| MIURA PENINSULA A Seaside Nature Treasurebox |
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| Japan is blessed with abundant sea life. Among the coastal ecosystems of
the temperate zones of the world, Japan's is one of the richest (maybe
the richest). There are mainly two requisites for rich coastal ecosystems: geographycal
variation and the ecological abundance on land. Japan's coastal regions
meet both. Its complex coastal lines provide a variety of niches to numerous
creatures. The land receives twice as much rain as the world' average,
and rivers and streams in every corner of the land carry nutrition into
the sea. Seashores around Tokyo are also such ecologically rich environment. Sadly, few people are aware of the blessings. We can not blame them since seemingly lifeless Tokyo Bay repels their attention. But take an excursion just a little further, and shores of Miura Peninsula awaits you to reveal just how rich life of the seashore can be. These shores are worth much more attention than we have been aware. |
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| A Treasurebox For Nature Enthusiasts Because the condition of water on Tokyo Bay side is not really good, we focus our attention to shores on Sagami Bay (west coast of the peninsula). The west coast shows a variety of shore types: rocky shores, sand beaches, inlets, and tidal flats, so you can enjoy almost all varieties of seashore ecosystems. In addition, since the seabeds near the shores are rather shallow, and Sagami Bay protects them from rough waves of the mighty Pacific, waves on these shores are kept gentle. Considering all these and the easy approach from Tokyo, Miura Peninsula seashores make ideal seaside nature play spots. Northern part of the peninsula provides good sand beaches, whereas southern part are mostly consist of rocky shores with some Rias coasts. But the climax of the peninsula's nature spots concentrate in the southern tip, along the rocky shores. |
| One such spot is Arasaki. This coast is characterized by rough rocky terrains,
which makes it a scenic spot like those found in Hiroshige's and Hokusai's
ukiyoe prints. But the real wonder of this seashore will not be revealed
till you take a glance under your feet. Great varieties of sea creatures
await your attention. People in general do not seem to be interested in rocky shores, since the topography is often so rough that swimming (and even sunbathing) is hard. But if you are a nature enthusiast, a rochky shore is your much sought-after treasurebox. Hundreds of small shells are makig their slow moves. The quick moving shells are catually not shells but hermit crabs. In addition, do not be surprised when you notice that the kelp that makes the dense thicket just under your feet is the one you had on the traditonal Japanese breakfast table this mornig (hijiki). There are other hundreds of tiny creatures you have never seen, crawling in narrow rock ditches (or holding fast to the rock). |
| A Little Lecture On The Rocky Shore Ecology Seashores are influenced strongly, hence determined to a great extent, by tide. Generally, rocky shores are divided into three zones: The zone above high tide is the supratidal zone, (also known as the spray zone) which is covered by water only during storms. The zone between high tide and low tide is called intertidal zone. The zone below low tide is called subtidal (also infralittoral) zone. The most talked-about among the three is the intertidal, and the reason is clear: this zone is the richest in biodiversity. Typical inhabitants include sea anemones, barnacles, chitons, crabs, limpeds, mussels, sea stars, sea cucmbers, and sea urchins (I hope you know what I am talking about). Tidepools belong to the intertidal, and seem to attract people's attention. But tidepools are not really very rich in diversity because they are often unstable and too harsh for many living creatures. Rather, we need to pay attention to "tideinlets", because they are the very niches where we find most abundance in life forms. |
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Another spot to recomend for nature enthusiasts is Koajiro, in which a small valley of about 1mile long flows down into an inlet (actually, a 2mile long valley of which a half is above water and another half underwater) . There is a tiny stream in the valley, whose mouth into the sea forms a mudflat. No permanent resident (human resident) lives in the valley now, and no concret structure obstructs the ecotone between land and sea. The intact seashore with natural ecotone keeps this place a sanctuary for many living things. |
| Among them, the most well-known is the akategani (no English name: direct translation is red hand crab). This crab used to be found anywhere near coastal regions. But invasion of concrete structures at sea shores, particularly at river mouths, drove them into fewer and fewer places available. Surprisingly, in the entire Kanto area today, Koajiro is perhaps the only place where the crabs are able to make their life as they once used to: i.e. in sufficient number. The adult crabs live in the nearby forest. (they even climb trees). At spawning time, they come down to the shore. So for their survival, they need forest near the sea, and safe routes to the sea to spawn. But such a condition has bocome a rarity in today's Japan. Koajiro keeps such a rare and precious environment. |