Do Earth’s life support systems have a point of no return? A few years ago, Johan Rockström, executive director of the Stockholm Environment Institute, head of the Stockholm Resilience Centre and professor at Stockholm University, led an international team in defining “planetary boundaries” — a “safe operating space” within which changes in nine planetary systems (stratospheric ozone depletion, nitrogen/phosphorus cycle change, global freshwater use, land use change, biodiversity loss, atmospheric aerosol loading, chemical pollution, climate change and ocean acidification) must remain to avoid the risk of setting off a cascade of irreversible change.

According to the team, three of those — biodiversity, nitrogen inputs and climate change — already have been exceeded.

This interview originally appeared in the Winter 2012 issue of Momentum magazine, Ensia’s predecessor.