As I haven’t experienced the condition of the forest 100 years ago in Tanzawa 丹沢, I cannot say in definite the scree-covered forest floor is due to the crash of Philippines Plate and Eurasian/North American Plates, or because of soil erosion brought by the more recent deer problems. One thing for sure. Forest volunteers are in action for forest management, and feel the absolute power of the nature no matter what. Yeah, humans can annihilate the eco-system by dropping an atomic bomb, or even massive deforestation will cause serious problems. We volunteers are not interested in such things. Ours is thinning, mowing, pruning, in a tiny scale compared with the size of Fossa Magna. What we are doing is like “Hello forest, do you mind us helping you to welcome lots of living creatures, humans included?” We know even after a deep-seated slope failure, the vegetation will come back in mountains. Forests are resilient ... Or, are they? In Kanagawa Prefecture, there is another kind of forests. They are Seaside Protection Forests.
Shonan Seaside Protection Forest 湘南海岸砂防林 on both side of the Route 134 |
The seaside road, National Route 134 running the opposite shore of Enoshima Island 江の島 (my post on June 30, 2017), was a part of Tokaido 東海道, the most important artillery route connecting Tokyo and Kyoto. (Due to heavy traffic, the 21st Century Tokaido, aka Route 1, uses only partially the ancient parts, and the majority is expressways. Auxiliary national roads running in parallel to Route 1, such as Route 134, were often the former Tokaido.) Historically, during the Tokugawa Shogunate Period 江戸時代, the entire Tokaido was provided with the facilities, such as frequent road maintenance services and post-towns. The route along the coast was pine tree-lined in order to control the tidal erosion and to provide resting places for travelers. The Route 134 joins with Route #1 in the Oiso Town 大磯 where there are the remnants of such system. Having said that, despite of frequent road maintenances, the coastal road, especially between Enoshima and Oiso, has a serious problem even today of salt damage and accereation of sand from the Pacific Ocean. Typhoons and seasonal strong south-west winds between October and April could cover the road with sand, or destroy the entire structure. Do you know the construction work at Seisho Bypass 西湘バイパス in Oiso Town, due to the high-tide damage by a typhoon in October 2017, could continue beyond 2020? Moreover, beach front is always popular for housing and tourism, which makes the Shonan Beach 湘南海岸 a series of big cities, such as Kamakura 鎌倉, Fujisawa 藤沢, Chigasaki 茅ヶ崎, Hiratsuka 平塚, … People demands their laundry salt-free even their condo is within 10 minutes’ walk from the Ocean. Thus, both national and prefectural governments keep on tending the seaside route with providing the measure, i.e. planting the vegetation.
Construction work is continuing for Seisho Bypass 西湘バイパス |
The forest along the beach |
The
current Seaside Protection Forest of Shonan Beach 湘南海岸砂防林 was
first afforested by modern methodology in 1920. Since then, there were the Great Kanto Earthquake with massive tsunamis, World War II when the Japanese
military deforested pine trees and made Chigasaki Beach a maneuvering ground,
and several big typhoons. Whatever. People have kept on planting. Academics
from University of Tokyo, and Yokohama National University chose the flora that
could survive on sand. Groynes, sand fence of many kinds, windbreak nets, etc.
have been built. At the beginning it was only Japanese black pines and bamboo fences, but for these 100 years, Japanese
brains for botany and civil engineering introduced more diversified
afforestation with Euonymus japonicas,
Japanese cheesewood, and many other
plants protected by permanent structure of wire nets as windbreaker. Now, the
Seaside Protection Forest is 11.4km long for 85.2ha. Its average width is 80m
where more than 15 kinds of plants are intentionally planted by humans.
Afforested
forest of Japanese black pines along Sodegahama Beach 袖ヶ浜, Hiratsuka 平塚 |
Japanese cheesewood near Nijigahama Beach 虹ケ浜, Hiratsuka 平塚 |
In
addition to the above 3 kinds of trees,
carefully chosen species were located along the beach. The list includes Carex kobomugi (ha ha, invasive plants
for the USA), Beach morning, Autumn
olive, Quercus phillyraeoides, Castanopsis sieboldii, Ilex integra, Machilus
thunbergii, Daphniphyllum teijsmannii, Japanese cinnamon, Chinese bayberry,
Japanese camellia, Dentropanax trifidus, Ligustrum japonicum, and Phaphiolepis
umbellata. The way how they are planted is also controlled based on
engineering. First, the grasses such as Carex
kobomugi and Beach morning, are
planted nearer to the shore to reduce the effect of acceration. Next, shrubby
areas are created with Euonymus japonicas,
Phaphiolepis umbellata and others.
Together with the wind-breaking net behind the shrub, the structure acts as the
frontline to protect houses from the shifting sand. Beyond the net is the
forest of higher trees, including black pines, of at least 10m high. In the
middle of the forest runs the Route 134, almost nestled in the forest. Moreover,
planting is just the beginning.
I
think they are dried Carex pumila, in Southern Beach, Chigasaki 茅ヶ崎. (Could you figure out Eboshi-iwa 烏帽子岩 over there?) It seems they were just surviving, but actually acted as a strong buffer for erosion. |
The structure of windbreaker is like this. |
Some
old bamboo nets are remaining. According to Mr. Hiramoto of Kanagawa Prefecture, they think “It’s better leaving them as such to have as many fences as possible.” |
Come
to think of it, this photo may say something amazing about humans and the Ocean … |
The
next level is for shrubs like Euonymus
japonicas. They are all slanted to the leeward due to continuously strong sea breeze. |
Next,
people mow and cut the vines to make supposed-to-be tall trees to grow high
enough for a better barrier. Also, as the entire Seaside Protection Forest runs
along the busy (and fashionable) Route 134 and the residential area, tidying up
the outer rim of the forest is the must to prevent the area from forest fires
and “aesthetically problematic features.” Black pines are vulnerable to Monochamus alternatus (or pine wilt
nematode which the beetle carries). Annual spraying of insecticide is the absolute
minimum. Regular cleaning of the forest with fresh water is necessary to wash
off the salt from the leaves. When a dry spell attacks, people irrigate the
forest of 85 ha. Even with such efforts, die-outs and typhoon damages are not
rare so that continuous supply of seedlings is important for replanting.
Prefectural and contracted nurseries for the above 17 and more species are deployed
within the prefecture. The researchers in Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター are busy creating more resilient black pines
against salt, sand, wind, and pests … Supported by such painstaking efforts,
the seaside afforestation can protect from salt and sand damage both several
meters’ wide of beach spreading windward, and 2-3 hundred meters inland to the
direction of leeward. Amazingly, these days some other kinds of broadleaved
trees have naturally started to invade into the “80m-wide.” Together with such wild
comers the artificially created forests guard the human settlement in Shonan 湘南.
Natural
Environment Conservation Center has a nursery of new-breed of pines in Tanzawa. |
When we
stroll along the Shonan Beach, the forest on the leeward looks “natural.” But
the reality is something of human creation. Yeah, after 100 years of struggle,
we can now find some “natural invaders” in the forest, including vines, but its
conditions are very different from the afforested but “natural” coniferous
forests of Tanzawa. One September weekend, I had a chance to volunteer vine
cutting at one of those forest blocks in Chigasaki City. Mr. Hiramoto for the
Prefecture told us the engineers added black soil and fertilizer before
planting to the sand some 50 years ago. Now the pines are taller than 20m.
Good, good … but I found the ground inside the forest was sandy nonetheless,
and annual spraying inevitably limits the biodiversity with a smaller range of
vegetation. I had a conflicting feeling of cutting Paederia scandens and Pueraria
montana var. lobata … Oh they were so resilient that can start to grow on yet
very sandy soil. But if we allow them to form mantle vegetation by choking off
the afforested trees, relentless winds from the Ocean can quickly cover them
with lots of sand and salt. They will be killed off soon. The point of forest
management in this case is, just let the planted trees to grow, and keep the
forest floor modestly populated with the plants that do not hamper the growth
of human-introduced plants. Er, well …
Pueraria montana var. lobata is covering the artificially planted vegetation at this part of the Protection Forest. |
The
outer rim of the forest shows lots of invading Vitis coignetiae and Farfugium japonicum wrapping the afforested Euonymus japonicas. |
From
outside, the Protection Forest looks having a rich forest floor … |
But
actually the inside is like this. It’s far from a “jungle.” |
Vines
here. I found they tend to be vigorous at the edge of the Protection Forest. It would be due to enough sunshine … |
Volunteers
exchanged the gossip about the Shonan Seaside Protection Forest. I learned the City
of Hiratsuka and Oiso Town has a problem of homeless housing within the Seaside
Forest. The authorities want to let them out, but especially during winter it’s
a popular refuge … When I first heard the story, I imagined the forest floor of
Tanzawa with vampire leeches … Wrong. Inside of the Seaside Protection Forest
has still a limited biodiversity. It’s like a very artificially created park
where boulevards are intentionally omitted by planting the trees closely. Yeah,
the place would be comfortable to sleep outdoors during winter … It’s a very synthetic,
vulnerable man-made forest. Can it survive without heavy human intervention?
Another gossip among us was about progression of coastlines. The sandy beach in
front of Enoshima Aquarium 江ノ島水族館 was at least more than 20m
wider 20-or-so years ago, some locals say. Beaches in Chigasaki and Hiratsuka
are regularly receiving sands from Sagami Lake 相模湖, some
30km away in a deep mountain, when the Water Authority of the Prefecture
dredges Sagami Dam 相模ダム. The endeavor does not stop the narrowing of
Sodegahama Beach 袖ヶ浜 or Southern Beach. When the authority dredges
the Oiso Fishing Port 大磯漁港, gigantic pipes are passed over the wall to
the neighboring Oiso Beaches. The divers vacuum the bottom of the Port and the
gathered sand is spewed off from the pipe to the Beach for sunbathers to relax …
Concreted estuary of rivers, in order to prevent floods in the coastal cities,
changed the supply route of sands from Tanzawa Mountains via the rivers. People
put groynes off the rivers to control the flow. It did not contribute much against
the encroaching sea …
“Over
there years ago, groyens were built to control the flow of sediments from Sagami River. Now we know the tidal structure was changed in definite, but there is not much effect for stopping beach erosion. Beaches in Hiratsuka these days are shrinking.” |
This
is Sodegahama Beach, Hiratsuka, now. Come to think of it the place looked far wider when I was an elementary school kid … |
I a kind
of understood why the people living along the Shona Beach, next to the
Protection Forest, were so “urbanized” This forest is not the forest of Mother Nature.
Rather, it’s to resist the force of nature from the Pacific Ocean ... extremely
inner-city situation in the guise of “natural forest.” Does human effort win
the contest? I doubt it. Rather, rising sea level could overwhelm Japanese
tradition of coastline afforestation sooner or later. Global warming ... Not
all the forests are resilient, I guess. Though, the planet Earth is almighty.
If you
find a problem in Shonan Seaside Protection Forest, please make a contact with
Fujisawa Civil Engineering Office at Shiomidai 藤沢土木事務所汐見台庁舎
1-7 Shiomidai, Chigasaki, 253-0033 〒253-0033 茅ヶ崎市汐見台1-7
Phone: 0467(58)1473
Fax: 0467-58-4953
The
Office has an exhibition garden to show the vegetation they plant in the
Seaside Protection Forest. The place is open to the public, 24/7. 😄
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