Material Metabolism of Infrastructure on An Inhabited Island: Resource Flow and Stock Growth

Analyzing the material metabolism of infrastructure provides insights into resource flow and accumulation, offering policymakers new perspectives on resource management and planning. This study comprehensively analyzed the material stock (MS) of infrastructure on Miao Island using a bottom-up approach and Pleiades stereo images. Key findings include: (1) in 2020, the total in-use MS was 249.8 kt, with stone, gravel, and sand accounting for 80%. Transportation infrastructure held the largest share (40.8%), followed by non-residential buildings (30.1%), residential buildings (26.7%), and pipeline infrastructure (2.4%); (2) Stone and wood are abundant resources on the island, whereas steel, ceramics, aluminum, and glass are entirely dependent on external supply; (3) Over the past 40 years, the MS has grown significantly, with a net addition stock of 179.6 kt (256% growth). Development periods from 1980-1990, 2000-2005, and 2015-2020 were closely linked to China's reform and opening-up, infrastructure stimulus plans, and local government policies; (4) Compared to urban areas, Miao Island has lower construction intensity, with a per capita MS growth rate of 10.12 t/yr versus the national average of 13 t/yr. The steel stock in residential buildings is 15.62 kg/m², only 37.82% of the urban average. However, the potential conversion of infrastructure stock into waste still poses a significant challenge to the island's environmental carrying capacity.