In the symposium the panelists pointed out there are roughly two causes that brought the increase in numbers. One is expanding urban development. It can affect the habitat of many insects and spiders that make flat (former) agricultural areas their home. Many rice paddies and veggie fields are gone to be warehouses, logistics centers, shopping malls etc. for these 20 years in Kanagawa. The bugs for rural landscape were vanquished. Quiet anger from bug nerds ... Another reason is deer. Especially those insects and spiders dwelling deep mountains of Tanzawa are extinguishing. Voracious deer eat up the plants on the ground and rob housing (of grass and leaves), maternity hospitals (of vegetations that serve as holders of eggs), and meals (for vegetarian bugs). The veterans of bugs census lamented when they did research for 2006 version, the ridge way of Tanzawa around Mt. Hiru (ASL 1673m) 蛭ヶ岳 and Mt. Tanzawa 丹沢山 (ASL 1567m) was covered by Japanese beech and the other trees that loved ASL 1600m of rainy temperate climate. From the road, glimpsing Mt. Fuji to the west was possible only from limited number of points where the tree covers were open. In 2026, no more. Almost anywhere on the ridge of Tanzawa, Mt. Fuji shows off her majestic beauty without obstacles. The place does not have trees, or abundant greenery anymore due to the appetite of deer. Poor bugs have lost their place. Many are dying out.
| I
think it is Phraortes elongatus as its antennae are as long as the half of its body. They are in the watch list for 2026 RL of Kanagawa. |
Deer themselves have a checked life. Until the 1950s, deer was a good protein for starving forest people in Kanagawa. They reduced their numbers to 300 or so in 1947. The authority made hunting female deer illegal. (Guys were spared from it until 1955.) Scientific reason of the policy was unclear and so very arbitrary birth control resulted in population explosion of deer. Their number reached its max, between 5000-13000 by estimate, in 2006. They ate forest. During the1980s, the collapse of vegetation and hence ecosystem became obvious all over Tanzawa. Soil erosion began to show signs of possible catastrophic debris flow to the downstream. In 1997, Prefectural Government started constructing deer fences here and there in mountains. In addition, from 2003 hunting deer by pros and volunteers became main coping strategy (; my post for July 14, 2017). Currently, the estimated deer population is between 1800 to 11000. Within the fences, the vegetation has returned. Is it harasho? It is promising for plants, but for bugs, it seems to me, it is not.
| A
scene in Tanazawa now. Forest floor is only with plants deer do not eat. |
Come to think of it, vegetables can wait until the condition is right in the form of dormant seeds underground. But animals will die out when their habitat collapses. During the 1980s, before Red List making started, probably many bugs were already starved to death. Those survived still faced problems. One of the researchers at the symposium said, “True, within deer fences many vegetables returned. But they are patchworks. Take bees. They need continuous flowers during their entire life. The flowering plants within deer fences often lack variety. They flower all at once. The forests have gap periods in terms of flowers. The seasons sans flowers are for starvation of bees. With such precarious condition, insects cannot return to Kanagawa even if they might have survived in more rural prefectures such as neighboring Shizuoka or Yamanashi.” Hmmmmmmmmmmmm.
| No flower. |
That’s would be a typical example of “lost biodiversity.” I hope it is not a forever thing, but the presenters for the symposium were all gloomy. One of them said “People devised their business model of tourism using the nature of Kanagawa. They innocently said Tanzawa, Hakone, and beaches of Kanagawa are so natural and attractive enough to be monetized. Heck. Do they think they know the meaning of Nature?” Well … At least for now, the best option we could choose would be to watch the changing situation and to raise our voice to stop destruction when it may occur. The organizer of the symposium concluded, “So we decided to have this occasion and make the event public. Please hold critical eyes over the habitat for bugs life and take action when your beloved beetles look in trouble. We need many eyes and voices. Citizen science could save the life of small creatures.”
If you find environmental issues in Kanagawa Prefecture, please make a contact with
Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター
657 Nanasawa, Atsugi City, 243-0121
〒243-0121 厚木市七沢657
Phone: 046-248-0323
You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/
〒243-0121 厚木市七沢657
Phone: 046-248-0323
You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/









