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Drastic decline in Japan's butterfly population; other wildlife also feared endangered

The great purple emperor, the national butterfly of Japan, is seen in this photo taken in Nabari, Mie Prefecture, in 2016. (Mainichi/Yasutoshi Tsurumi)
A genji-botaru firefly is seen in this photo provided by the Nature Conservation Society of Japan.
A hare is seen in this photo provided by the Nature Conservation Society of Japan.
A Japanese marten is seen in this photo provided by the Nature Conservation Society of Japan.

TOKYO -- A fixed-point observation of wildlife between fiscal 2005-2017 in woodlands near villages across Japan found that some 40% of common butterfly species have declined in number and are likely endangered, according to a report released by the Environment Ministry and the Nature Conservation Society of Japan (NACS-J) on Nov. 12.

Other wildlife including hares -- initially considered as having a relatively low risk of extinction -- are also plummeting in number. Experts are demanding that immediate efforts need to be taken to preserve the habitat of these animals.

The Ministry of the Environment, which constantly monitors plants and animals at some 1,000 sites in mountainous and coastal areas, compiled the results of research carried out in 192 woodlands. Furthermore, it examined a shift in the population of 87 common butterfly species that were spotted from fiscal 2005-2017, with the help of local residents and NACS-J.

The ministry found that 34 such species, or around 40%, had decreased in population by at least 30% pointing out the possibility that they are now endangered.

In particular, the population of great purple emperor, Japan's national butterfly, the Alpine black swallowtail and four other species are presumed to have drastically declined by over 90%. It was concluded that the numbers of these six species are now equivalent to those classified as "Endangered Class IA" on the ministry's red list of threatened animals at the highest risk of extinction.

According to the ministry, common causes for the shrinking numbers of butterflies likely include deer-induced damage to tree bark and undergrowth, water pollution and the use of agricultural chemicals.

"Another reason might be the neglect of woodlands by humans, causing the area to become dilapidated, diminishing the number of plants necessary for a suitable environment (for butterflies)," said Minoru Ishii, professor emeritus of entomology at the Osaka Prefecture University who is well-acquainted with butterfly ecology. "I believe the reduction in the butterfly population could have an impact on other creatures, like birds," added Ishii.

"The data is really shocking," stated a representative of the Environment Ministry.

Other species believed to have become endangered are hares, which mainly inhabit grasslands, Japanese martens, which inhabit the forest, and two types of fireflies including genji-botaru, and Montane brown frog, which both inhabit waterside areas.

(Japanese original by Kazuhiro Igarashi, Science & Environment News Department)

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