In recent decades, the Zagros vegetation region has experienced increasing extreme events and intensifying climatic stress, which have reduced forest stability and accelerated forest decline. This study aimed to project trends in extreme climate indices from 2030 to 2060 and evaluate their implications for forest decline. Outputs from the NorESM2-LM model under three emission scenarios (optimistic, intermediate, and pessimistic) were downscaled to analyze 27 standard extreme climate indices, classified into five groups (absolute, threshold, percentile, duration, and other indices), across 18 meteorological stations. The projections indicate that mean temperature will reach 14.3, 14.6, and 15.4°C under the three scenarios, respectively. Mean annual precipitation is estimated at 537, 555, and 537 mm, respectively. Of 486 examined trends (18 stations × 27 indices), 163, 96, and 9 are projected to be significant under the three scenarios, respectively. Percentile-based indices are projected to show the highest frequency of significant trends, with 52, 34, and 4 significant trends, respectively. In the semi-arid climate zone, 18 and 35 trends are expected to be significant from 2030 to 2060 under the intermediate and pessimistic scenarios, respectively. Continued changes in extreme climate indices are expected to intensify forest decline. These projected changes may increase climatic stress on Zagros forests, particularly under pessimistic conditions, by intensifying temperature extremes, altering precipitation patterns, and increasing the frequency of dry periods, thereby reducing forest resilience and increasing vulnerability to further future forest decline. Therefore, management of Zagros forests requires continuous monitoring of extreme indices and appropriate strategies to prevent further forest decline.