As the Ogasawara Islands are oceanic islands that have never been connected to any continental landmass, unique ecosystems have formed over the course of millennia consisting of unique flora and fauna, which are extremely vulnerable to non-native species. Many non-native species have already been confirmed as having invaded the islands. These non-native species can overrun the habitat of native species, cause disruption at the genetic level, or cause feeding damage on native plants and animals. (Ref. 1)

In particular, under the stipulations of the Act on the Prevention of Adverse Ecological Impacts Caused by Designated Invasive Alien Species, any species that could impose damage are designated as invasive alien species, and their raising, growing, storing, carrying, selling, transfer and importing are in principle prohibited. The main designated invasive alien species that can be found on the Ogasawara Islands include the green anole (Anolis carolinensis; insect predation), cane toads (Bufo marinus; insect predation); predatory flatworm (Platydemus manokwari; predation on native land snails); and rosy wolfsnail (Euglandia rosea; predation on native land snails). (Ref. 1, 2)

 

Ref. 1: Government of Japan, Nomination of the Ogasawara Islands for Inscription on the World Heritage List, 2010, pp. 136-143

Ref. 2: Ministry of Environment website: Measures to tackle invasive species in Japan. 
https://www.env.go.jp/nature/intro/index.html