Mangrove forests are vital and unique ecosystems, crucial for biodiversity conservation, coastal protection, and climate regulation. Nevertheless, threats to mangroves from climate change and human activities are rising. This study examined how different plant growth phases respond to climate fluctuations using medium-resolution remote sensing data in Google Earth Engine (GEE) via satellite (Sentinel-2 and Landsat)-derived vegetation indices. Five vegetation indices for two main mangrove species found in Iran: Avicennia marina and Rhizophora mucronata were evaluated during a 30-year span from 1993 to 2023. Based on this research, the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Phenology Index (NDPI) are the most appropriate indices for capturing the distinct phenological responses of individual mangrove species. Using NDVI, the start, end, and peak of the growing season for both species, occur in September, May, and January, respectively; however, there are small differences in peak days for different species. The time-series data analysis showed that throughout the past three decades, the growing season length (spanning from September to May) has decreased approximately by 1-2 days for both species, However, the patterns differed between species: A. marina's growing season advanced by 6-7 days (both start and end), while R. mucronata's was delayed by 1-2 days. The decline in growth length and changes in the start and end of growing season are attributed to altered precipitation patterns including changes in the timing (start and end), intensity and total amount of rainfall and high temperatures. Our results show that growth cessation during the hottest months coincides with periods when daily maximum temperatures exceed 29 degrees C, as reported by regional climate data. The results of the GAM analysis revealed distinct climatic sensitivities across species, with R. mucronata showing a stronger response to minimum temperature and precipitation than A. marina. The research emphasizes the significance of vegetation index selection for accurate monitoring of the impact of climatic variations on mangrove species considering different periods (growing season, non-growing season, spring, summer, fall, and winter). Furthermore, this study revealed the effectiveness of using multi-spectral medium resolution satellite imagery for assessing individual tree species phenology and highlighted the crucial necessity for focused conservation initiatives to reduce the impacts of climate change and protect important coastal habitats, particularly regarding the influence of climate change on mangrove ecosystems in semi-arid areas.