<P> Current agricultural practices lead to carbon loss from soils . It has been suggested that improved farming practices could return the soils to being a carbon sink . Present worldwide practises of overgrazing are substantially reducing many grasslands' performance as carbon sinks . The Rodale Institute says that regenerative agriculture, if practiced on the planet's 3.6 billion tillable acres, could sequester up to 40% of current CO emissions . They claim that agricultural carbon sequestration has the potential to mitigate global warming . When using biologically based regenerative practices, this dramatic benefit can be accomplished with no decrease in yields or farmer profits . Organically managed soils can convert carbon dioxide from a greenhouse gas into a food - producing asset . </P> <P> In 2006, U.S. carbon dioxide emissions, largely from fossil fuel combustion, were estimated at nearly 6.5 billion tons . If a 2,000 (lb / ac) / year sequestration rate was achieved on all 434,000,000 acres (1,760,000 km) of cropland in the United States, nearly 1.6 billion tons of carbon dioxide would be sequestered per year, mitigating close to one quarter of the country's total fossil fuel emissions . </P> <P> Presently, oceans are CO sinks, and represent the largest active carbon sink on Earth, absorbing more than a quarter of the carbon dioxide that humans put into the air . The solubility pump is the primary mechanism responsible for the CO2 absorption by the oceans . </P> <P> The biological pump plays a negligible role, because of the limitation to pump by ambient light and nutrients required by the phytoplankton that ultimately drive it . Total inorganic carbon is not believed to limit primary production in the oceans, so its increasing availability in the ocean does not directly affect production (the situation on land is different, since enhanced atmospheric levels of CO essentially "fertilize" land plant growth to some threshold). However, ocean acidification by invading anthropogenic CO may affect the biological pump by negatively impacting calcifying organisms such as coccolithophores, foraminiferans and pteropods . Climate change may also affect the biological pump in the future by warming and stratifying the surface ocean, thus reducing the supply of limiting nutrients to surface waters . </P>

Oceans are a global sink for carbon dioxide