Chinju no Mori (Sacred Shrine Forest) (鎮守の森)
The forest enshrines Kannabi (also called Kamunabi), a kami (spirit or god) of Koshinto (literally 'old Shinto,' as practiced prior to the introduction of Confucianism and Buddhism), and so is also known as Kamishiro (literally 'ancient times').
Since every shrine used to be surrounded by a Chinju no Mori, it is often written with a character meaning 'a god's forest,' as opposed to the normal character for forest. There are also examples of the characters for 'shrine' (usually pronounced 'jinja') being read as 'mori' (forest), which reflects that Shrine Shinto derives from Koshinto.
If you look at a shrine from a distance, there is usually a thick forest with a torii gate at one end. From the torii, the Sando leads into the forest until reaching the shrine precincts and Honden (main shrine), behind which is the main body of the forest, meaning worshippers face into the heart of the forest. This clearly shows that 'Yashiro' (shrines) did not come first, but were built in forests that were already worshiped. In cases where there is a long-protected forest near the coast, known as an Uotsuki Rin (literally 'fish-attracting woods'), there usually is a shrine.
The Shintai (an object in which a kami is believed to reside) of present-day Shrine Shinto is the 'Yashiro,' including the Honden and Haiden (hall of worship), marked by a shimenawa (sacred rice-straw rope), and the Chinju no Mori is understood to be the forest surrounding it.
However, Koshinto, which is the origin of Shrine Shinto, worships at Himorogi (a temporarily erected sacred space or "altar") and Iwakura (dwelling place of a kami, usually a large rock), with nature itself, including forests and the land covered by forests, mountains (such as holy Mt. Fuji), gigantic stones, the sea and rivers (distinguished places include reefs and waterfalls), being the sacred object.
Most shrines of Shrine Shinto were originally established in such sacred sites or where there was a Himorogi or Iwakura, which were considered to be the border between Tokoyo (the world of the dead) and Utsushiyo (the actual world) and as such, a sacred tree or rock can be found serving as the Shintai in the precincts of shrines. Just like Koshinto, there are some shrines even today, such as Omiwa-jinja Shrine, which enshrines Mt. Miwa in Nara Prefecture, that regard mountains themselves as the kami's Shintai or Yorishiro (an object capable of attracting kami). Some shrines don't even have a Honden or Haiden, the Shintai being a forest or the hill it stands on; these shrines have passed down Koshinto, an indigenous religion which worships nature and the dead.
According to Akira MIYAWAKI, 'Chinju no Mori' is used as a academic term by the International Association for Vegetation Science.
On the other hand, there are some cases of Chinju no Mori being made for a shrine. Meiji-jingu Shrine is especially famous. Although some species were brought from places such as Taiwan, the policy was to take into account the vegetation (potential natural vegetation) of the area, and the Chinju no Mori was planned to grow as a natural forest.
Chinju no Mori are considered to have been preserved as they were in ancient times. Consequently, the forest is thought to preserve the original vegetation, the so-called potential natural vegetation, of the area. Since the surrounding natural environment is usually destroyed today, Chinju no Mori are often one of the few keys to knowing what the natural state of the area used to be like. In that sense, Chinju no Mori are important for Japanese silviculture, where they are known as Jinjarin (shrine forest) or Shajirin (temple forest) and are often surveyed. In the process, if their value is confirmed, many of them gain protection as natural monuments. The forests attached to Utaki (sacred places) in Okinawa are similar in that sense.
However, it is better not to think that all of the forest is old vegetation. When the surrounding area is developed and the Chinju no Mori is left isolated, the vegetation, which originally covered a wide area is cut back. As a result, the area becomes smaller, which makes it highly likely that some species will disappear. Although some species may continue to grow along side streams, these areas are not included in Chinju no Mori and so large parts of the forest, having existed for centuries, are lost. At the same time, aridification also often occurs. As a result, some parts change and new species move in. For example, it is believed that the camphor tree commonly seen in shrines did not originally grow in forests in southern central Japan. Also, deciduous trees such as the keyaki (a type of elm) and the muku tree are not supposed to commonly grow in the mature forests located to the south of the flatlands in central Honshu (the main island of Japan).
In many cases, this segmented vegetation cannot guarantee enough land to maintain the populations of the animals that live there, and the decline of the animal community is considered to be worse than that of the plant community. Since most plants need a specific animal for pollinating and seed dispersal, such declines in the animal community can affect the vegetation itself in various ways.
The forests are also affected directly by people. Non-wild plants are often planted in the precincts of shrines. When a tree falls, trees such as sugi (Japanese cedars) or cypresses is often planted to fill the space (the technical term is "gap") left behind. It has been reported that the utilization of forest resources in the precincts of shrines has been increasing in recent times. In recent years, maintenance such as weeding and raking of fallen leaves has been carried out in some forests but, when done in a natural forest as opposed to forests maintained for wood fuel or planted forests, this promotes degradation. In other cases, forests are sometimes cut down around their circumference, or the edges are trimmed to make way for road expansion. In such cases, the floor of forests that have lost their mantle or fringe vegetation tends to dry out, making them prone to degradation. What is more, there is increasing use of repair methods, such as spraying concrete, which are simple but leave no chance for natural recovery.
Nevertheless, different from so-called Satoyama (undeveloped woodland near populated areas), Chinju no Mori retain a certain character, familiar to most people even while being treated differently from forests that are maintained for human use.
Today, since belief in the kami of Shinto has become more abstract, reverence for the dense Chinju no Mori has faded, and the shrine forest, for believers such as ujiko (shrine parishioners), is often considered to be dispensable. Therefore, they are readily reduced in size when improving roads, and are sometimes reduced to make way for public facilities such as nursery schools. Furthermore, in big cities, some forests have been completely lost. There are shrines consisting of only a torii gate and a Honden, with the meaning of the shrine as an addition to the original nature worship already lost.
In the past, before the Meiji period, there used to be shrines of varying size in each settlement, each surrounded by a Chinju no Mori. Their number was reduced significantly following what is known as the Shrine Merger Order. This resulted in many shrines being abolished, and at the same time, their Chinju no Mori being cut down. Kumagusu MINAKATA opposed the shrine mergers, fearing that this deforestation would cause large-scale destruction of the natural environment.
There is a theory that the objective of the mergers was actually the acquisition of rights to the lumber and its by-products (such as camphor). Shrines located to the south of the central Honshu in particular had lots of big trees, including camphor and tabu (machilus thunbergii) trees, which were said to fetch large sums of money.
On a smaller scale, sacred trees in shrines often had large samurai orchids (neofinetia falcata) or Sekkoku orchids (dendrobium moniliforme) growing on them, but they are hardly seen these days due to the influence of the wildflower boom. There seems to have been a similar case in the past, when Kumagusu MINAKATA found large, imposing epiphytic orchids at a shrine in Wakayama Prefecture and delightedly told the Shinto priest.
However, the priest gave it a lot of publicity, angering Kumagusu, who wrote, 'it is terrible to publicize such an exceptional thing like that. It will end up stolen.'