“...our analysis is informed by sociological and ecological theory and assesses the effects of a variety of factors on the “ecological footprints” of societies in a rigorous manner.”

I suspect that our paper is highly cited because it addresses one of the most important topics of the 21st century: the human factors that drive environmental degradation. Furthermore, our analysis is informed by sociological and ecological theory and assesses the effects of a variety of factors on the "ecological footprints" of societies in a rigorous manner.

We do not report a singularly new discovery, but, rather, refine existing theories by more precisely assessing how demographic, economic, and other forces influence the scale of human pressure on ecosystems. We do use a new statistical approach, which may have broad applicability, to assessing how human factors influence the environment. This approach was originally developed by my coauthors, Eugene Rosa and Thomas Dietz, and is based on an ecological model (I=PAT) that has served as a basis for environmental debates since the 1970s. We also analyze a new indicator of the impact of societies on the environment, the "ecological footprint"—originally developed by William Rees and Mathis Wackernagel at the University of British Columbia—which previously had not been examined in a similarly rigorous manner.

Our main finding is that nations’ ecological footprints are largely determined by the size of their populations and their level of material affluence (measured as per capita GDP). In particular, national ecological footprints are roughly proportional to population size, all else being equal, and, contrary to the claims of many neoclassical economists and modernization theorists, the ecological footprint rises steadily with economic development, showing no sign of leveling off or declining in the wealthiest nations. These results suggest that we are unlikely to obtain ecological sustainability by continuing to pursue endless economic growth and ignoring population growth, while hoping for a technological fix to solve our problems.

For a long time, I have been interested in understanding why human societies degrade the natural environment and also in finding ways to develop a sustainable society. Hence, I pursued an education in the environmental sciences and sociology. As a graduate student at Washington State University (1998-2002), I began working with Eugene Rosa, who served as my dissertation advisor, mentor, and collaborator. In the early 1990s Rosa had begun working with Thomas Dietz, now at Michigan State University, to develop ways to scientifically engage questions about human-environment interactions. I was invited to join the research program they established, and this paper, along with several others, are the product of that collaboration.