Transmission pathways of China's historical climate change impacts based on a food security framework

There are still many uncertainties about how climate change affects the development of human society. The impact of climate change is likely to be weakened or amplified by the response and adaptation of the reciprocal feedback process after entering the socio-economical subsystem. The study of the climate change impact processes is the basis for understanding the mechanisms of climate change impacts. Furthermore, long-term research of climate change impacts can provide historical similarity and experience for current or future adaptation of climate change. Ancient China was traditionally an agricultural country. Its food production safety, food supply safety, and food consumption safety reflect the impacts of climate change being transferred from a production subsystem to a population subsystem to an economic subsystem. Based on a conceptual framework of food security, we selected 10-year resolution sequences of grain harvest grades, famine indices, and economic levels in China over the past 2000 years (206 BC-AD 1911) to quantify and recognize the main transmission pathways of climate change impacts during cold and warm units of climate change. Our results were as follows: (1) according to the transmission relationship climate change -> grain harvests -> famines -> economic levels, there are 16 main transmission pathways, including 10 pathways starting from cold units and 6 pathways starting from warm units. (2) The main pathway is dominated by natural factors and socio-economic factors, with each factor set accounting for approximately 50%. However, the probability of the main pathways with socio-economic influence leading toward negative developments was 60% for cold units, and the probability of the main pathways with socio-economic influence leading toward positive developments was 66.7% for warm units. According to the main pathway led by natural factors, of all transmission pathways in cold units (100%), 14.7% of the depressed economy may be more directly related to climate change. However, 32.3% of the prosperous economy may have a more direct relationship with climate change in warm units (100%). (3) Famine is the most important link in the climate change influence on transmission chains regulated by socio-economic factors. Famine reflects both poor harvests due to the natural production subsystem and a lack of grain allocation by the socio-economic subsystem or the government's ability to eliminate famine. Thus, there may be another pathway of transmission, such as climate change -> agricultural yield/grain production -> economic prosperity -> famine relief (social vulnerability).