Maximum carrying potential of cultivated land in Shaanxi Province of China under different living standards

Carrying capacity (potential) of food security can be assessed to align with the vision of the United Nations Sustainable Development Goal 2 (SDG 2) to 'end hunger, improve nutrition and promote sustainable agriculture.' This study aims to evaluate the maximum carrying potential of cultivated land, according to nutritional demands at different living standards and cultivated land productivity. Firstly, the evaluation models were applied to the production potential of cultivated land, including light-temperature production potential, climatic production potential, and the maximum yield of regional crops. The nutrient output model was combined after evaluation. The evaluation factor was conventionally transformed into a more reasonable output of nutrients using grain quantity. Taking the Shaanxi Province as the study area, the cultivated land production potential was evaluated under different scenarios. Subsequently, the nutrients and dietary structures (plant-only and plant-animal diet) under three living standards (subsistence, moderate prosperity, and affluent level) were selected to calculate the cultivated land carrying capacity and its index. Additionally, the improvement points of cultivated land production capacity were obtained to further clarify the pure grain and comprehensive output of cultivated land in 2023. Finally, the population of cultivated land was also evaluated under the living standards using the Bucket Theory. The results show: (1) The cultivated land provided 5 751.360 trillion kJ of energy, 39.82 trillion grams of protein, and 11.507 trillion grams of fat under the maximum yield of regional crops, which were 2.50 times, 2.88 times, and 1.55 times higher than the actual output level in 2023, respectively. The production potential of energy, protein, and fat shared the spatial agglomeration and hierarchical differentiation. (2) The maximum carrying capacity of cultivated land reached 672.36 million people at the subsistence level; there were 218.19 million people under the maximum yield of regional crops. Once the nutrient constraints were considered, the fat was served as the limiting factor for the maximum cultivated land carrying potential. There was great variation in the carrying capacity derived from cultivated land output and the limiting nutrient factors under the mixed plant-animal dietary structure. Specifically, the nutrient-restricting factor was shifted from fat to energy. The most attainable carrying potential of cultivated land was 50.1209 million people under the nutrient constraints at the affluent level, as calculated under Output Scenario III. (3) High carrying potential occurred in Northern and Central Shaanxi, with no overload over any living standard or dietary structure. Counties and districts in Yulin exhibited an increasing trend in carrying potential under nutrient constraints. This was attributed to the capacity of food to supply nutrients. (4) Cultivated Land Carrying Capacity Index shared the significant spatial heterogeneity with a Z-shaped distribution: A cluster with high values was found in Guanzhong, Southwestern Shaanxi, and Central Northern Shaanxi; a cluster with low values was concentrated in Western Shaanxi and Northern Yulin. The theoretical threshold was quantified for the carrying potential of cultivated land resources in Shaanxi Province, fully meeting the living standards and nutritional needs. The research findings can provide a strong reference to support food security in the stage of affluent life.