Those of us who became part of the wave of vegetarian life-style change, ca. 1970, understood that a meat-centered diet was unsustainable and that eventually many millions more would have a non-meat-centered diet thrust upon them by circumstances beyond their control. Those circumstances are coming to fruition today. Witness the upsurge in interactive prices of food and fuel. It is now clear to everyone that the two are intertwined and have planetary ramifications.
With huge increases in population--both here in the U.S. (the Pew Research Center projects that the U.S. will reach 438 million by 2050) and world-around (the U.N. projects 9.1 billion by 2050)--the food-and-energy nexus is now a life-and-death issue for several billion people and for the health of the Planet.
Also, with rapid and continuing globalization (the world acting as a single place), it seems to me that the world is increasingly OVER-DETERMINED (resulting from multiple and reinforcing causes) to the utmost degree. Our dietary and energy-use habits now have planetary impact. Buckminster Fuller, in his Operating Manual for Spaceship Earth, convinced many of us 38 years ago.
The concept of over-determinancy should persuade that each of us is sitting in the captain's chair. With our hands firmly on the controls, where will each of us guide the Ship?