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NCAR
Biogeochemical Cycles
There are a few types of atoms that can be a part of a plant one day, an animal the next day, and then travel downstream as a part of a river’s water the following day. These atoms are found in living things like plants and animals. They are also found in non-living things like water, air, and rocks. The same atoms are recycled over and over in different parts of the Earth.
All of the atoms that are building blocks of living things are a part of these cycles. The most common of these are carbon and nitrogen. Find out more about how carbon and nitrogen move around the Earth!
Tiny atoms of carbon and nitrogen have no legs to walk, no bicycles, cars, or airplanes. Yet they can travel around the world. So, how do these little things move around the planet? Here’s an example: An atom of carbon is absorbed from the air into sea water. There, it is used by little floating plankton as they get the nutrition they need using the Sun’s energy to make food. This little carbon atom might become part of the plankton’s skeleton, or a part of the skeleton of a fish who eats it. Then it may become part of a sedimentary rock when the living things die and their bones are left behind. Carbon that is a part of rocks and fossil fuels like oil, coal, and natural gas may be held away from the rest of the carbon cycle for a long time. When fossil fuels are burned, carbon that had been underground is sent into the air as carbon dioxide, a greenhouse gas.
Recently, people have been causing these cycles to change (see links below). When we cut down forests, make more factories, and drive more cars that burn fossil fuels, the way that carbon and nitrogen move around the Earth changes. These changes add more greenhouse gases in our atmosphere and this causes more global warming.
