Human population as a dynamic factor in environmental degradation

The environmental consequences of increasing human population size are dynamic and nonlinear, not passive and linear. The role of feedbacks, thresholds, and synergies in the interaction of population size and the environment are reviewed here, with examples drawn from climate change, acid deposition, land use, soil degradation, and other global and regional environmental issues. The widely-assumed notion that environmental degradation grows in proportion to population size, assuming fixed per capita consumption and fixed modes of production, is shown to be overly optimistic. In particular, feedbacks, thresholds, and synergies generally amplify risk, causing degradation to grow disproportionally faster than growth in population size.