The carbon cycles and mankind


Besides the biological carbon cycle there is a slow geological carbon cycle that has a cycle time of several million years. It depends on two things: on a geologically active Earth and the presence of liquid water. Through the geological dynamics of the earth organic sediments and limestone sinks to great depths. The heat releases CO2. Through volcanoes and cracks in the rock it goes back into the atmosphere.


CO2 is taken up via photosynthesis by green plants on the continents or phytoplankton in the ocean. On land carbon is transferred to soils. Herbivores eat the plants, and carnivores eat the herbivores. Animals, but also plants generate CO2 through respiration. The plants and animals die and are decomposed by microorganisms with the ultimate production of CO2. The biocycle is also termed “the fast carbon cycle” since the processes occur in a time frame from several days to several tens of thousands of years. This is fast compared to the time scale of the geocycle.

Human influences

Since the Industrial Revolution man has meddled in the slow as well as in the fast carbon cycle. He quarries limestone and makes cement, setting CO2 free. He takes out crude oil, natural gas and anthracite or lignite coal and burns these. He also clears forests and with that hinders the binding of CO2. Thus in a few days, resources are used up, whose production lasted millions of years.