Taking Population Seriously in the IPAT Equation: Ethical and Political Implications of Planetary Boundaries

This chapter focuses on the impact of demographic changes on the planetary boundaries of the climate system and biosphere integrity. Without neglecting the other major causes of climate change and biodiversity loss, such as economic growth, it investigates an essential but relatively marginalized aspect of the problem. It develops a normative approach that evaluates population policies and examines which policies can be justified in our context of planetary boundaries transgression, understanding population policies as government policies that influence fertility rates, such as educational policies, contraceptive availability, and taxes. The first section sets the framework for the analysis by explaining the contribution of the demographic factor to climate change and biodiversity loss. The second section critically examines an influential way of discussing population growth in the climate ethics literature: using the IPAT equation (Environmental impact = Population × Affluence × Technology) to over-emphasize the importance of “T” and downplay the role of “P.” The third section explores and evaluates population policies and proposes possible justifications for certain positive and negative incentive measures. The final section considers objections commonly made against these incentive policies.