With climate change placing increasing pressure on environmental resources, it is now being viewed as a threat to national security.
History is littered with lessons from once-budding civilizations that crashed from their peak of prosperity. From the Anasazi of the southwestern United States to the Mayans of Mesoamerica1 and the ancient dynasties of eastern China2, environmental change has sounded the death knell throughout time for once-thriving civilizations already stressed by factors including high population growth, overexploitation of resources and excessive reliance on external trade. In many cases, severe drought or extreme cold has been enough to push societies to the brink of civil unrest, mass migration and warfare.
Meta note: Although I check out Nature.com every now and then (continuously with RSS, of course) Dr. Saleem H. Ali got to it first and indirectly notified me by posting it to his blog at Newsvine.com which I also subscribe to. Web 2.0 galore.