The Critically Endangered dragonfly Libellula angelina, known as the bekko tombo, of central and northern China, Japan, western South Korea, and North Korea, was common before 1970 but has declined dramatically as a result of habitat loss caused by urbanization. In China, natural ponds and wetland parks have facilitated the survival of this species in megacities such as Beijing and Tianjin, but habitat degeneration in some cities appears to be resulting in further decline of the species.
The natural ponds around the Chentai Bridge in Beichen district, Tianjin, one of the historical habitats of the bekko tombo, suffered a severe drought from excessive pumping for irrigation in spring 2020, followed by excessive water supplementation that increased the original water level in autumn 2020. In Tianjin Water Park, another habitat of the bekko tombo, sediment was dredged and reeds mowed, destroying habitat for the species’ nymphs and imagoes, respectively, in 2020. During 15 April–15 May 2021, we surveyed for the bekko tombo in these two habitats on 18 occasions, concentrating on their preferred microhabitats in reeds and open grassland, but failed to find the species. Prior to this, the bekko tombo was commonly seen in these two areas in spring.
The prime habitat for the bekko tombo is unmodified, stable and organic-rich ponds with open water and moderate growth of emergent plants. Urbanization and habitat degradation, accompanied by reclamation, drought, contamination, sediment dredging, mowing of reeds and shrinkage of wetlands, are driving the collapse of the remaining populations of the bekko tombo. Measures are required to maintain the integrity of the species’ habitat by protecting wetlands from urbanization and anthropogenic modification, with a halt to inappropriate dredging and mowing.
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