Climate change and migration across the Great Wall of China during the Little Ice Age

This study examines migration across the Great Wall of China in response to climate change in Chinese history during the Little Ice Age (1500−1850 ad) and assesses the effectiveness of the Great Wall as a barrier based on the push-pull theory. It empirically analyzes the spatiotemporal patterns of migration across the Great Wall based on datasets on precipitation, temperature, population size, and migration events. Here we show that more migration events occurred during the cooling climate period. Furthermore, more migrants came from farther north to cross the Great Wall during dry periods. These results imply the general ineffectiveness of the Great Wall in blocking migration. The findings serve as a reminder that if human survival is threatened (e.g., by climatic events), barriers may not successfully block migration. Thus, evaluating the effectiveness of barriers in accordance with the stressors of migration is important when applying the push-pull model.