Progress and major themes of research on urban shrinkage and its eco-environmental impacts

Urban shrinkage is the process of population loss, industrial and functional decline, and eco-environmental deterioration due to various natural and human factors that occur once a city's development reaches a certain point. It is an external manifestation of positive or negative changes in an urban economy, society, culture, resource use, and sustainability. Urban shrinkage is a new feature of global urbanization as well as a frontier of international and Chinese research. It has attracted widespread attention from academics in China and overseas, becoming an emerging trend that has spread from developed countries to underdeveloped ones. Research on and responses to urban shrinkage have also become new tasks of China's new urbanization strategy. Our review of the existing literature reveals that there are significant temporal and spatial differences in research by Chinese and overseas scholars on urban shrinkage. Urban shrinkage studies have paid scant attention to interactions with the eco-environment, with analyses of urban shrinkage mechanisms and factors largely focusing on economic and social development factors; and urban shrinkage index analyses have tended not to include eco-environmental quality and environmental pollution indicators. The key tasks for future urban shrinkage research include the following: to conduct in-depth research on the mechanisms and driving factors of urban shrinkage to reveal the essence of urban shrinkage; to discover the principles behind interactions between urban shrinkage and the eco-environment, as well as to analyze the eco-environmental effects of urban shrinkage; to construct an index system for evaluating the extent, monitoring and providing warnings of, and containing urban shrinkage; and to research urban shrinkage coping strategies under different circumstances and carry out experiments and demonstrations according to local conditions.