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Forage supply has been stressed due to the rapid increase in China's livestock consumption. However, the long-term dynamics of the relationships between forage demand and multi-sourced supply are not understood. Here, we examine the annual forage demand, or practical carrying capacity (PCC), and supply, or theoretical carrying capacity (TCC) from 2000 to 2019 in China. We construct a forage supply-demand index (FSDI) to represent the forage supply pressure using MODIS-derived net primary productivity products and provincial statistical datasets, and we consider two scenarios. First, natural grasslands are the sole source of forage. Second, natural grassland forage supply is supplemented with straw crops. We find an increase in PCC in northwestern China's major pastoral and agropastoral provincial regions, including Inner Mongolia, Gansu, Ningxia and Qinghai, at rate of 0.24-3.59 million sheep units (SU) a year. As the primary source of forage, the theoretical carrying capacity of natural grasslands (TCCgrass) expanded at a rate of 3 million SU/yr nationally. Crop straws fed 126.58 million SU nationally in 2019, which accounted for 11.3% of the total practical carrying capacity and alleviated the forage supply pressure by reducing FSDI by 26.56%. During 2000-2019, the theoretical carrying capacity of straw crops (TCCcrop) increased rapidly from 76.5 million SU to 126.6 million SU, which accounted for 10%-15% of the total forage supply at the national scale. We also discovered large carrying capacity gaps (TCCgap) in the northwestern pastoral provincial regions of Inner Mongolia, Xinjiang, Gansu, and some agricultural provinces such as Shandong and Henan, when we considered forage supply from both natural grasslands and straw crops. Our findings showed a large forage gap in the traditional pastoral regions, and we also discussed green fodder as a potential solution for balancing the supply of and demand for forage, which may shed light on crop and forage planning.
Yang et al. (Wed,) studied this question.