"Not only is carbon dioxide's total greenhouse effect puny, mankind's contribution to it is minuscule. The overwhelming majority (97%) of carbon dioxide in the earth's atmosphere comes from nature, not from man. Volcanoes, swamps, rice paddies, fallen leaves, and even insects and bacteria produce carbon dioxide, as well as methane. According to the journal Science (Nov. 5, 1982), termites alone emit ten times more carbon dioxide than all the factories and automobiles in the world. Natural wetlands emit more greenhouse gases than all human activities combined. (If greenhouse warming is such a problem, why are we trying to save all the wetlands?) Geothermal activity in Yellowstone National Park emits ten times the carbon dioxide of a midsized coal-burning power plant, and volcanoes emit hundreds of times more. In fact, our atmosphere's composition is primarily the result of volcanic activity. There are about 100 active volcanoes today, mostly in remote locations, and we're living in a period of relatively low volcanic activity. There have been times when volcanic activity was ten times greater than in modern times. But by far the largest source of carbon dioxide emissions is the equatorial Pacific Ocean. It produces 72% of the earth's emissions of carbon dioxide, and the rest of the Pacific, the Atlantic, the Indian Ocean, and the other oceans also contribute. The human contribution is overshadowed by these far larger sources of carbon dioxide."
http://ilovecarbondioxide.com/2009/04/termites-emit-ten-times-more-co2-than.html