4.1. Discussion
In recent years, farmland abandonment has become a serious issue in Japan, which reflects agricultural loss as well as depopulation and an aging society. However, for a better understanding of this issue, the regional characteristics and determinants need to be explored further. This study employed OLS and GWR, which focused on different perspectives, to investigate farmland abandonment. The findings can provide an explicit explanation of the spatial characteristics as well as the determinants of farmland abandonment.
Firstly, spatial patterns of farmland abandonment in Japan were uneven, and different regions shared different extents of farmland abandonment, which strongly corresponded to regional geographical conditions and agricultural development. Compared with the national level and considering their spatial patterns, we divided the seven regions into three categories: low abandonment, moderate abandonment, and high abandonment. Among these, Hokkaido lagged behind the national level and had low abandonment (
Figure 12). Here, farmers overcome harsh geographical conditions, develop agriculture sustainably, and also possess different agricultural development paths and land tenure compared with other regions [
23]. The Tohoku region and Kinki region had moderate abandonment, while the majority of the low-low abandonment agglomerations or cold spots (
Figure 5) and the FLAR were similar to those of the national level. Agriculture in Tohoku is typically well maintained and is famous for the monocropping of rice. In addition, farm households have strong kinship ties and many young generations assist their elder parents in agricultural work [
55]. In GWR, paddy field density and the ratio of non-successor farm household also exhibited a strong correlation associated with FLAR in Tohoku (
Figure 7 and
Figure 9). Northern Kinki has a good farmland condition, while southern Kinki is a mountainous area, and agriculture is experiencing challenges in terms of fruit, vegetable and tea production. On the eastern coast of Tohoku, the FLAR varied greatly from 2010 to 2015 (
Figure 4). Meteorological factors play a key role in coastal areas due to the extreme weather conditions throughout the years, such as monsoon and seasonal currents, which adversely affect agriculture. The Chugoku Shikoku, Kanto, Kyushu and Chubu regions exhibited high abandonment levels, which were obviously higher than the national level (
Figure 12). In these regions, most of the areas had a high FLAR, along with high-high agglomerations or hot spots (
Figure 3 and
Figure 4). Farmland in the Kanto and Chubu regions is constrained, either from the high elevation under the Japanese alps or urbanization in association with out-migration of laborers to metropolises [
40]. In the Chugoku Shikoku region, rural depopulation first occurred in mountain zones, along with serious aging and issues associated with a lack of agricultural successors [
56]. Many plots in coastal areas were previously used for orange production, but from 2010, due to low yields, farmers abandoned their orange fields, which contributed significantly to the increase in the FLAR without any mitigation until now.
Secondly, the combination of global and local regression in interpreting determinants of farmland abandonment in Japan generates a comprehensive understanding. Based on the global regression, geographic variables, such as slope, demonstrated a significantly positive correlation with farmland abandonment, which has already been reported in previous studies [
1,
15,
32,
42]. In Japan, soil condition may also relate to regional abandonment. There are cases farmers transport soils (known as soil dressing or
Kyakudo in Japanese) from the higher mountains to enrich the fertility of their paddy fields. In contrast, expressway and railroad densities did not exhibit a significant correlation. Agricultural production in Japan is highly mechanized in the face of laborer supply shortages, and so farmers are more concerned about the accessibility of agricultural machines than road conditions, which are well maintained in rural Japan. Socio-economic variables, such as successors of farm households and laborers per farm household determine abandonment, which is similar to previous results [
15,
18,
24,
34,
35,
38,
55,
57]. However, the significance of variables such as the arable land ratio of self-sufficient farm households, arable area per household and paddy field density are interesting and unique in a Japanese context. The above conclusions were only drawn from the perspective of global regression. In regard to local regression in GWR, Hokkaido had a low FLAR, and it exhibited an obviously different pattern compared with other regions, which corresponds with Osawa et al., (2016) [
22]. In addition, we found discrepancies in the other six regions, as well as localized output coefficients, which may depend on local geographical or socio-economic circumstances. In particular, the Chugoku Shikoku region had the highest FLAR among the seven regions in Japan, and it shared a significant spatial correlation with many variables in GWR. Non-successor farm households, the arable land ratio of farm household and laborers per household displayed the most significant correlation here. The explanatory ability of other variables varied greatly across regions, and specific theories and reasons behind this need to be discussed further.
Thirdly, as is heavily depopulated especially in rural areas, Japan has an unfavorable socio-economic condition for agriculture, which adversely promotes the increase of abandoned farmland. Generally, farmland abandonment in Japan is due to its subsistence farming. Because of aging and depopulation in Japan, elderly farmers lack sufficient labor and rely on mechanization while young people have lost their passion for agriculture, and thus the conversion of farm households from commercial to self-sufficient was expected. From our result, the arable land ratio of self-sufficient farm households exhibited the most significant positive effect. It seems that there are limited commercial activities for elderly farmers to engage in agriculture or farming, or many of them engage in agriculture for their own living, thereby increasing the likelihood that farmers will abandon their farmland when encountering difficulties. In addition, monocropping of rice also resulted in farmland abandonment, and in particular dry land and fruit gardens contributed the most to abandonment. Japanese agriculture is centered around rice cropping, where rice paddy fields are essential components of agriculture, accounting for 54.3% of the total arable land area [
25]. However, paddy field areas are declining, partially due to policies such as the adjustment of rice production [
58], which have been in place since the 1970s to encourage farmers to switch crops and to diversify the use of agricultural land. Eventually, the adjustment of rice production maintained the price of rice in the face of overproduction [
59]. However, numerous farm households, especially self-sufficient households, were not willing to change their land to other crops, and this policy became ineffective. Our result showed a negative correlation between the paddy field density and FLAR in most regions, which indicated that paddy fields are easy to maintain, and farmers are fond of rice farming. How to change people’s consciousness and diversify the use of farmlands remains a future challenge for the Japanese government. Lastly, agriculture in Japan relies heavily on subsidies [
60]. Besides the adjustment of rice production, a direct payment policy was also issued in 2000 in hilly and mountainous areas to maintain agricultural farmland [
61]. In contrast to the European context, this fund is paid to community-based agricultural unions instead of directly to individual households [
62]. Many areas ill-suited to agriculture depend heavily on these two subsidies; hence, the approaches were not particularly effective at maintaining the farming of good-quality agricultural land. Thus, the situation brought little benefit to agricultural development, and it was not effective in preventing the expansion of abandonment.
Finally, we discuss the limitations of this study and recommendations for future research. One limitation is the limited number of socio-economic variables to evaluate farmland abandonment. In our study, we only considered data that is available from the agricultural census at former municipalities scale. Although census data can correspond to former municipalities spatially in GWR, some important information such as rural–urban migration [
18], labor market [
6] etc. are still missing. Future research can consider different scales and variables relate to these aspects as well. Moreover, the concept of farmland abandonment defined by MAFF only considers short-term abandonment and ignores accumulative abandonment, which is a more stable and concise way to discuss abandonment. Furthermore, there is a significant amount of hidden abandonment (hidden abandonment or semi-abandonment is farmland where agricultural production ceases, but the land is maintained as cultivated farmland. Hidden abandonment is between cultivated and abandoned land, which has a high risk of being abandoned in subsequent years [
63]), and many abandoned farmlands with unclear ownership. These farmlands have been abandoned for years, and it becomes challenging to find the owners, either because of aging of farmers or a lack of successors. Future research should consider different types of abandonment when discussing this question.
4.2. Conclusions
This study revealed the spatial patterns of farmland abandonment and analyzed its determinants in 2015 from geographical and socio-economic aspects by employing global (OLS) and local (GWR) regressions. Based on the former municipality boundaries, spatial patterns of farmland abandonment and its determinants were displayed and discussed. The main conclusions are as follows:
Firstly, farmland abandonment in Japan displays an uneven pattern and strongly corresponds to the country’s geographical condition and regional agricultural development. While taking the farmland abandonment rate as the measure, a nation-wide distribution of abandoned farmland is firstly displayed. We found that most abandoned farmland is concentrated in the Chugoku Shikoku, Kanto, Kyushu and Chubu regions, in contrast to other regions that have good agricultural conditions, such as the Hokkaido and Tohoku regions.
Secondly, rather than geographical factors, socio-economic variables have a much higher explanatory ability. Household-related variables, such as the arable land ratio of self-sufficient farm households, displayed the most significant positive correlation with farmland abandonment, and non-successor farm households were positively correlated with farmland abandonment. In contrast, the arable land area per farm household and the laborers per farm household were negatively correlated with farmland abandonment. For farmland-related variables, paddy field density exhibited a significant negative correlation with farmland abandonment.
Thirdly, determinants of farmland abandonment are spatially varied regarding local geographical or socio-economic circumstances. Local regression showed its superiority in terms of explanatory ability and goodness of fit for our best model. In short, farmland abandonment is a complex process driven by interactions of multiple determinants. Even within one region, the determinants might be different depending on specific local circumstances.
Finally, in regard to suggestions to prevent further abandonment on the one hand, the Japanese government should institute some new policies or taxation reforms to help farm households, especially self-sufficient farmers, to re-cultivate their land or to allow them easily transfer their land to land-holding cooperatives that have sufficient laborers [
23]. Japanese policy on rice production and import restrictions play a key role to keep paddy fields in Japan. As such, policies regarding rice market are crucial for maintaining farmland. On the other hand, farmers should seek more economical pathways to survive. For instance, in terms of non-successor farm households and aging farmers, in order to solve the lack of laborers, strengthening community-based farming, building farmland banks [
64] and agricultural networks could be effective countermeasures to prevent future abandonment.