Spatio-temporal evolution and layout classification of facility agriculture land in urban agglomerations of China

The development of facility agriculture is a crucial pathway for implementing the Greater Food concept. Being aware of the spatio-temporal evolution and distributional characteristics of facility agriculture land is essential for optimizing its spatial layout and ensuring the successful implementation of national food security strategies. In this study, we constructed a three-dimensional classification framework of “Human-Land-Region” for facility agriculture land in urban agglomerations of China, focusing on matching the number of people with the amount of facility agriculture land, and coordinating the spatial layout of facility agriculture land. The study taken the 19 national-level urban agglomerations in the 14th Five-Year Plan as the study area, and calculated the land area for facility agriculture, per capita area, geographic concentration, and the Moran’s I of the 19 urban agglomerations during the period of 2013-2021. Then we can get the spatio-temporal evolution characteristics of facility agriculture land and the evaluation results of the three-dimensional framework in urban agglomerations on the global scale. On this basis, taking into account the comprehensiveness and scientific city of the typical cases in terms of the three-dimensional evaluation results, geographic zoning, and the development level of the urban agglomerations, the four urban agglomerations of the Central Plains, Chengdu-Chongqing, the Yangtze River Delta, and the Mid-southern Liaoning were finally identified as the typical cases. The study applies the modified gravity model, core-edge analysis and other methods to explore the characteristics of the gravitational relationship of facility agriculture development among cities within these four urban agglomerations, and realizes the study of facility agriculture land at a downscaled scale from the whole situation to the inner part of typical urban agglomerations. The findings indicate that facility facility agriculture land in China’s urban agglomerations decreased by 445,900 hectares between 2013 and 2021. The reduction shows a regional divergence, in which the Northeast and Central regions shared smaller scales of facility agriculture land, while the South generally had more extensive areas than the North. From 2018 onwards, the distribution of facility agriculture land shifted from a highly centralized to a slightly decentralized pattern. In various periods, urban agglomerations exhibiting “high-high clustering” and “low-high clustering” were predominantly found in the eastern regions, demonstrating significant spatial dependence, while other areas showed more dispersed distributions. According to the “Human-Land-Region” analysis framework, the layout of facility agricultural land in urban agglomerations in China can be divided into four types: “Growing population with reduced and decentralized lands”, “Growing population with increased and centralized lands”, “Shrinking population with reduced and centralized lands” and “Shrinking population with reduced and decentralized lands”. Urban agglomerations with the first type have seen relatively slow development in facility agriculture, with a weakening industry pull, while those with the second type have achieved large-scale operations through the concentration of resources. These two main types account for a total of 73.68%, which is the leading type of facility agricultural land in China's urban agglomeration. The study reveals a severe reduction in the scale of facility agriculture land over the past decade, with a spatial divergence from population changes. Recent trends show a shift from centralized supply towards risk diversification, with an increasing focus on establishing perennial vegetable plots in medium and large cities. Future planning should address the balance between local production and external supply, and strategically design facility agriculture within urban agglomerations to enhance the resilience of the supply chain.