*1.1. Background*

Urbanization is an ongoing and persistent global trend [1]. In 1950, 30% of the global population resided in urban areas. By 2018, this percentage increased to 55% and is expected to increase to 68% by 2050. This evidence has several policy implications because it poses environmental, economic, and social challenges for sustainable future development. The trend towards urbanization is also present in Japan. In 2018, 91.6% of the Japanese population resided in urban areas [1], ranking 17th in the world.

Forest restoration is also a global trend. As stated by Mather in his "forest transition hypotheses", forest areas generally decrease in beginning stages of economic development and, in turn, they increase in later developed stages [2–4]. Following intensive exploitation during World War II, Japanese forests have been restored and have now reached "forest saturation" status—a state where a nation has a sufficient quantity of forests [5].

In general, policy indicators determine the extent to which the policy goals are met and often reflect political or institutional factors that influence the entire process [6]. Given the connection between urbanization and forest restoration, forest policymakers need to consider new types of policy indicators that clarify the links between the subjective feelings of citizens and the condition of the forests. For example, following urbanization, the direct

**Citation:** Takahashi, T.; Uchida, Y.; Ishibashi, H.; Okuda, N. Subjective Well-Being as a Potential Policy Indicator in the Context of Urbanization and Forest Restoration. *Sustainability* **2021**, *13*, 3211. https:// doi.org/10.3390/su13063211

Academic Editors: Marc A. Rosen and Ryo Kohsaka

Received: 14 December 2020 Accepted: 10 March 2021 Published: 15 March 2021

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and material dependence on natural ecosystems has decreased, but the importance of spiritual (nonmaterial) values of natural ecosystems has increased [7].

Historically, policy indicators have tended to focus on the physical and objective conditions of the forest. For example, the Japanese national forest plan approved by the Cabinet office, Government in Japan (2018; Table 1) provided numerical goals for the types of forests and their areas, harvesting volumes, tree-planting areas, construction of forest roads, areas of protected forests, and soil conservation projects [8]. These physical forest characteristics have a significant impact on determining the amount of timber as well as the opportunities for recreation. For example, plantation forests and seminatural forests provide different levels of timber production and recreational opportunities. However, with such objective measures, consequences for the subjective well-being (SWB) of individuals who interact with forests remain unclear. Understanding these more subjective measures may help to address forest management problems commonly faced by policymakers in developed countries. For example, forest owners who lose interest in forest management do not properly manage forests [9,10].


**Table 1.** Structure of National Forest Plan (approved by the Cabinet on 16 October 2018) [8].

At the global level, the Food and Agricultural Organization of the United Nations (FAO) conducts a forest resource assessment every 5 years (Table 2) [11]. Nearly all items used in this series of assessments emphasizes forests' physical features, such as total forest areas and protected forest areas.

**Table 2.** Forest resources assessment (FRA) 2015 analysis data table [11].



**Table 2.** *Cont*.
