In 2009, the invasion of L. grandiflora subsp. hexapetala was precisely confirmed in Akanoi Bay, located southeast of Lake Biwa, for the first time (Hieda et al., 2020). At the end of 2009, when initial confirmation was made, the size of the plant’s growth area was 142 m2. However, no countermeasures were implemented at that time, and the area was expanded to 18,292 m2 at the end of 2012.
This study clarifies the government viewpoints and politicians’ interest in L. grandiflora in Shiga Prefectural Assembly and city councils by quantitative data analysis method about L. grandiflora in Akanoi Bay.
As a result, among in Shiga Prefectural Assembly and councils of ten cities along the shore, the Moriyama City Council first mentioned L. grandiflora in 2012. the Shiga Prefecture Council often demanded measures and budgets from the Ministry of the Environment, just as the Moriyama City Council demanded them from the Ministry and Shiga Prefecture. This study also revealed that the congresses of Shiga Prefecture and Moriyama City often explained or suggested the cooperation of citizens and NPOs.
*Hieda S., Y. Kaneko, M. Nakagawa and N. Noma (2020) —Ludwigia grandiflora (Michx.) Greuter & Burdet subsp. hexapetala (Hook. & Arn.) G. L. Nesom & Kartesz, an invasive aquatic plant in Lake Biwa, the largest lake in Japan. The Journal of Phytogeography and Taxonomy, No.68(2), 160～161. (in Japanese)