Investigation into the cause of degradation of biodiversity in rice paddy by diverse fields researchers : the crisis of common species declines

对日本稻田生物多样性下降原因的调查尚不清楚。在以往的调查中，提出了几种关于稻田常见物种衰退原因的假说。本研究以稻田生态系统中常见的物种为研究对象，通过流行病学调查和实验研究，对上述假说进行了验证。对稻田各类群分布区的田间调查结果表明，一些常见种的种群在各研究者的田间已出现下降趋势。此外，物种对干扰因子的反应也因生物类群和生理特性的不同而不同。特别是在使用杀虫剂化学品的特定地区，几种水生昆虫的数量显著下降，如常见的红龙蝇、Sympetrum frequens和其他鞘翅目昆虫。

Investigation into the cause of biodiversity decline has not been well known in rice paddy fields of Japan. Several hypotheses concerning decline causes of common species in rice fields have been nominated from previous examinations. In this research project, these hypotheses were examined for common species in rice fields ecosystem through epidemiological examinations and experimental ones. In results from fields examinations of each taxa distributions in rice fields, some common species populations have been already declined recently in each researchers fields. Additionally, species response to disturbance factors were diverse depending on biological taxa and physiological trait of species. Several species of aquatic insects, especially, remarkably declined in a particular region where had been used an insecticide chemical such as a common red dragon fly, Sympetrum frequens and other Coleoptheran insects.