Farmland Dynamics and Its Grain Production Efficiency and Ecological Security in China’s Major Grain-Producing Regions between 2000 and 2020

Understanding the land use/cover changes associated with agricultural production is essential for food security in increasingly urbanizing areas. Such studies have been widely conducted in different regions of China; yet, its major grain-producing regions (MGPRs) remain less studied. To address this knowledge gap, we conducted analyses of the land use conversion matrix, spatial hot spots, decoupling, and index evaluation from a spatiotemporal perspective, to quantify the MGPRs’ farmland changes and its grain production efficiency and ecological security during 2000–2020. The results showed the following: (1) Farmland in the MGPRs experienced a net decline of 2.54 × 104 km2, with significant spatial heterogeneity in the area, extent, and speed of loss/gain. (2) Farmland gain came from mostly forest, grassland, and unused land, with hotspots in northeastern China, while farmland loss increasingly changed to construction lands, with hotspots covering east-central China and in the suburbs surrounding capital cities. (3) Grain production in the MGPRs increased by 1.6 times in the past 20 years, via its strong decoupling from farmland quantity in especially central-eastern China. (4) Land ecological security in the MGPRs was less secure but has been improving with non-homogeneous regional differences, while it demonstrated a spatial pattern of “higher security in the north–south and lower in the middle”. Our findings suggested that China’s MGPRs would continue to lose farmland and China’s food security should require a sustainable decoupling of grain production and farmland quantity while maintaining ecological security. This study has significant policy implications for farmland conservation in China’s MGPRs, as well as highlighting the landscape sustainability opportunities of urbanization-associated farmland loss in densely populated human–environment systems in general.