“Shikinaisha” is the standard term used to refer to jinja that are listed in the “List of Kami” in the early tenth-century Engishiki. These jinja are important because the text records 2861 jinja across the whole of Japan at that time (so not including Okinawa or Hokkaido). There is, in general, a higher density of jinja nearer the old capitals in Nara and Kyoto, but there are remoter areas with surprisingly high numbers. Thus, these are demonstrably ancient jinja that, as a whole, are probably somewhat representative of Shinto practice over a thousand years ago.
The sacred forests article in the April 11th issue of Jinja Shinpō was by someone who has, so far, visited just under 4,700 of them.
Particularly alert readers may have noticed a discrepancy in these numbers. This arises because there are, in some cases, multiple candidates for being the jinja mentioned in the Engishiki. The text gives the name of the kami or jinja, and its location by province and county. However, counties are fairly large, the names of jinja can change, and jinja themselves can be moved, for a number of reasons. Some of the identifications are completely secure (Izumo Ōyashiro or Kashima Jingū, for example), but there are many cases that are less clear.
As the author notes, the shikinaisha were founded in a wide range of locations, in response to different religious practices. Some were in or on the edge of towns, some were at important road or river junctions, some marked the boundary between the territory of people and the territory of the kami, and some were deep in sacred mountains. The ones that were deep in the mountains are the ones that are most likely to be difficult to identify. The author had frequently needed guidance from people connected to a jinja, and on some occasions he found the jinja, but was not able to get close to it because of thick bamboo. His more spectacular misadventures include only surviving a falling tree because, by chance, he was wearing a helmet that day, and getting caught in a deer trap. (Around this point, I decided that I wasn’t that interested in visiting all of these jinja.)
He makes several observations based on his experiences. First, he emphasises the importance of the original locations of the jinja. He feels that the particular locations where the jinja were first established have the most sacred atmosphere. His second point is that, even given the importance of the original location, there is no way to avoid moving some of the kami to more accessible locations if matsuri are to be continued. In that case, he recommends preserving the original site as a sacred forest, with a stone monument recording the fact that the jinja was originally there. He encourages creating a full record of these jinja, including the ones that are not currently religious corporations.
His third point is that the traditions of Shinto could be drawn on to make the jinja easier to maintain. He observes that some of the shikinaisha have no buildings at all, just a location for matsuri, while others have no main sanctuary, just a prayer hall facing a sacred stone. At some, the main sanctuary is a small stone structure, and matsuri are performed in front of it. Many of these forms are a lot easier to maintain up in the mountains than a “standard” jinja complex. If there is nothing more than a space for matsuri, clearing plants away every time you go to perform the matsuri is sufficient, and stones will survive a long time with minimal maintenance.
I think these are excellent points. The Shinto world does need to start thinking outside its conventional structures if it wants to preserve all of its ancient sacred locations.