Ecological Sustainability

247Mitigations of Human Impacts through Technology

forcing due to contrail cirrus remains the largest single radiative forcing

component associated with aviation.

Other, harder-to-quantify, diffuse sources of atmospheric CO

2

include

the natural decay of vegetation, burning of rainforests to make agricultural

land, animal respiration, and volcanoes. Some CO

2

sources are considered

“green,” that is, their combustion releases CO

2

that has recently been incor-

porated into their biomass (plants, trees, wood, leaves, etc.), or, in the case

of animals, their breathing releases CO

2

that came from them metabolizing

eaten plant food or from eaten meat from animals that ate plant food. Plants,

of course, incorporate atmospheric CO

2

into their ...