This study aimed to investigate the driving factors behind functional shifts in rice fields and to assess the contribution of rice field activities to greenhouse gas emissions. Data were collected from 58 respondents, including heads of subak systems, agriculture officers, representatives from the Tabanan Department of Agriculture and Horticulture, and academicians. Leverage analysis, Interpretive Structural Modeling (ISM), and emission calculations using the 2019 IPCC approach were employed, along with time series data from 2016 to 2020. The findings revealed that the primary determinants of functional shifts included pest attacks and diseases, rice field selling prices, availability of production facilities, housing needs and tourism growth in the study area, family participation in rice field management, marketing institutions, enforcement of awig-awig subak (penalties for rice field conversion), and the conditions of irrigation canals and roads to the farming area. Emission analysis, focusing on methane, demonstrated that the reduction in rice field area due to functional shifts between 2016 and 2020 led to a 21.95 percent decrease in greenhouse gas emissions.