Coexistence with the Natural Environment & Local Communities | shutoko

Minuma Tanbo Metropolitan Expressway Biotope

In order to revive the ecosystem of the Minuma Tanbo area, one of the few precious green spaces left in the suburbs of the capital, a biotope (place where various creatures of the area live) extending 1.7km under the overhead expressway with an area of 6.3ha was established with the goal of creating "a new urban highway which co-exists with nature" in the Minuma Tanbo area of the Saitama Shintoshin Route. The biotope is monitored (regularly surveyed) while leveraging nature's self-regeneration capabilities, and the area is under minimum required management to naturally nurture plants and animals including transplanted vegetation. General citizens and students studying the environment are working with us on some of the management work. We work with locals, setting up opportunities such as nature observation meetings where local pre-school students can come in contact with small and friendly animals, with the aim of becoming a treasured community-based biotope.

Image of the map of the Minobu Tanbo biotope

Map of Minuma Tanbo Metropolitan Expressway Biotope

A nature observation outing for kindergarten children

Practical work by university students

In addition, in consideration of the surrounding environment, the bridge girders of the highway are painted in dark green, resembling the sloped forest of evergreen trees in the background, and as smooth as possible to fit with the landscape of Minuma Tanbo. Furthermore, we have installed "low position lighting" so as not to affect the animals with the light leaking from the elevated bridges of the Metropolitan Expressway at night. This was also done so that the animals do not confuse night with daytime. This lighting apparatus is put in a box and installed on the bridge railing at both sides of the road (about 1m above the road surface), designed to illuminate only the road surface from the back of the car. In addition, in order to prevent rain water fallen onto the surface of the highway during heavy rain from directly flowing into the nearby Shiba River, we built a balancing reservoir similar to a big tank in the ground of the biotope, partially supplementing the retarding function of Minuma Tanbo.

Image of the painted bridge girder of the highway to harmonize with the landscape

Ohashi "Green" Junction

The Ohashi Junction connecting Route 3 Shibuya Line and the Central Circular Route (Yamate Tunnel) is also called "Ohashi "Green" Junction" because it enabled the creation of environmentally friendly roads and towns. Four organizations i.e. the redevelopment project (Tokyo), the park maintenance project (Meguro-ku), the road projects (Metropolitan Expressway Company), and the locals of the area worked in unison to create the Ohashi "town".

"Three greens"

Ohashi "Green" Junction is an active measure against global warming and heat islands with its three greens, namely the "green for nature regeneration", the "green for park", and the "green for townscape" that contribute to biodiversity.

Green for nature regeneration

The naturally restored green area "Ohashi village forest" built on the roof of the Ohashi ventilation station located inside the Ohashi junction was modeled on the original scenery around the Meguro River. Monitoring after completion confirmed the breeding of killifish, etc. brought from local ponds, insects, aquatic organisms, and the arrival of many birds.

Green for park

"Meguro Sky Garden" on the rooftop of Ohashi Junction is a huge loop shaped park run by the Meguro ward with a length of about 400m, a height of 7 to 35m, and an area of about 7,000m². “Opus Yume Hiroba", a multipurpose area of about 3,000m² was built on the inner side of the junction loop.

Green for townscape

We are applying a green cover along the walls of the Ohashi Junction starting at ground level by using the creeping fig (a creeper that climbs directly upwards), an evergreen ivy, taking into account its fit with the surrounding environment. The creeping fig grows slowly at about 30 to 50cm per year, but a stately green cover forms on the Colosseum-like walls as time goes on.

Image of the greening surface of the Ohashi junction

Ohashi village forest

The naturally restored green area "Ohashi village forest" was built on the roof of the Ohashi ventilation station located inside the Ohashi junction. Recalling the time when people and nature were deeply connected, the sloped forests, grasslands, the murmur of streams, etc. were reproduced. The special shape of the roof of the ventilation room (consisting of a slope inclined by 28% and an upper and lower flat section) simulated a river terrace on the Meguro River in the early Showa era. Sloped forests, grasslands, springs, streams, ponds, and paddy fields were created here. We restored the planting landscape based on the original landscape around the Meguro River, and developed it with the goal of creating an environment that will serve as a habitat for various living creatures. In fact, we confirmed the arrival and inhabitation of the creatures in the table below from August to October after the work. "Ohashi village forest" connects greenery around Yoyogi Park and other establishments, and is expected to function as one of the new bases of the Ecological Network centered on the Meguro River. In addition, "Ohashi village forest" holds rice farming events for elementary school students in the area.

Landscape of the Meguro River

Birds 4 types

Blue-rock thrush/Black-backed wagtail/Brown-eared bulbul/Japanese white-eye
Insects (land-dwelling) 61 types

Common skimmer/Autumn darter/Loxoblemmus campestris/Velarifictorus micado/Tetrigidae/Oxya yezoensis/Large brown cicada/Seven-spotted lady beetle/Drone fly/The straight swift/Asian swallowtail/etc.
Insects (aquatic) 8 types

Gray diving beetle/Backswimmers/One type of water strider/Ischnura asiatica (dragonfly nymph)/Anax parthenope (dragonfly nymph)/Orthetrum albistylum speciosum (dragonfly nymph)/Scarlet skimmer (dragonfly nymph)/Sigara substriata

Image of the network of living creatures

Rice planting

Nature observation outing

Harvesting rice

Threshing

Registered in EDO-MIDORI Registration Green Space

On August 21, 2019, Ohashi Village Forest was registered in "EDO-MIDORI Registration Green Space (*)" which is the native species planting registration system of Tokyo Metropolitan Government.

Ohashi Village Forest was highly evaluated for reasons as follows.

Plantation only focusing on native species
Preservation of natural condition without excessive pruning
Management methods without pesticides

(*) "EDO-MIDORI Registration Green Space" is a system that Tokyo Metropolitan Government registers and announces green spaces, actively planting native species and working on biodiversity conservation.

JHEP certification "AAA" (highest rank) acquired

"Ohashi village forest" was modeled on the original scenery around the Meguro River, restoring quality natural areas, by methods such as restricting the type of seedlings to native species modeled on the original nature of the area. From the start, the area was thoroughly maintained, not allowing excessive pruning to encourage naturally shaped trees and grassland growth, and alien plant species were exterminated in order to cultivate native species.
"Ohashi village forest" was praised for these improvement and maintenance efforts, obtaining the highest ranked "AAA" among JHEP certifications.

*JHEP certification (Japan Habitat Evaluation and Certification Program) is a system that quantitatively evaluates the contribution to and impact on biodiversity from companies' initiatives, based on comparisons made before and after the projects. The Ecosystem Conservation Society-Japan evaluates and certifies the initiatives in Japan. The Japanese version of HEP, developed by the US Department of the Interior in the 1970s and 1980s as a method to quantitatively evaluate the environment.

Image of the JHEP certification ceremony

03. Active Implementation of Environmental Technology

04. Coexistence with the Natural Environment & Local Communities