Traditional approach to the study of society-nature interactions based on reductionism and linear causality is no longer fully capable of explaining complex dynamics of integrated socio-economic and natural systems. For this reason demands for complexity theory is growing. Understanding interactions between society and nature, human and their environment must come from the examination of how the two systems operate together, and not from examination of those systems themselves in isolation. Since our geographical community is not familiar enough with complexity theory, first part of article is devoted to outlining shift from reductionism to holism and complexity theory. In the second part, features of complex systems as it is human (society)-environment system are discussed. .