Meeting the challenges of the anthropocene: Towards a science of coupled human–biophysical systems

We have entered an unprecedented era with regard to the impact of human actions on the Earth’s biophysical systems. Humans have always acted in ways that affect their surroundings (Turner et al., 1990), but only recently have anthropogenic drivers become major factors at the planetary level (Steffen et al., 2004). We have appropriated half the planet’s land surface for human uses, eliminated 90 percent of the big fishes in the oceans, severely depleted the earth’s stratospheric ozone layer, and increased atmospheric concentrations of carbon dioxide by more than a third relative to pre-industrial levels. The impacts of human actions on biophysical systems have become so broad and deep that many observers now speak of humandominated ecosystems (Vitousek et al., 1997) and argue that we have entered a new planetary era best described as the Anthropocene (Crutzen and Stoermer, 2000). As the name suggests, the defining feature of this era is the emergence of human action as a critical force in a range of biophysical systems. One consequence of this development is that any attempt to explain or predict the behavior of large biophysical systems can no longer succeed without addressing human actions as a central concern. We also must recognize that biophysical forces exert a powerful influence on humans and their social systems. While advanced technologies and economic prosperity have cushioned affluent societies from many of the impacts of resource scarcity and environmental disturbances, we are far from immune. Much of the world’s population lives in extreme poverty and lacks access to the most basic necessities (e.g., safe drinking water and sanitation), leaving these communities highly vulnerable to changes in resource availability and biophysical threats. Even wealthy countries cannot escape the consequences of global environmental changes, such as rising sea levels, violent storms, and health hazards resulting from climate change (Diamond, 2005; Linden, 2006; Confalonieri and McMicael, 2006). Human and biophysical systems are coupled: human actions affect biophysical systems; biophysical forces affect human well-being, and humans respond in turn to these forces. As environmental problems of the Anthropocene