Abstract
Rapid urbanization and population growth in China have raised great concerns regarding food security caused by the loss of limited cultivated land. In this study, we used remotely sensed data and an agricultural productivity estimation model to characterize the spatiotemporal patterns of the conversion of cropland into urban land and quantify its impacts on agricultural productivity potential during China’s rapid urbanization period, from 1990 to 2010. The results show that urban development has transformed approximately 4.18 Mha, or 2.26%, of the total cropland in China. From 1990 to 2000, approximately 1.50 Mha of cropland was developed, while roughly 1.8 times this amount (2.68 Mha) was converted over the period of 2000 to 2010. Most of the conversion is located in the central and eastern coastal provinces and is mainly concentrated on the periphery of the major urban areas. The transformation has, consequently, caused a 71.45 Tg, or 2.65%, loss of potential light-temperature agricultural productivity (PLTAP); losses were 24.33 Tg in the first decade of the study and 47.11 Tg in the second. At the provincial scale, the largest percentages of PLTAP loss are mainly concentrated in the developed provinces on the eastern coast, such as Shanghai, Beijing, Zhejiang, Tianjin, and Jiangsu. Considering that these areas can accommodate more people and produce higher economic output on unit area of built-up land and, yet, scarce land that can be reclaimed, this study suggests that the dynamic balance of total farmland policy in China should be varied provincially according to the major function of the province. The policy adjustment will help maximize the utilization efficiency of land.
Highlights
Since the late 1990s, the process of urbanization in China has accelerated
To characterize the spatiotemporal patterns of the conversion of cropland land into built-up land, land use data derived from Landsat TM/ETM+ images were collected from the National Resources and Environmental Scientific Data Center (RESDC) of the Chinese Academy of Sciences (CAS)
In the following two subsections, the spatiotemporal patterns of urban land developed from cropland are depicted in detail, and how this conversion has impacted agricultural productivity potential is analyzed
Summary
The annual average rate of urbanization in this period is three times as rapid as that from 1949 to 1990 (Figure 1, [1]) This rapid urbanization could affect the national food supply and has attracted great concern from the Chinese government, due to the combination of a vast population and a scarcity of available cropland per capita. Since the 1990s, the government has promulgated a series of strict policies to respond to these impacts, including basic farmland protection regulation in 1994 and a dynamic balance of total farmland policy in 1998 These policies have alleviated national cropland loss, according to statistics from the Ministry of Land and Resources, cropland in China has decreased by 69.31 × 104 ha per year since the late 1990s [2]. Tracking the impacts of urbanization on cropland and agricultural productivity is a prerequisite to better guarding the food supply, especially as China is predicted to continue its rapid urbanization over the few decades
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