Carbon is one of the basic chemical building blocks of life. When carbon is united with oxygen it forms carbon dioxide or CO2. Plants and trees absorb CO2 for their biomass and then convert it to oxygen through photosynthesis. This process is known as the 'Carbon Cycle' and without it life on earth could not exist.
As trees and forests grow, they absorb CO2 from the atmosphere, acting as natural 'carbon sinks'. Some CO2 is also dissolved in the ocean. Other amounts are trapped in plant and animal biomass, and over thousands of years may become petroleum or coal.
