Multi-Sensor Evaluation of Quantitative and Qualitative Dynamics of Urban Green Infrastructure in a Semi-Arid Climate (Case Study: Mohajeran)

These days, semi-arid and arid cities in Iran are struggling with a conflict between physical development and ecological capacity. In these areas, high rates of evapotranspiration and reduced rainfall pose a serious threat to the survival of green infrastructure. This study evaluates the quantitative and qualitative dynamics of green infrastructure in the new city of Mohajeran between 2018 and 2024 using a multi-sensor approach within the Google Earth Engine (GEE) platform. Sentinel-2 satellite imagery was utilized for quantitative assessment, while Landsat 8/9 data were employed for qualitative and thermal analysis. The Vegetation Health Index (VHI) was extracted by integrating the Vegetation Condition Index (VCI) and Temperature Condition Index (TCI) to model the physiological stress of plants. The results revealed that the area of urban green infrastructure significantly decreased from 75.53 hectares in 2018 to 57.28 hectares in 2024. Despite this substantial reduction in area, the mean VHI showed negligible change (from 0.40 to 0.41), indicating relative qualitative stability within the remaining green patches. However, the decline of the minimum VHI value to 0.21 in 2024 signals the emergence of critical stress hotspots in certain areas. The findings demonstrate that Mohajeran’s green infrastructure has transitioned from a stage of physical development to a phase of "qualitative crisis" and spatial contraction. Consequently, urban management must shift its focus toward prioritizing thermal resilience management and optimizing the health of existing infrastructure.