Nutrient cycles. Chemical elements that make up a living being, such as carbon, oxygen, nitrogen, hydrogen, potassium, calcium, phosphorus, sulphur and many others, are transported between living organisms and non-living components of the planet.
These elements are essential for the structure and function of living organisms. Some will accumulate in them while they are alive and return to the soil and the atmosphere when they die. Drastic changes in the dynamics of these cycles produce pollution, eutrophication (surplus nutrient levels in wetlands) and ultimately global climate change.
Carbon is found in the atmosphere, biosphere, oceans and sediments. Plants take carbon dioxide from the atmosphere and convert it into carbohydrates and, in this form, a large part of global carbon is stored in forests and soil. In the sea, many organisms use carbon to form their external skeletons and shells. Carbon returns to the atmosphere through respiration of organisms, organic decomposition, combustion, and volcanic eruptions. The other chemicals have similar cycles.