The impacts of systemic pesticides on biodiversity are a major ecological concern. Rapid population declines of Sympetrum species (Odonata: Libellulidae) have been reported in various localities in Japan beginning in the 2000s. Several studies suggested that nursery box use of fipronil in paddy fields to prevent insect feeding on rice seedlings negatively impacts Sympetrum larvae. Although several other Odonata species are suspected to have declined significantly in recent decades, accurate evaluations of their population declines and identification of the causes are difficult due to limited data on population density prior to the declines. In addition, a recent study revealed that herbicide use negatively affects phytophilous species, but positively impacts benthic populations of lentic Odonata by reducing the prevalence of macrophytes. To evaluate the changes in the abundance of Odonata during recent decades, we conducted line transect observation of Odonata populations at one site along the Tafusegawa River in Saga Plain, northern Kyushu, Japan in 2000 and 2015–2016, before and after the use of fipronil in paddy fields in this area. We identified that Sympetrum eroticum eroticum (Selys) (Libellulidae) populations have significantly decreased in recent years. In addition, prevalence of a lotic benthic species, Asiagomphus pryeri (Selys) (Gomphidae), has significantly decreased in this time period. Other lotic benthic species have also declined in this area, suggesting that benthic environments might have degraded in recent years. In contrast to the decrease of the abovementioned species, prevalence of the lentic and benthic species Orthetrum melania melania (Selys) and Rhyothemis fuliginosa Selys (Libellulidae) (Libellulidae) significantly increased. The densities of lentic phytophilous species appear to have decreased, suggesting that reduction of macrophytes in surrounding lentic environments could be involved in these changes.

中文翻译：

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日本九州北部佐贺平原 2000 年和 2015-2016 年间蜻蜓的丰度变化

内吸性农药对生物多样性的影响是一个主要的生态问题。从 2000 年代开始，日本各地报告了 Sympetrum 物种（Odonata：Libellulidae）的种群数量急剧下降。几项研究表明，在稻田中使用氟虫腈以防止昆虫以水稻幼苗为食的育苗箱会对 Sympetrum 幼虫产生负面影响。尽管最近几十年怀疑其他几种蜻蜓物种数量大幅减少，但由于数量减少之前的人口密度数据有限，因此很难对其种群数量下降进行准确评估并确定原因。此外，最近的一项研究表明，使用除草剂会对亲植物物种产生负面影响，但通过减少大型植物的流行，对扁豆的底栖种群产生积极影响。为了评估近几十年来蜻蜓数量的变化，我们于 2000 年和 2015-2016 年在日本九州北部佐贺平原田风川沿岸的一个地点对使用氟虫腈之前和之后的蜻蜓种群进行了线状断面观察在这个地区的稻田里。我们发现 Sympetrum eroticum eroticum (Selys) (Libellulidae) 种群近年来显着减少。此外，在此期间，嗜水底栖物种 Asiagomphus pryeri (Selys) (Gomphidae) 的流行率已显着下降。该地区的其他底栖物种也有所减少，这表明近年来底栖环境可能已经退化。与上述物种的减少相反，懒虫和底栖物种Orthetrum melania melania (Selys) 和Rhyothemis fuliginosa Selys (Libellulidae) (Libellulidae) 的流行率显着增加。植物性植物物种的密度似乎有所降低，这表明周围植物性植物的减少可能与这些变化有关。