Climate change is an environmental challenge with effects on natural systems. The Hiv and Shalamzar watershed in the southern Alborz slopes, possessing species Astragalus, Thymus, Achillea, Glycyrrhiza, Cichorium, Hypericum, and Alhagi persarum, are rich in medicinal plants. Despite studies, no comprehensive systematic review has been conducted. This research aimed to collect, evaluate, and synthesize findings on climate change impacts on ecological capacity of medicinal plants in these watersheds. This systematic review followed PRISMA guidelines. A search was performed in domestic and international databases. The time frame was 2011–2024 for Persian and 2015–2026 for English articles. After screening, 60 studies were selected for final analysis. Data were analyzed using thematic analysis and descriptive statistics. Annual temperature increased by 1.2°C and growing season precipitation decreased by 15% over three decades. Density of Astragalus, Thymus, and Achillea declined by up to 25%. Flowering of Cichorium occurred 10-15 days earlier, and Glycyrrhiza shifted to higher altitudes (2500-3000 m). Active compounds including alkaloids, flavonoids, and essential oils decreased by up to 30%. Alhagi persarum faces severe habitat reduction in eastern Alborz. Highland areas as climate refugia prevented up to 40% of population decline. It is predicted that by 2031, 30% of medicinal plant distribution area will be lost. Climate change has reduced ecological capacity. Species vulnerability, altitudinal shifts, reduced active compounds, and threats to Alhagi persarum are consequences. Overharvesting by local communities has accelerated extinction rates. Management of climate refugia, sustainable cultivation development, awareness, and adaptation programs are essential for preserving these resources.