Spatio-temporal evolution and obstacle diagnosis of human settlements based on the "production-living-ecological" functions.

Sustainable development is a hot topic of global concern and sustainable human settlements (HS) are crucial to people's happiness. Thus, strengthening the construction of HS will help enrich human settlements geography with theories of HS interactions, clarify the existing problems of the Chengdu-Chongqing urban agglomeration (CC), promote the harmonization of the human-land relationship, and realize the SDGs. The results were as follows. (1) the quality of HS exhibited an upward trend with diminishing disparities in PLE functions. (2) A spatial layout featuring the high quality of HS in the east and west and low quality in the central areas was identified, with Chengdu and Chongqing serving as two high-value core areas. (3) The evolution of the quality of HS levels to achieve a leapfrog shift was challenging and the spatial spillover effect and phenomenon of "club convergence" were evident. (4) Living function was a primary obstacle at the criterion layer and indicators within production function became major obstacle factors at the element layer. These findings have enriched the research scope of human settlements geography from the scale of urban agglomerations, and provided scientific decisions for the SDGs.