Prior to 1970 agriculture was the biggest contributor to atmospheric CO2.  (After 1970 the internal combustion engine took top spot!)  Land clearing, plowing, and summer fallowing actually release CO2 into the air - not to mention all those fossil fuel inputs like fertilizers and fuel!             But agriculture has changed!  Some annual crops can now sequester long-term up to 450 kg of soil carbon per hectare per year.  All crops remove CO2 via photosynthesis every day and convert it to carbon as they grow in size.  Photosynthesis is the most efficient CO2 pump on earth!           When you think about it, every square foot of arable land on earth is managed by someone - usually a farmer!  And the tons of CO2 photosynthesized on each acre when multiplied by the huge number of acres in the agricultural "solar panel" has a major impact on Global Warming.  For example, if a farmer grows a 1.5 ton per acre crop above ground and another 1.5 ton per acre of root mass below ground, at a carbon content of 45% he has just grown 1.35 tons of carbon per acre (3 x 0.45).  That acre of crop had to take 3.67 times as much CO2 out of the atmosphere to convert it to carbon - for a total of 4.95 tons of CO2 removed!  And that's just one acre!  Now, click again under the "Consumers" link above to read about the amazing connection between that acre of crop and your CO2 emissions!