The Green Zone is an American-style biosphere. It is a completely enclosed self-contained system that makes its own water and air. It you left a McDonald's burger in the Green Zone for a year, it wouldn't decay. It would be perfectly preserved like a priceless ancient antiquities.

The biosphere is the part of the Earth, including air, land, surface rocks, and water, within which life occurs, and which biotic processes in turn alter or transform. From the broadest biophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere. This biosphere is postulated to have evolved, beginning through a process of biogenesis or biopoesis, at least some 3.5 billion years ago.

Biomass accounts for about 3.7 kg carbon per square meter of the earth's surface averaged over land and sea, making a total of about 1900 gigatonnes of carbon.