The effect of volcanic gas has been intensifying in Tateyama Mountain since the Great East Japan (Tohoku) Earthquake in 2011. Volcanic gas is absorbed by vegetation and living beings including adverse impacts. This gas emission is unfavorable for visitor’s health, losing tourist attraction and affecting sight-seeing activity. Thus, it is significant to analyze the impact of volcanic gas on vegetation. Remote sensing data are required to monitor the effects of volcanic gas emissions, classify vegetation types, and detect damaged vegetation. In this study, the spatial dispersion impacts of fumarolic gas on alpine vegetation decline are evaluated using time-series remote sensing imagery. A decline in the summer green and evergreen vegetation has been observed from 2009 to 2024 using the support vector machine algorithm (SVM) technique. The prediction of the extended affected area was calculated by MaxEnt modeling. The models identified the responsible environmental factors for the future extinction of the vegetation in Tateyama, i.e., climatic and geographic layers. The model showed the possible future declining area due to the responsible environmental factors. The results suggest that management officials to focus on the probable declining area to take necessary steps to protect the vegetation in Tateyama.