Ecotones, such as advancing treelines, have been examined as complex self-organizing systems. Frontiers of human settlement may share some of their spatial characteristics, because they too include feedbacks between spatial pattern and process. Advancing frontiers of three study areas in the Amazonian region of Ecuador are analyzed with the aid of Landsat imagery to detect change. Power-law distributions of advancing deforestation are found, which are indicative of possible complexity. Alternative approaches in self-organized complexity, including self-organized percolation and the inverse-cascade model, and an approach to complexity involving optimization?highly optimized tolerance?are considered. Some combination of these, based on their common ancestry in percolation theory, might provide insights into population ? environment interaction at settlement frontiers.