Internal migration in rural Benin is not directed to the southern coastal regions as in many neighbouring countries. Instead, peasants from the densely populated and environmentally critical northwest of Benin are engaging in a process of agricultural colonization of the central region. Consequently, the predominant approach to understanding these processes of internal population movement in Benin is to focus on environmental degradation. But why do people stay in degraded areas while others leave? Why do migrants again leave the environmentally still stable destination areas and why does migration itself becomes causation for new migration? It is obvious that one needs a structural understanding of the environment in the political and cultural context of this region to understand its role as a driver for migration. On the basis of an empirical case-study the impact of progressive deterioration of environmental conditions is embedded in social and cultural structures. Being aware of this is necessary in order to really understand a migration pattern that at first glance could be misconstrued as being purely environmentally induced. Since migration theories are somehow overlooked in the debate on environment and forced migration the empirical findings will be embedded in a theoretical approach that places greater emphasis on a cumulative causation of migration and on the inter-temporal dimension of migration.