the species composition of dragonflies has been investigated in relation to the environment and use of nearby land, and Copera annulata has been identified as an indicator of dragonfly biota at the reservoirs, to help investigate and analyze the habitat. Also, we took up the use of paddy rice herbicides as a change in the mode of agricultural production, and have revealed that Natant salvinia (Salvinia natans (L.) All.), a floating fern, is highly susceptible to sulfonylurea herbicides.