Island carrying capacity for three development types: ecological resource, agricultural production, and urban construction.

The evaluation of island carrying capacity is the premise for conducting the island spatial planning and can contributes to guiding island ecological conservation and socioeconomic developments. In this study, the island carrying capacities were evaluated for the three major development types, namely, ecological resource, agricultural production, and urban construction, based on the quantity and quality. The occupancy and vacancy rates of island carrying capacity were measured in different scenarios. Miaodao Archipelago and Dongtou Archipelago in China were selected as the study area to demonstrate the evaluation. The former is constituted all by spatially isolated rocky islands, while the latter is featured by the coexistence of the sandy and rocky islands and the connection with the mainland by bridges. The results indicated the high variances of occupancy and vacancy rates of island carrying capacity at multiple spatial scales. Across the two archipelagos, climate conditions, island composition, and spatial connections with the mainland controlled the spatial variance at this scale. For different types of islands, the sandy island presented distinctly higher occupancy and vacancy rates for agricultural production than the rocky islands. At the single island scale within the same archipelago, the developments of agricultural production and urban construction distinctly increased with the increase in the island area. The dependency of island constructions on the external world in Dongtou Archipelago was higher than that in Miaodao Archipelago. Meanwhile, the difference in traffic conditions between the two archipelagos did not distinctly influence the food dependency on the external world. Then, practical suggestions in terms of quantity control and quality promotion were proposed to improve the island carrying capacity.