Urbanization is a major trend both in developed and developing countries today. Although one argument for tropical forest conservation is dependency of people on the forests for their livelihoods, rural depopulation may diminish its significance. In this study, we assessed population changes from the 1980s to 2000s in rural villages of Sarawak, Malaysia by questionnaire surveys. Contrary to our expectation, population growth rates were higher in forest-rich villages than in less-forested villages. Then we assessed potential factors for population growth rates; they were (a) forest cover, (b) original population size, (c) proportion of villagers living outside the village in the 1980s, (d) education level, and (e) household wealth. We found (c) was the most important, and highly correlated with that in the 2000s. This indicates that many villagers live outside while leaving their families or keeping their village membership in growing villages. In addition, (a) and (d) were positively and negatively associated with the growth rates, respectively. People with less education and chance to get stable income in a city may keep their village membership if the village still has good forest cover, which functions as a safety net. This study indicates the significance of rural forests in the age of urbanization.