1. Introduction
Cultivated land is an important cornerstone of agricultural production. In the 21st century, global cities continue to expand rapidly [
1]. Excess urban expansion of the city causes the mass loss of high-quality farmland, directly threatening global food security. Especially in economically underdeveloped areas such as Asia and Africa, grain pressure and shortages of cultivated land become unavoidable practical problems. In addition, a modern economy and rapid development lead to a rigid growth in global grain demand [
2,
3]. Meanwhile, the competition for cultivated land resources in industry, agriculture, and other fields is increasingly fierce, which further aggravates the human-land conflict. Poor cultivation and management also cause prominent problems, including overuse, abuse, soil degradation, environmental pollution, and so on. These problems hinder the realization of sustainable development goals (SDGs) [
4]. Moreover, the world is currently in the post-epidemic era. Combined with the impacts of sudden events such as extreme climate change and geopolitical conflicts [
5], the stability of the global grain system is being severely challenged. Thus, the CLUT is not only the core issue of land use and cover change (LUCC), but also an urgent need to respond to the increasingly complex situation of cultivated land protection in the world.
The concept of land use transition (LUT) was first proposed by British scholars when studying forest cover changes in underdeveloped countries [
6]. LUT refers to the trend variations or transitions of land use morphology driven by socioeconomic transition and innovation during the corresponding period [
7,
8]. Early studies mainly focused on the forest land use transition and gradually expanded to the transition of other types of land with the deepening of the research [
9,
10,
11,
12]. Since cultivated land is the most basic agricultural resource, research on the CLUT has continued to receive high attention from academic circles. Some scholars conducted relevant studies on the CLUT based on different regional scales and perspectives. Guan et al. [
13] analyzed the spatial transition of farmland use in Kyushu, Japan, from the perspective of spatial morphology, mainly focusing on changes in the quantity and spatial pattern of cultivated land. Song et al. [
14] and Zhang et al. [
15] have constructed a theoretical analysis framework for the multifunctional transition of farmland use and proposed an optimization path for the multifunctional use of farmland. Zhang et al. [
16] explored the spatiotemporal pattern and trend variations of the CLUT in different regions of Africa and found that the CLUT had obvious spatiotemporal differentiation characteristics. Ketema et al. [
17] assumed that economy, technology, system, and location were the potential drivers of the CLUT in Europe, but the impact of labor force change and social culture were easily overlooked. Ke et al. [
18] constructed a research framework for the green transition of farmland use and conducted an empirical analysis on the example of Hubei Province, China. Moreover, in the context of rapid urbanization, several studies have also explored the coupling relationships among CLUT, economic development [
19], rural construction [
20], and grain output [
21]. However, most of the existing studies focused on a single perspective, such as spatial transition and functional transition, lacking innovative and multiple perspectives. Meanwhile, existing research has given greater consideration to the process, characteristics, and driving factors of the CLUT, while insufficient regard has been given to the effect and optimization regulation of the transition. At present, it can be inferred that the field of CLUT still exists with an enormous development space in the aspects of empirical evaluation, method innovation, impact exploration, etc. Therefore, it is particularly important to promote the development of transition research to a higher and deeper level.
China has the largest population in the world, as well as the largest food production and consumption. Over the past 20 years, with the rapid advancement of industrialization and urbanization in China, occupying a large amount of farmland for non-agricultural construction has become a common phenomenon in developed regions [
22]. At the same time, integrated urban-rural development and the flow of geographical factors have also caused prominent issues such as non-agriculturalization [
23], non-grain [
24], marginalization, and fragmentation of cultivated land [
25,
26], which seriously threaten the grain security of China. In the context of the severe situation, the academic community called for a reconsideration of the use of cultivated land resources. At the beginning of the 21st century, Long [
27] introduced relevant theories of LUT into China and improved them according to the current situation of land use management in China. Related research results were significant for the sustainable use of cultivated land resources and national food security. Moreover, intensive study on the CLUT was also conducive to coordinating the protection of cultivated land resources, high-quality economic development, and ecological civilization construction, which attracted wide attention from society and government.
Due to the late start of research on the LUT in China, there were few direct studies on the topic of CLUT, whereas the relevant researche mainly focused on themes of driving mechanisms and morphology transition. As everyone knows, China has a vast territory with diverse natural, economic, and social elements. Thus, although previous studies of driving mechanisms have involved many scales, such as provinces, cities, counties, and river basins, it is still crucial to clarify the transition process and its spatial heterogeneity at the national scale. In addition, cultivated land use is a complex system composed of multiple elements that interact and influence each other. These elements are interwoven according to certain rules and principles. They together constitute the overall function and structure of cultivated land use. However, few scholars have studied the coupling and coordination relationships between different elements. Since human-land conflict is prominent in China, the analysis of the CLUT is inseparable from the in-depth analysis of the coupling influence of the changes in various cultivated land use elements within the human-land system. Based on this, this study took the perspective of cultivated land use morphology as the starting point. Then, the coupling coordination degree model was used to explore the spatiotemporal pattern of the CLUT in China from 2000 to 2019, and the coupling coordination types were further divided. Finally, by identifying the main driving factors of the utilization transition and their spatial differentiation, the study proposed some corresponding policy recommendations, aiming to provide decision-making references for the protection and optimal utilization of cultivated land.
4. Discussion
The spatiotemporal evolution pattern and driving mechanism of CLUT are the hot topics in the field of cultivated land use research in China. The research results indicate that the spatial structure, functional intensity, and management model of cultivated land use are closely related to the cultivated land use morphology, which has strong explanatory significance for the CLUT. The change in cultivated land use morphology is the result of socio-economic development and the transformation of cultivated land use modes in China’s modernization process. On one hand, China’s industrialization and urbanization development have led to changes in the traditional elements of cultivated land use. In order to meet major development needs, such as food security, high-quality agricultural development, and rural revitalization, cultivated land utilization is shifting towards a more efficient direction, and spatial differences are also narrowing. On the other hand, the spatial distribution and coupling coordination of CLUT constantly evolve and change over time. The impact of natural conditions, socio-economic factors, and land policies on the CLUT varies greatly over different periods. Analyzing the spatiotemporal differences in the impact of different factors on the CLUT can provide a basis for scientific management and control of cultivated land resources. Research also suggests that China should start with the following aspects to promote efficient transformation of cultivated land use and achieve agricultural modernization in the future:
- (1)
Take multiple measures to promote comprehensive land remediation across the entire region. Resource endowment is the foundation of the CLUT. At present, the negative effect of the topography is more intense in western China, mainly due to the complex terrain, fragile ecological environment, relatively poor cultivated land resources, and high degree of cultivated land fragmentation. Comprehensive land consolidation is of great significance for the improvement of terrain constraints and large-scale operations. It has become an important level for high-quality agricultural development and rural revitalization in China. However, the following two points should be paid attention to: Firstly, it is necessary to fully utilize advanced scientific technology and management methods. On one hand, we can use advanced technologies such as mechanical deep planting, buried drip irrigation, soil testing, fertilizer distribution, or drone spraying to control plant diseases and insect pests and standardize the planting. On the other hand, equipment such as aerial drones and ground sensors can be used to establish remote control and three-dimensional monitoring systems. Secondly, we need to strengthen the dominant position of farmers in the consolidation process. We should fully respect the wishes of farmers, understand their practical demands, and encourage them to actively learn the skills of modern agricultural production, which can provide an internal driving force for the transition.
- (2)
Actively support and guide the cross-regional operation of agricultural machinery. The total power of agricultural machinery played a role in promoting the CLUT, but its effect continued to weaken with time, and problems of regional and structural imbalance were prominent due to the inefficient allocation of agricultural machinery resources. Since the implementation of agricultural preference policies such as agricultural machinery purchase subsidies, the number of agricultural machines in China has continued to expand. Agricultural machinery is abundant in some areas, but as far as the country is concerned, there are still many areas lagging behind. Therefore, actively guiding the cross-regional operation of agricultural machinery can effectively promote the allocation of agricultural machinery resources. In recent years, the income from the cross-regional operation of agricultural machinery has decreased. In order to effectively reduce the burden on farmers, we should increase targeted subsidies for agricultural machinery oil and further innovate value-added services such as green channels for agricultural machinery refueling, agricultural preference commodity counters, convenient service desks for agricultural machinery, etc. In addition, the operation link should be appropriately widened to promote the transition from traditional harvest to whole-process management, specialization, and one-stop service.
- (3)
Implement the responsibility of cultivated land protection and form a joint cultivated land protection system. The construction land demand index played a certain role in promoting the CLUT, mainly thanks to the strict cultivated land protection system. Although the central government has issued the strictest policies and systems around the control, construction, and incentives of cultivated land, there is a lack of a strong incentive mechanism for the triple protection of cultivated land. To this end, we should refine the trinity protection scope of cultivated land, divide the evaluation threshold based on the characteristics the resource background and create an intelligent, dynamic supervision platform to provide support for farmland improvement and differentiated management. Meanwhile, elements related to farmland protection should be included in the scope of supervision, such as strict supervision of chemical fertilizers, pesticides, and other inputs, as well as farmland ecosystem and biodiversity protection. Moreover, it is necessary to explore the establishment of a horizontal and vertical linkage compensation mechanism for farmland protection to reduce the risk of environmental damage caused by cross-regional supplementary farmland and stimulate the spiritual and material effects of the subjects responsible for farmland protection [
65].
Although this study can comprehensively reflect the level and characteristics of the CLUT, which is significant for empirical research, the cultivated land use system is a complex giant system with open characteristics, and the indicator system for structure, function, and model transformation still needs to be improved. Especially as the tasks and goals of China’s cultivated land protection will change over time, it is necessary to continuously adjust the evaluation indicator system to adapt to the changes in China’s food security situation. In addition, the analysis of the spatiotemporal evolution characteristics of CLUT is only a preliminary result. Based on the significant differences between regions, in-depth analysis of the regional suitability and applicability of CLUT should be the content that needs further deepening research in the future.