pureamericanism:

One effect of these policies [preserving domestic peace and minimizing foreign contact] was to preclude a common solution to the problems caused by resource overexploitation: seizing neighboring territory to compensate for what one’s own area no longer provides. The people of Tokugawa Japan, high and low alike, had to make do with what they had and what they could acquire peacefully, and they knew it. These government policies had the additional effects of preventing the introduction from abroad of disequilibrating technology and ideas and of sustaining at home a general faith in the immutable nature of the social order. People simply took it for granted that the essential character of the future was knowable: they could prepare for it, but they must do so with the resources at hand.

From The Green Archipelago: Forestry in Pre-Industrial Japan by Conrad Totman

This is a little questionable - the Tokugawa era was when Hokkaido was really brought into the Japanese fold and developed for farming, a process that involved suppressing native Ainu unrest by force.

There’d been Yamato presence on Hokkaido before (the Yamato are the ethnic group generally thought of as “Japanese”, there are a few other groups indigenous to the islands and scholars outside the particularly nationalist Japanese academy generally agree that the Yamato culture came from the Korean peninsula), but they’d settled the island in the same sense the French settled North America - very lightly, for the purpose of trade with the natives. Hokkaido is the least mountainous of the home islands and thus the most agriculturally productive, with a climate suitable for the cultivation of wheat and barley.