BiologyBoundaries for a Healthy PlanetScientists have set thresholds for key environmental processes that, if crossed, could threaten Earth's habitability. Ominously, three have already been exceededApril 1, 2010 — Jonathan Foley, Gretchen C. Daily, Robert Howarth, David A. Vaccari, Adele C. Morris, Eric F. Lambin, Scott C. Doney, Peter H. Gleick and David W. Fahey
