Abstract

The complex dynamics of the human–environment relationship—from the deep past through the present into the future—provide a unique perspective in Earth system analysis. This chapter focuses on the last century, accounting for discontinuities, nonlinearities, thresholds, feedbacks, and lag effects in the human–environment relationship. Environmental responses to human activities, which include changes in knowledge, science and technology as well as feedbacks through population dynamics, energy, institutions, and political economies, are presented as a linked human–environment system. In this system it is clear that a tension exists between the momentum of past changes and the potential for future deceleration of rapid changes, particularly since the 1950s. The strength of the links and associated feedbacks between the human and environmental components (positive and negative) operate over variable time and space domains. Indicators of the significant decadal processes are presented to aid understanding of the rapid changes in the human–environment system since the 1950s. It is suggested that by accounting for the discontinuities, thresholds, and surprises inherent in a complex systems approach, insight into the mechanisms of the human–environment relationship can be gained to allow testable hypotheses for the future of the Earth system.