**1. Introduction**

Cultivated land resources are the foundation of rural development and provide residents with important basic living materials such as grain, vegetables, and oilseeds [1,2]. However, with the occurrence of rapid urbanization and industrialization worldwide, an increasing amount of rural agricultural land is occupied by non-agricultural land (such as residential land, roads, industrial land, etc.) [3,4]. The serious non-agriculturalization of cultivated land has caused problems such as food crises and the intensification of social contradictions. This has been demonstrated in studies conducted in China, Iran, and Indonesia [5–7]. As a result, the issue of the non-agriculturalization of cultivated land has been the focus of study in the fields of land science and rural sustainable development [8,9].

Many scholars have conducted research on the quantitative evaluation of the nonagriculturalization of cultivated land, the influence of the non-agriculturalization of cultivated land on the social economy, and the driving mechanism and management measures of cultivated land conversion [10–12]. Questionnaire surveys, spatial autocorrelation, and gravity models are widely used in the quantitative evaluation of the non-agriculturalization of cultivated land [13,14]. Studies have shown that the non-agriculturalization of cultivated land provides a spatial condition for urbanization and industrialization, but also leads

**Citation:** Han, H.; Peng, H.; Li, S.; Yang, J.; Yan, Z. The Non-Agriculturalization of Cultivated Land in Karst Mountainous Areas in China. *Land* **2022**, *11*, 1727. https://doi.org/10.3390/ land11101727

Academic Editors: Yongsheng Wang, Qi Wen, Dazhuan Ge and Bangbang Zhang

Received: 19 August 2022 Accepted: 2 October 2022 Published: 5 October 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

to a decline in the amount of cultivated land and food shortages, ultimately resulting in an increasingly intensifying contradiction between food security and economic development [15,16]. Urbanization, industrialization, economic benefits, and national management policy are the driving factors of the non-agriculturalization of cultivated land at the macro scale [17–19]. The livelihood changes and income levels of farmers due to cultivated land conversion play an important role in non-agriculturalization at the micro scale [20,21]. In addition, numerous studies have found that the reform of land administration systems and the promotion of "compact" urban development can effectively alleviate the conversion of cultivated land to non-agricultural land [9,22]. Current research focuses on suburbs or rural areas characterized by rapid economic development, whereas there is little concern for underdeveloped rural mountainous areas. Moreover, the conversion of cultivated land to non-agricultural land strongly changes the land-use structure, which changes the rural ecological environment. However, the impact of the non-agriculturalization of cultivated land on the ecological environment has not yet been reported. Due to the interference of various complex human activities, developing countries with rapid economic development face the serious non-agriculturalization of cultivated land, which has a profound impact on food security.

As the most populous country in the world, China's cultivated land resources are relatively scarce, and the protection of cultivated land is an important task for land resource management [23]. Under the influence of China's rapid economic development, the problem of the non-agriculturalization of cultivated land caused by its occupation by built-up land is very prominent [11]. Simultaneously, blind deforestation and cultivation on steep slopes have caused serious soil erosion and frequent natural disasters in China over the past few decades. The Grain for Green Project, which was initiated in 2000 and aims to improve the quality of the ecological environment, has been implemented against the backdrop of the continuous rise in the national yield for staple grains. It encourages the conversion of a significant portion of sloping cultivated land to ecological land (forestland, shrubland, and grassland), which exacerbates the non-agriculturalization of cultivated land [15,24]. The Grain for Green Project has been primarily implemented in the karst mountainous regions of southwestern China, which are typical ecologically sensitive areas [25]. Furthermore, the rural economy in karst mountainous areas has significantly improved as a result of the influence of western development policies [26]. However, the lack of land resources in karst mountainous areas has caused a significant proportion of rural labor to migrate to cities, thereby disrupting the stability of the cultivated land landscape (such as cultivated land abandonment) and altering the ability of karst mountainous areas to maintain their natural landscapes. Furthermore, cultivated land has been converted into other high-yield non-agricultural land as a result of the conversion of farmers' livelihoods and the decrease in economic income from cultivated land [27,28]. While the quantification of land-use changes would aid in the understanding of the general characteristics of the conversion between different land-use types, it would not explain the mechanism by which cultivated land is converted to non-agricultural land, especially on a small scale.

According to the dominant landform types, four townships in southwestern China's Guizhou Province with different landform types were selected as typical representatives. The objectives of this study include the following: (1) to quantify the rate of conversion of cultivated land to non-cultivated land in karst mountainous areas; (2) to explore the slope gradient and spatial heterogeneity of the non-agriculturalization of cultivated land in karst mountainous areas; and (3) to analyze the correlation between the non-agriculturalization of cultivated land and landscape ecological risk. This study provides a reference for the protection of cultivated land and may help to clarify tradeoffs between the societal targets of land and the impacts of land-use changes in karst mountainous areas.
