Dynamics of agricultural system vulnerability to climate change and the externalities of its mitigation in China

China is one of the countries where the agricultural system has been significantly affected by climate change. Reduced agricultural labor, water shortages, and carbon emission restrictions bring more challenges to China's agricultural system vulnerability to climate change. Quantifying and visualizing agricultural system vulnerability to climate change could provide targeted decision-making suggestions for agricultural production in different regions. However, the effectiveness and externalities of strategies to deal with agricultural system vulnerability to climate change required a long-term historical process to test. Therefore, this study explored the long-term vulnerability dynamics of agricultural systems to climate change since China’s reform and opening up. The agricultural system vulnerability assessment model used in this study integrated socioeconomic-based assessment method and biophysics-based assessment method. In the context of declining and aging agricultural labor and not obvious increase in grain sown area, the alleviation of the vulnerability of China's agricultural systems to climate change benefited from the high-intensity input such as fertilizers, pesticides, irrigation, agricultural plastic films, agricultural machinery. Although agricultural machinery effectively compensated for the risks caused by the migration and aging of agricultural labor, it was not advisable to continue to strengthen mechanized production within the current sowing area due to the significant reduction in the marginal substitution rate of machinery to labor. In the process of mitigating agricultural system vulnerability, the water consumption and carbon emissions of agricultural production are multiplied. Increased water consumption resisted the impact of drought on agricultural system vulnerability, but agricultural production was helpless in dealing with waterlogging. It was difficult to increase grain yield by intensifying water consumption and carbon emissions under current climatic conditions. To further reduce agricultural system vulnerability to climate change, the challenges of how to adjust the cropping system to adapt to climate change, how to deal with the impact of meteorological disasters on agricultural production, and how to avoid excessive non-grainization of cropland should be addressed. The resolution of these issues will help the developing countries that are in the process of industrialization and urbanization to coordinate the relationship between agricultural modernization, labor migration, carbon emissions, and water consumption when responding to agricultural system vulnerability to climate change.