Along with rapid economic growth, many natural regions, meadows, farms, etc. have been converted into unbridled urban areas. Urban development converts natural areas into districts full of buildings leading to disrupted ecological balance of the ecosystem. The carrying capacity (CC) of urban ecosystems needs to be estimated because they require large amounts of materials and energy as well as the ability of pollutant absorption in a small location. The amount of material and energy used in

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... s may be more than of that provided by urban CC. High consumption rate is associated with high levels of contamination that transcends the UCC. Therefore, the CC of the urban environment and its population capacity must be evaluated for urban development planning. Materials and Methods: In this study, UCC load number within the pressure-state-impact-response (PSIR) framework and 20 indicators were used to evaluate the CC and pressure on the urban ecosystem of Semnan. Results: According to the results, the load number in the district 1 was equal to 180.05with a low to moderate pressure on the urban ecosystem. The load numbers in districts 2 and 3 were respectively 230.41 and 272.86 imposing a moderate to high pressure on urban ecosystem. Conclusions: Because of the greater population density in the District 3, materials and energy consumption and waste production was higher leading to a higher pressure on the urban ecosystem.