Telecoupling indirect ecological impacts of urban expansion in China from the perspective of the food trade

A comprehensive evaluation of the ecological cost of urban expansion is crucial for preventing ecosystem degradation and improving ecosystem governance. However, the indirect impacts of urban expansion through cropland displacement are grossly underestimated, particularly the spillover effects on distant regions. This study proposed a telecoupling framework for the total indirect ecological losses (TIEL) of urban expansion. It was divided into the near losses (NIEL) and distant losses (DIEL), depending on whether cropland displacement occurs inside or outside the region. An inter-provincial network of DIEL can also be constructed by ecological impact embodied in food trade with other regions. We found that approximately 80% of urban expansion occurred on croplands, which caused indirect loss of 86,586 km(2) of ecological land through cropland displacement in China during 2000-2019. The total indirect ecological losses were 8.4 times greater than direct losses at the average of all provinces. Food trade induced more serious indirect ecological losses owing to the higher yield difference between encroached cropland import regions and new cropland in export regions. The proportion of DIEL in TIEL was more than 50% in developed regions such as Beijing, Shanghai, Tianjin, and Jiangsu. The distant impacts of urban expansion in the eastern coastal provinces were mainly transferred to north-eastern China and the rest of the world. This study identified the teleconnection between local urban development and distant environments and infromed inter-regional ecological compensation policies to mitigate regional inequalities.