Yakushima is a Japanese island whose cedars grow so slowly that some have been standing for thousands of years. It is a granite dome off the southern tip of Kyushu, in the path of the warm Kuroshio current, and it makes its own weather. Air loaded with moisture off that sea hits a wall of peaks nearly two kilometres high, and empties itself going up. The mountains take several metres of rain a year. On thin granite soil the cedars add wood at a crawl and pack their rings with resin, so the timber barely rots. A tree that would be old at five hundred years on the mainland is ordinary here. From the mountain road you can watch it happen: ridge behind ridge of green interior, cloud sliding down over the tops.
The walk to the greatest of those trees starts on a railway. The rails once carried its felled relatives down to the coast. The trail follows them, then turns off and takes you up a hard climb, eight to ten hours there and back. Halfway along is what is left of a cedar cut around 1586 for a temple Hideyoshi was raising in Kyoto. The stump is 13.8 metres around and hollow enough for you to walk into, with a spring welling through the floor and the opening overhead framing a heart of sky. Shiratani Unsuikyo is the ravine Miyazaki's team came to study: granite boulders furred over in moss, trunks leaning across the stream, at its most extreme if you arrive within an hour of rain. An old saying counted the island in three equal parts: twenty thousand people, twenty thousand monkeys, twenty thousand deer. The people are down to about twelve thousand. The macaques and the small Yaku deer, found nowhere else, still sit on the forest roads. On early-summer nights loggerheads haul up the dark sand at Inakahama, the biggest nesting beach in the North Pacific. And the long walk ends at a deck before a trunk 16.4 metres around, with a couple of thousand years behind it, on ground its relatives were carried off.