1. Introduction
Food security is the basis of national security, and the most basic condition for achieving food security is guaranteeing basic self-sufficiency in food. Cultivated land resources are the foundation of self-sufficiency in food [
1,
2]. Xi Jinping, the General Secretary of the Communist Party of China’s Central Committee, stressed that China’s rice bowls should mainly contain Chinese grain, and cultivated land is the lifeblood of food production. As such, cultivated land should be protected in the same way that pandas are protected, and the country should strictly guard and defend the red line of the 1.8 billion mu of cultivated land. That land provides the basic requirements of cultivated land resources. The state has already issued a series of policies to protect the cultivated land, in view of the cultivated land loss problem in the urbanization process. However, the implementation effect of these policies has not had the expected effects. In particular, the rapid development of China’s economy, the acceleration of urbanization, the decrease in the amount and quality of cultivated land, the ecological deterioration [
3,
4,
5] and the problem of food security have aroused extensive attention, both at home and abroad [
6,
7,
8]. L Brown even posed the question “Who will feed China?” It was in this context that the idea of the security of cultivated land resources was put forward [
9], a topic that gradually became the focus of the government and academia [
10]. Very few studies directly examine the security of cultivated land resources (SCLR) in foreign countries. Similar studies have mainly focused on food security [
11,
12,
13], sustainable agricultural development in developing countries and regions [
14], as well as the changing amount of cultivated land under the background of land-use and land-cover change [
15,
16,
17]. Other studies have analyzed the driving forces of land use change and cultivated land change [
18,
19,
20], sustainable soil management [
21], as well as the protection of agricultural land [
22,
23,
24]. These studies have shown that land occupation is an important threat to food security in the EU. In India, the mismatch between water supply and agricultural water demand is the real cause of food insecurity. The security of cultivated land quantity all over the world has been affected by war, the economy and policies. Biophysical and socio-economic proximity have been the main influencing factors of cultivated land change, and population density has been negatively correlated with cultivated land expansion. Zoning and differential taxes are commonly used to regulate the loss of farmland in urban development. However, zoning by itself does not seem to be sufficient to protect cultivated land; zoning needs to be implemented in conjunction with other policies, such as improving land prices. At the same time, there is a necessity to study land quality, the ecological sustainable development of land use and the growing problem of environmental degradation in agricultural areas [
25]. The European Commission has taken a number of measures and actions to protect soil including a 50% reduction in the use of chemical pesticides, a 20% reduction in fertilizer use plus a decrease of nutrient losses by at least 50%, a minimum of 30% of the EU’s land area as protected areas, a limit on urban sprawl, a reduction in the pesticides risk, 25% of the EU’s agricultural land put forward as organically farmed and a reduction in land degradation and planting [
21]. These ambitious measures and targets can provide a reference for the selection of quality and quantity security indicators of cultivated land resources. Such studies would help to formulate more effective sustainable development policies.
With the declining amount of cultivated land in the urbanization process and the emergence of food security issues, domestic scholars’ research has focused on the evaluation of the SCLR and the influencing factors. The main contents of such studies are as follows: (1) The concept of SCLR. At present, no unified standard of the concept of SCLR has been formed. Most of SCLR is explained from the perspectives of natural attributes, such as the quantity, quality and ecology of cultivated land, as well as the social attributes, such as the guarantee of social and economic development. For example, Zhu Hongbo maintained that SCLR is the expansion and extension of the concept of cultivated land protection; SCLR is also a state in which the cultivated land resources owned by a region can guarantee the security of the regional cultivated land itself, as well as the region’s social and economic security, food security and ecological security [
3]. Song Wei et al. believed that SCLR refers to the state and ability of cultivated land resources to guarantee the survival and development of human society and to promote the harmony and balance of an ecological system. This can only happen when a country’s or region’s cultivated land resources are effectively protected. That protection can be divided into the three aspects of quantity safety, quality safety and ecological safety [
10]. (2) Regarding the evaluation of SCLR, previous research has focused on the two aspects of index system building and evaluation methods. The former mainly constructs theoretical frameworks from the connotation of SCLR, or establishes an evaluation index system reference to some model framework. The latter mainly includes an index system of quantity–quality–ecological security, resources–environment–economy–society, nature–economy–society–ecology, an evaluation system of pressure–status–response (PSR), etc. For example, Wang Fang et al. [
26], Liu Shenghuan et al. [
27] and Wu Yanfei et al. [
28], respectively, established index systems to evaluate SCLR in suburban Guangzhou, Hubei and Anhui provinces from the perspectives of the quantity, quality and ecology of cultivated land. Kuang Lihua et al. constructed a cultivated land system security index system from the systematic perspective of the “trinity” of cultivated land quantity, quality and ecology [
29]. Li Nan et al. evaluated the SCLR in Liaoning Province from a spatio-temporal scale perspective. The study selected the four major indexes of resource, environment, economy and society [
30]. Song Ge et al. extended resources and environment into nature and ecology and constructed an SCLR evaluation index system from the four aspects of nature, economy, society and ecology [
31]. Liu Xue et al. used a PSR framework to construct an evaluation index system of land resources security in Chongqing [
32]. Ren Jiaqiang et al. used a PSR model to construct an evaluation index system for the SCLR in Liaoyang County, Liaoning Province [
33]. Cai Yinying et al. used hidden danger, state and immunity models to construct an evaluation index system of cultivated land ecological security to analyze the ecological security of cultivated land resources in Jianghan Plain [
34]. The evaluation methods of SCLR mainly include an analytic hierarchy process [
4], an improved TOPSIS model [
29], a comprehensive index method [
10], an abrupt progression method [
30], and a weighted comprehensive evaluation method [
35]. Among the above, the comprehensive index method is the most widely used and the most mature. (3) Regarding the driving force of cultivated land resource security, the main driving factors behind quantity security are policy, economic development, non-agricultural construction and population growth [
36,
37,
38,
39]. The main factors that influence quantity security are the unused land area per capita, the area of supplementary cultivated land per capita, the area of cultivated land per capita, the protection awareness of cultivated land, etc. The factors that influence ecological security are obviously different, due to different levels of economic development [
40,
41].
In conclusion, scholars have conducted numerous studies on SCLR from different perspectives, and they have achieved fruitful results. This provides a foundation for further research on SCLR. However, the academic circle has not yet reached a consensus on the definition of SCLR, and the current SCLR evaluation index system does not have any broad and unified recognition standard. Most existing studies have evaluated SCLR based on the PSR model; many studies analyze single factors, such as quantity security [
36,
42], quality security [
43,
44] or ecology security [
34,
41]. Secondly, SCLR evaluation methods show a trend of diversification. The entropy weight method and analytic hierarchy process are more extensive in the weight calculation, but the entropy weight method is more objective. In terms of numerical calculation, the most widely used and mature method employed is the composite index method. In addition, China’s cultivated land resources have obvious differences in time and space. Therefore, it is necessary to explore the dynamic changes of SCLR from the perspectives of time and space, so as to provide a basis for the further improvement of cultivated land protection policies. China’s total grain output in 2019 was 6.64 × 10
8 t, the highest output level in the country’s history. The proportion of grain output in the main food producing areas rose to 78.89%, and the contribution rate of grain increased to 93.91% [
45]. Based on historical changes and growth trends, increasing China’s grain yield in the future will mainly depend on the main food producing areas [
46]. As one of the main food-producing areas in China, Hubei Province has a reputation of “when two Hu (Hunan and Hubei) are ripe, China is sufficient”. SCLR is particularly important in Hubei. Therefore, the entropy weight method, the composite index method, the obstacle degree model and the spatial analysis method are employed to probe the spatio-temporal characteristics and obstacle factors of SCLR. The objective is to provide a certain reference in the choice of evaluation method. Meanwhile, with regard to the SCLR evaluation index system, this article added a “water resources per unit land area” indicator, according to the actual situation in Hubei Province, to construct a comprehensive evaluation index system that can provide a reference for further study of SCLR. This will also provide theoretical reference for differentiated policies that ensure SCLR in Hubei Province.
2. Study Area
Hubei Province, referred to as “E”, is run through by the Yangtze River and the Han River. Hubei is known as the “province of a thousand lakes” and “the land of fish and rice”. The provincial capital is Wuhan. Hubei is located in central China, adjacent to Anhui in the east, Chongqing in the west, Shaanxi in the northwest, Jiangxi and Hunan in the south and Henan in the north. Hubei is about 740 km long from east to west, and 470 km wide from north to south, with a total area of 185,900 square kilometers, or 1.94 percent of China’s total area. Within the province, mountains account for 56% of the total area, hills account for 24% and plains and lakes account for 20%. At present, the province has jurisdiction over 13 prefecture-level administrative regions, including 12 prefecture-level cities and one autonomous prefecture: Shiyan City, Yichang City, Enshi Tujia and Miao Minority Autonomous Prefecture (Enshi City), Xiangyang City, Jingmen City, Jingzhou City, Suizhou City, Wuhan City, Huangshi City, Ezhou City, Xiaogan City, Huanggang City and Xianning City (
Figure 1). In addition, four county-level administrative units are directly under the province’s jurisdiction.
By the end of 2018, the total cultivated land area was 5235 square kilometers, accounting for 3.66 percent of the total cultivated land in China. The province has designated 58.88 million mu of permanent basic farmland and 31.64 million mu of high-quality cultivated land; the latter accounts for 40 percent of the total cultivated land. Cultivated land per capita is 1.3 mu, which is lower than the national average level of 1.52 mu. Hubei is rich in water resources; lakes are mainly distributed in the Jianghan Plain. Currently, there are more than 700 lakes, with a total surface area of 2706.851 square kilometers. Lakes with a total surface area of more than 100 square kilometers include Honghu Lake, Changhu Lake, Liangzi Lake and Futou Lake. In 2019, the total population of Hubei Province was 59.27 million, of which 36.1547 million were urban residents, and 23.1553 million were rural. Hubei’s GDP was 4.582831 trillion yuan, up by 7.5% from the previous year. Urban residents’ and rural residents’ per capita disposable income were 37,601.3 yuan and 16,390.9 yuan, respectively. Hubei Province is one of the 13 main food-producing areas in China. The province’s grain output was 27.25 million tons in 2019, or 4.1% of the national grain output. Clearly, Hubei plays an important role in ensuring China’s national food security.
5. Conclusions and Policy Implications
5.1. Conclusions
(1) The SCLR in the Hubei Province presents obvious spatial-temporal differences. The security degree of cultivated land resources showed an upward trend from 2010 to 2019; the security degree gradually improved throughout this period. Quality security and ecological security both showed an upward trend, while quantity security showed a downward trend. The security of cultivated land resources decreased from west to east. The spatial pattern of quantity security was high in central Hubei, low in eastern Hubei and lower in western Hubei. The spatial pattern of quality safety was high in central Hubei, low in eastern and western Hubei. On the whole, the spatial pattern of ecological security was higher in the west and lower in the east; overall, the level of ecological security increased slightly; the areas with higher security levels continued to maintain higher levels, while the areas with lower security levels gradually declined.
(2) The main obstacles to quantity security are the reduction rate of cultivated land area, food production per capita, cultivated land area per capita and urbanization level. The main barriers to quality security are water resources per unit area of land, GDP per capita, the total power of agricultural machinery and the per capita net income of rural residents. In addition, obstacle factors had certain differences in different regions. The main obstacle to quality security in Shiyan, Enshi and Yichang in western Hubei is the total power of agricultural machinery. The centralized treatment rate of sewage is also one of the main obstacles to ecological security. The main obstacles to quality security in central Hubei are the per capita net income of rural residents and the ratio of effective irrigated area. Pesticide load per unit area was the main obstacle to ecological security. The main obstacle to quality security was water resource per unit area of land; forest coverage was the main obstacle to ecological security in the east of Hubei. The main obstacles to quantity security showed little difference in western, central and eastern Hubei. This study’s conclusion is that the main factors that affect SCLR are natural factors, such as cultivated land area and water resources, as well as urban development, the perfection of agricultural infrastructure, the application of pesticides and chemical fertilizers and other human factors.
5.2. Policy Implications
(1) Policies and measures should be formulated to ensure SCLR on the bases of quantity, quality and ecological security. In terms of quantity, cultivated land protection policies should be further strengthened to ensure the area of cultivated land per capita, Also, cultivated land conversion should also be strictly controlled; the rate of decrease in the cultivated land area must be reduced and the protection of high-quality cultivated land around cities and towns must be strengthened. In terms of quality, appropriately scaled farming should be encouraged, to increase the overall productivity of cultivated land, as well as improving the soil condition and the fertility of cultivated land, strengthening the investigation and monitoring of cultivated land quality, as well as increasing farmers’ per capita income and GDP per capita. Ecologically, green agriculture should be developed. The Hubei Province should rationally adjust the production structure of agriculture, reduce the load of pesticides per unit area, reduce industrial SO2 and solid waste output, and reasonably delimit cultivated land ecological protection areas, according to the ecological suitability of cultivated land. Finally, the investment in ecological and environmental governance should be increased appropriately.
(2) Differentiated policies should be formulated for the protection of cultivated land in different regions. Western Hubei should strengthen its protection of quantity security and strictly control cultivated land conversion. Central Hubei should focus on strengthening ecological security protection. For example, crop rotation and fallow could be implemented in Xiangyang, Jingzhou and other regions with large areas of cultivated land, as a means to protect the cultivated land ecosystem. Eastern Hubei should strengthen its protection quality and ecological security of cultivated land. Measures should be formulated to protect the quality of cultivated land, and to improve and restore degraded cultivated land. In the meantime, these measures should encompass protecting and rationally utilizing water resources and improving farmland irrigation areas. In regions where the quality security of cultivated land is not high and where the economy is relatively developed, such as Wuhan and Ezhou, farmers should be encouraged to engage in socialized agricultural production services. Finally, large-scale, mechanized and digital operations should be promoted, and priority should be given to the protection of land fertility and appropriately scaled operations.
5.3. Study Limitations
According to the reality of abundant water resources in the Hubei Province, in this study, the index of water resources per unit area of land is selected in the construction of an evaluation index system. This approach, using the comprehensive index method and the obstacle degree model, has a certain novelty compared with other related studies. As can also be seen from the results, water resources per unit of land have an important impact on SCLR. The proposed policy suggestions have certain reference significance for the sustainable utilization of cultivated land resources. However, this study only took 13 prefecture-level cities in the Hubei Province as research objects and only conducted research from the provincial and municipal perspectives. The study fails to study SCLR at the county scale, and policy suggestions have not yet been refined, due to restrictions on the availability of data. In addition, this study only collected statistical data from 2010 to 2019; the authors will continue to collect data with longer time series in the future, in order to better reveal the dynamic changes of SCLR using longer time series. Finally, due to data and technology limitations, only ArcGIS is used for spatial analysis and the visualization of results. Remote sensing data will be used for further research in the future.
In summary, this article aimed to probe the spatio-temporal characteristics and obstacle factors of SCLR in the Hubei Province, including from the perspective of quantity, quality and ecology. However, SCLR is also affected by factors such as cultivated land culture, and in the future, we will conduct further studies on the selection of indicators to improve the index system, and improve the security degree of the cultivated land resource.