Carbon sink vs. source
All living organisms contain carbon. Forests, soil, oceans, the atmosphere, and fossil fuels are important stores of carbon. CO2 in the atmosphere are called a carbon “sources”, while the processes that absorb CO2 are called carbon “sinks.” Carbon is constantly moving between these different stores in a cycle, either as “sinks” or “sources.” A sink is anything that that absorbs more carbon that it releases, while a carbon source emits more that it absorbs. The amount of carbon in the atmosphere at a given time depends on the balance that exists between the sink and sources. The system of sinks and sources is known as the carbon cycle.
Natural sources of CO2 include volcanoes, fire, respiration, decomposition, and digestion. Natural sinks for atmospheric CO2 include photosynthesis, forests, oceans and freshwater bodies, fossil fuels, and carbonate rocks. The cycling of carbon between the atmosphere, plants, and animals can take place in a relatively short time. Other parts of the cycle involving storage of carbon like underground minerals, may take millions of years to complete. Individual carbon atoms may cycle through plants and animals several times a year. Rain forests and oceans absorb more carbon dioxide than they emit. They absorb half the CO2 humans release into the atmosphere. When marine organisms or plants die the carbon they stored is removed from the atmosphere often for millions of years.
Human disruptions to the carbon cycle are impacting the maintenance of the concentration of atmospheric carbon. This is leading to an increase in the amount of carbon in the atmosphere as humans produce CO2 and methane faster than the natural sinks can absorb it. Human activities also contribute significantly to carbon sources. We are also interfering with natural carbon sinks. For instance, the cleaning of tropical rain forests for agriculture and logging represents a significant loss in the earth’s ability to absorb and store...