What is the carbon cycle?

Blog Post by Ellie Shaw 18 August 2015

What’s carbon?

Carbon is an element that’s abundant across the entire world. It's present in all living things, is a major component of many minerals (it’s what diamonds are made of!) and is found in oceans, soils, rocks, oceans, lakes and rivers; pretty much everywhere actually. It’s found in solid, liquid and gas states, can be dissolved in water, and is also found in the atmosphere as the gas you’ll have heard a lot about, carbon dioxide (CO2), which is a compound.

What’s the carbon cycle?

The total amount of carbon in our world is fixed. We can’t make more and we can’t simply get rid of it. It's continuously cycled through organisms, the atmosphere, water and earth and is one of many important biogeochemical cycles (‘bio’ for the living organisms, ‘geo’ for the water, rocks and soils, and ‘chemical’ for the change from one matter to another) like the nitrogen cycle and the water cycle.

Green plants take carbon from the atmosphere which is in the form of carbon dioxide and turn it into glucose, which is a sugar. Plants can then use the glucose to make molecules like cellulose which makes up wood, and protein and oils in their leaves.

Next, animals come along and eat the green plants, digesting the plants and turning them into carbohydrates, fats and proteins to provide the animal with energy. The carbon is then returned to the atmosphere in the form of carbon dioxide through a process of cellular respiration, the process which gives the plants and animals energy and releases waste products. Carbon dioxide is also released back to the atmosphere when plant and animal matter decays.

This diagram shows a basic carbon cycle:

Carbon Cycle

Source: http://eschooltoday.com/ecosystems/the-carbon-cycle.html

So, what’s the problem?

As I said, there’s a fixed amount of carbon available and all of it is somewhere in the cycle. The problem comes when too much of it ends up in the atmosphere as carbon dioxide.  

You’ll notice on the diagram that ‘combustion gives off CO2’ is included. Human activities have interfered with the carbon cycle, releasing a lot of extra carbon dioxide into the atmosphere through the combustion of fuels including wood, coal, petroleum and natural gas. We’re also removing vast areas of forest and vegetation, meaning there are less plants to use and store carbon.

Carbon dioxide is a greenhouse gas. Greenhouse gases help keep our planet warm by trapping some of the sun’s rays, which means we are able to live on it! However, it’s all the increased carbon dioxide (along with some other gases) that increases this ‘greenhouse effect’, rising the average global temperature and leading to climate change.

Want to know more about the effects of climate change? Take a look at our other blogs on the subject!


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