Spatiotemporal analysis of cropland production and its trade-off with climate regulation across China

إنجليزي. The World Food Summit and the Paris Agreement have highlighted the vital need to sustain food production and to mitigate the effects of climate change. This represents a pivotal moment in the development of present and future agricultural and food systems, further emphasized by the United Nations' 2015 pledge to achieve Zero Hunger (SDG 2) and Climate Action (SDG 13) as key elements of the Sustainable Development Goals (SDGs). Global food security is increasingly at risk due to various challenges, including population growth, rapid urbanization, unsustainable resource use, and the negative effects of climate change on crop production, despite improvements in agricultural productivity. These problems are worsened by changing diets that favor resource-intensive foods, resulting in substantial environmental damage and highlighting the crucial link between farming practices and sustainability. Cropland plays a crucial role not only in food production but also in providing essential ecosystem services, thus contributing significantly to several SDGs. This emphasizes the urgent need to adopt sustainable farming practices in the face of growing land-use conflicts. Furthermore, it is critical to integrate technological innovations and interdisciplinary research to improve land management strategies. This thesis carefully investigates China's unique position in the global agricultural landscape, analyzing the complex tradeoff between food security and environmental sustainability using various data sources, including earth observation datasets, statistical analyses, and academic literature. China's rapid urbanization has led to substantial changes in agricultural land-use patterns, particularly in main grain-producing areas like the Yangtze River Basin. These changes have significant implications for China's agricultural production and its crucial role in the global food supply chain, highlighting the need for sustainable farming practices to address the growing demand for global resources. Chapter 2 explores strategies of cropland intensification and large-scale utilization to meet China's growing food demand. It utilizes the Logarithmic-Mean-Divisia-Index (LMDI) analysis, along with statistical and land cover data, to assess the impact of cropland intensification (i.e. crop yield and Multiple Cropping Index) and large-scale utilization (i.e. Mean Parcel Size and Number of Parcels) on crop production at both national and local scale. The analysis indicates that advancements in agricultural technology and management practices that increase yield and enable multiple harvests per year can significantly boost crop production. This is essential for overcoming the logistical and environmental challenges associated with diverse cropland sizes and ensuring food security. The chapter concludes that, notwithstanding these obstacles, optimizing yield and implementing multiple cropping can be crucial in sustainably meeting China's growing food needs. Chapter 3 examines spatial temporal dynamics of cropland abandonment and recultivation between 2000 and 2020 across the Yangtze River Basin. Using remote sensing, the study reveals a notable trend of cropland abandonment, particularly in regions in regions characterized by gentle slopes. Notably, a substantial proportion (74%) of this abandoned land has been recultivated for agricultural purposes, demonstrating the region's resilience and adaptability in land use. This chapter presents novel insights into dynamics of agricultural land use, offering a foundation for future research and policy recommendations aimed at restoring abandoned cropland and fostering sustainable farming methods. The results emphasize the crucial role of policy support, technological advancements, and adaptive farming practices in promoting the recultivation of abandoned lands. Based on cropland abandonment and recultivation maps conducted in Chapter 3, Chapter 4 explores the tradeoffs between cropland production and climate regulation. The study reveals that, using the Carbon Sequestration module of InVEST model (Integrated Valuation of Ecosystem Services and Tradeoffs), cropland abandonment led to a substantial increase in carbon stock, storing an additional total of 182.3 million tons of C between 2002 and 2020. Nevertheless, this environmental benefit comes at the cost of a 13.47 million ton decrease in grain production. Spearman correlation analysis revealed a significant trade-off at the provincial level between carbon stock change and grain yield change, further analysis indicated diverse impacts across regions at grid level. This study highlights the pressing need for policies that can balance the dual goals of climate change mitigation through enhanced carbon storage and food security through optimized grain production. The findings support the development of refined land management practices that carefully equilibrate environmental benefits and agricultural productivity. Overall, this thesis contributes to the discourse on sustainable land use planning in China, providing empirical evidence and strategic insights to address the complex challenges of ensuring food security, enhancing crop production efficiency, and mitigating climate change impacts.

2. Zero hunger

13. Climate action