1. Introduction
Since the reform and opening up, the economic and ecological ties between regions in China have become closer. Regional trade has become an important way for many areas to meet the local consumption demands. The growing inter-regional economic ties have brought about the allocation and embodied flow of resources and environmental elements over a larger area. Such transfer has further led to a new phenomenon of inequality between regions, that is, environmental inequality. Previous scholars have found evidence of global inequality stemming from the embodied land and water trade [
1]. Therefore, studying the resources and environmental elements embodied in China’s inter-provincial economic ties is of great significance for correcting the imbalance between regional economic development and ecological responsibility, and further, promoting the high-quality development of China. Agricultural land is the ecological basis for human survival and the resource basis for socioeconomic development. Analyzing the occupancy and transfer of agricultural land embodied in inter-provincial economic ties helps to further clarify the mutual ecological responsibilities between regions, establish a horizontal agricultural ecological compensation system, conduct more targeted land use management, and promote the sustainable development of agricultural ecology.
In accounting for land transfers embodied in trade, many scholars have successively proposed concepts such as the ecological footprint, virtual land, virtual farmland, and embodied agricultural land to describe the impact of human consumption demands on land resources [
2,
3,
4,
5]. Early research mainly focused on virtual land research and ecological footprint studies. Virtual land is a quantitative measurement of the land resources embodied in trade production. This method is mainly based on the land occupancy coefficient of the unit of agricultural products and processed products, and the land resource occupancy of land resources is measured in combination with the output and trade transfer volume. This only measures the direct land resource used in the product, generally for agricultural products. As an example, from the perspectives of producers and consumers, Qiang et al. measured the trade in “virtual land” of crops and processed products in China from 1986 to 2009 [
6]. The results showed that the crop trade between China and other countries had saved a lot of land globally. Yawson demonstrated a simple food balance approach to estimating virtual land use in the 2050s and found that the UK could face large virtual land use due to its imports, made necessary by the country’s small land area [
7]. The use of the virtual land method can also be found in many other studies [
8,
9,
10,
11,
12]. The concept of the ecological footprint was proposed by Willian E. Rees in the early 1990s [
13]. This method is mainly used to measure the consumption of natural ecosystems by human activities and convert that into a unified comparable land or water area, including the impacts associated with trade. The National Footprint Accounts (NFA) by the Global Footprint Network (GFN) calculate the ecological footprints embodied in national trade by multiplying the footprint yield coefficient (t/ha) with the mass volumes of traded goods between countries from the United Nations Statistics Division (UNSD) global trade database, to create a “product land use matrix (PLUM)” [
14]. Daniel et al. as an example, applied the PLUM approach to measuring the biophysical value of international trade flows [
15].
However, virtual land methods and traditional ecological footprint methods have limitations in tracking the end-use of products, and they cannot measure land occupation caused by service provision. The ecological footprint model based on input–output analysis inherits the advantages of the traditional model and makes up for the shortcomings of the traditional model in revealing the true location and interconnection of the land footprint [
16]. At the same time, it can effectively avoid making repeated calculations of the footprint components [
17,
18], meaning it is favored by researchers. Using the combination of input–output models and land footprints, many scholars have studied the flow of land resources embodied in global trade, including global demand–supply chains or the trade of certain agricultural products [
19,
20]. Due to China’s important position in world trade, many studies have explored the virtual land or arable land resources embodied in China’s trade [
21,
22,
23,
24,
25], and some researchers have also estimated the forest land [
26] or pasture land [
27] embodied in the exports and imports of China. At the same time, further scholars have discussed the land resources embodied in international trade by other countries, such as Belgium, Spain, and Finland [
28,
29,
30]. In addition to the study of land resources embodied in trade or the demand–supply chain, another research feature using input–output models is the study of the water–energy–food/land (WEF) nexus embodied in international trade or food products’ trade [
31,
32,
33,
34,
35]. The WEF nexus can more comprehensively reflect the flow of natural resources embodied in the connections of human economic activities and thus has greater guiding significance for the realization of regional sustainable development [
36].
Most of the above studies were based on the land or other resources embodied in global trade or the resources embodied in a country’s foreign trade. It is rare to pay attention to the land resources embodied in the economic ties among regions within a country. For a large country like China, however, that is important. Certain previous studies paid attention to this issue. For example, Shan et al. analyzed the cultivated land resources embodied in the inter-regional economic connections in the Beijing–Tianjin–Hebei region, to illustrate the issues of inequality and collaboration around a northern Chinese urban agglomeration [
37]. Guo et al. [
38] and Chuai et al. [
39] both, meanwhile, studied virtual built-up land transfers embodied in China’s inter-regional trade.
In summary, the existing literature on China’s embodied land research focused on foreign trade, analyzing the flow of embodied land at the global spatial scale, industry characteristics, and driving factors [
40]. Relatively few researchers studied the embodied land at the inter-provincial level in China, and the research was mainly on the virtual farmland of food trade, assessed through agricultural product measurement, while there was a lack of research on embodied land in the inter-regional economic relationship, as explored using the input–output method. To date, there are certain limitations to how the embodied land of inter-provincial trade is in terms of research scale, methods, and objects, while research on the virtual water flow has developed to become more mature [
41,
42]. Research on the embodied land behind China’s inter-provincial economic ties urgently needs to be further developed and the topic explored in depth. In that context, this paper presents a model of China’s inter-provincial agricultural land footprint, as determined via the agricultural land footprint method and the inter-regional input–output method. This article focuses on the relationship between regional land resource endowment, economic development, industries/sectors, and the agricultural land footprint. At the same time, it analyzes the size of China’s agricultural land footprint at different levels of inter-provincial economic ties, and further analyzes the spatial transfer pattern of embodied agricultural land, revealing the embodied agricultural land footprint behind the inter-provincial supply-demand chain and economic connection. The findings provide a scientific basis for clarifying the mutual ecological responsibilities of different regions, enriching the research on embodied land at the inter-regional level, and promoting the sustainable development of agriculture.
4. Conclusions and Discussion
This article took the embodied agricultural land footprints between provinces in China as a starting point to calculate the complete agricultural land footprint and the net agricultural land footprint, to understand the distribution and transfer of agricultural land footprints. The main conclusions are as follows: (1) There were obvious differences between the direct agricultural land occupation and direct agricultural land footprint in each province. Higher direct agricultural land occupation does not necessarily lead to a higher direct agricultural land footprint. The direct agricultural land footprint of regional agricultural economic activities in relatively developed and populated areas was greater than the direct occupation of agricultural land, while the opposite was true in economically underdeveloped areas, i.e., the former was significantly smaller than the latter. The direct agricultural land occupancy coefficient was generally higher in areas with lower levels of economic development. (2) The agricultural land footprint of areas with a higher level of economic development was generally higher than that of areas with a lower level of economic development. The external footprint of developed regions such as Beijing, Tianjin, and Shanghai was much larger than the local footprint, while the underdeveloped regions such as Xinjiang, Ningxia, and Gansu showed the opposite. Agriculture, food manufacturing, and tobacco processing were the main industries that caused the agricultural land footprint of each province. The sum of those accounted for more than 60% of the total agricultural land footprint that year, and there were large differences in the agricultural land footprint structure of industries between provinces. (3) The embodied agricultural land transfer structures of various provinces were quite different. For example, among the four provinces of Hebei, Henan, Shandong, and Jiangsu, where the total transfer amount was relatively high, Hebei and Jiangsu were balanced, while Shandong was the net transfer-in type, and Henan was the net transfer-out type. The embodied agricultural land transfer between regions showed two main directions, on the whole, the one is from north to south, the other one is from west to east, which reflects the transfer law from the less developed regions to the developed regions.
Overall, most of the regions with higher economic development levels are net imports of agricultural land. This indicates that agricultural land in developed regions cannot support its own end-use and needs to maintain its economic development by importing agricultural products. On the contrary, the economically underdeveloped areas are mostly net exporters of agricultural land, especially some provinces with a large proportion of agricultural activities, such as Henan and Sichuan provinces, which have sufficient agricultural land and can provide agricultural products for the final use of other provinces. Assuming that there is no difference in value increase between agriculture and other industries, the above situation will not lead to further widening of the regional economic gap. However, if the price of agricultural products has been maintained at a lower level than that of other industries, the spatial shift pattern of the above agricultural land footprint will lead to the expansion of regional differences. Research has shown that the price of agricultural products in China has always been in a disadvantageous position relative to the price of industrial products and services [
48]. Therefore, the agricultural land transfers among regions within China are actually the transfer of wealth, which is not conducive to the reduction of regional economic differences. On the other hand, due to the decrease in the income of agricultural land, farmers may exacerbate the unsustainable use of agricultural land in order to increase their income. Some scholars have found that global agricultural trade has had a negative impact on the global land ecosystem since around 2000 [
49]. Therefore, in order to improve the level of sustainable land use, policy-makers should also pay attention to the transfer of agricultural land.