After seeing the results of my colleagues’ work at the end of the semester, interdisciplinary collaboration has new meaning for me. Although those of us taking NR&E 545 entered with a range of backgrounds from the natural, physical, and social sciences, none of us had previously been exposed to transition theory, or at least not in the manner in which it had been presented. The concepts of overshoot-and-collapse and "turnings" in time empowered us to view problems in a whole new light as well as united us with a common language. In other words, our independent paths of knowledge intersected with the concepts of population-environment dynamics, but then took off into different directions based on our interests and background. By starting on the same footing, connections and relationships were easier to define and understand.

The geographical areas presented in this monograph not only span the globe but also span the spectrum of political and economic infrastructures. However, the population dynamic is additionally affected by the social, environmental, and spatial characteristics of a region or country. The chapters by Kim and Scaff have an interesting connection to mine because of the communist governments that were (or are) in power. In a centrally-planned economy, particularly as practiced by the Soviet regime, it is theoretically possible to manipulate movement and migration within the country. Clearly in Vietnam, Eastern Germany and Russia, attempts were made to control where and how the population lived. In Russia, the government encouraged or forced people to move from European Russia to Siberia and in Vietnam, the government induced people to moved out of the densely-populated Red River Valley. The transition of the population out of the traditionally populated areas was very different in Russia and in Vietnam, however, due to two important aspects of transitions themselves. First, the vastly different sizes of the countries meant that the scale of the transitions were very different, and secondly, the nature of political power meant that the trajectory of the transitions were different.

Since the dissolution of the Soviet Union, migration within Russia is no longer regulated by the government but instead is driven by viable economic opportunities. The geography of the country in terms of the climate and physical infrastructure determine where the economic opportunities will be located. The chapter on the Sahel by Chaudhury presents an area of similar size and similar variations in climate, although opposite in the extremes. The desertification of the Sahel region is the outcome of continuous deforestation, which has precipitated population movement into coastal, urban areas for economic reasons. The population in the former East Germany is moving from the environmentally degraded regions into Berlin and West Germany for similar reasons.

The urbanization transition is characterized throughout the chapters, but perhaps, the chapter by Lo offers a glimpse at our future world. Sao Paolo is a manifestation of ultra-urbanization that is occurring throughout many parts of the world. In Brazil, urbanization has been accompanied by a huge population increase. The disparity between the rural and urban areas also promotes rural-urban migration. Although Russia is not experiencing a population increase, many cities that were created by the socialist government are declining because the current economic structure cannot sustain their existence. Hence, urban areas that can support a bigger population are attracting people from smaller urban areas.

At the heart of all the chapters, however, are the reasons and circumstances that have led to the current state of transition in each country or region. Past practices offers insights into future outcomes, which is the basis for the curve fitting of data. The chapter by England provides an interesting account of the history of violence in Burundi in order to understand the past and predict the future. This is the premise of The Fourth Turning, which challenges us to find connections between our present-day world and the not-so-near past.