Industrial agglomeration, environmental protection, and high-quality economic development: evidence from cities along the Yellow River Basin of China

China’s economy has entered a new phase of development, but ecological and environmental issues continue to hinder the quality of economic development. Meanwhile, the externalities of industrial agglomeration are seen as essential for promoting high-quality economic development. This article proposes a theoretical framework to examine the relationship between industrial agglomeration, environmental protection, and high-quality economic development. Using cities along the Yellow River Basin as the research object, a spatial econometric model is employed to verify the hypothesis. Ultimately, the conclusions are as follows. First, there is a significant U-shaped curve relationship between industrial agglomeration and high-quality economic development, as well as between environmental protection and a high-quality economy. Industrial agglomeration plays a significant role in promoting environmental protection. Second, high-quality economic development exhibits spatial spillover effects under both spatial weight matrices, while industrial agglomeration and environmental protection only show spatial spillover effects based on geographical distance spatial weight matrices. Finally, the article suggests that cities should accelerate the degree of industrial agglomeration to achieve the dual effect of promoting environmental protection and high-quality economic development. Additionally, governments should pay special attention to inter-regional synergistic mechanisms when fostering ecological protection and high-quality economic development.