In September 2009, the U.S. National Science Foundation's (NSF) Advisory Committee for Environmental Research and Education (AC-ERE) released "Transitions and Tipping Points in Complex Environmental Systems," a report that advocates sweeping change in the way environmental research and education are sponsored and conducted. The conviction of the committee that physical and life scientists, engineers, educators, and social scientists must work collaboratively to understand the dynamics of complex environmental systems should resonate with AGU's membership. A major theme of the AC-ERE report is that scientists need to understand environmental systems that, partly owing to human activity, may be approaching thresholds for irreversible change. This theme echoes sentiments expressed in the geosciences community, such as by Rockstrm et al. , who estimate the magnitudes of thresholds for irreversible changes in nine key Earth subsystems and focus on how human activities have driven systems closeror even pastsome thresholds. The AC-ERE report argues that understanding natural systems will require integrated research among geoscientists, social scientists, ecologists, and others.