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How the Carbon Cycle Helps Sustain Life on Earth

The words "Carbon Cycle" in white, under a white recycling glyph, above the image of a large tree in a green forest, representing how the Earth regulates the levels of carbon and greenhouse gasses in the atmosphere.
PublishedMarch 31, 2022
UpdatedMay 7, 2024
AuthorCory O'Brien HeadshotCory O'BrienSenior Director - Growth MarketingEditorRyan Barnett HeadshotRyan BarnettSVP, Policy & New Market Development
In this article
Carbon Cycle Definition
How Does the Carbon Cycle Work?
Why The Carbon Cycle Is Important
Human Impact On The Carbon Cycle
Carbon Recycling Helps Sustain Life On Earth

Carbon is an important part of human life. We’re primarily made of carbon, we eat carbon, and our economies, homes, and transportation are all built on carbon. Carbon moves throughout the planet in a process called the global carbon cycle, which is an essential part of our planet's overall health. However, as vital as carbon is to the continuation of our civilization, it also plays a huge role in one of the biggest threats facing our planet: global warming and climate change.

With this article, we’ll define the carbon cycle, explain how it works and how the Earth uses it to regulate the levels of greenhouse gasses in the atmosphere, and how human activities are unbalancing this global process.

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Carbon Cycle Definition

The carbon cycle is a natural process that moves carbon compounds throughout different deposits, or reservoirs, in the environment. (These reservoirs include the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere.) Carbon atoms naturally cycle through reservoirs, since all life on Earth uses carbon compounds for basic biological processes.

The carbon cycle occurs because Earth is a closed system, meaning that the total amount of carbon never changes. What does change is how much carbon resides in each of those reservoirs at any one time. While the largest deposits of carbon are stored inside rocks and sediment that exist below Earth's surface, the oceans and the atmosphere also hold carbon. From these sources, plants and animal life can draw on carbon to perform biological processes.

How Does the Carbon Cycle Work?

There are four natural steps that carbon can cycle through as it visits different reservoirs:

  1. Photosynthesis: Plants absorb carbon dioxide (CO2) in the atmosphere to produce the sugars they need to live, and this moves carbon from the air into plant matter.
  2. Decomposition: As deceased plants and animals decay, their carbon is released into the ground, which eventually solidifies into sediment stored beneath the surface.
  3. Respiration: Carbon is released into the atmosphere as living organisms breathe out, after extracting oxygen from the air, or after consuming plants.
  4. Combustion: Whether in volcanic eruptions or fossil fuel-based energy systems (basically turning dead organisms into fuel), the burning of fossil fuels and other carbon-based sediments releases energy, and carbon is returned to the atmosphere.

Those four steps of the carbon cycle work in tandem to move carbon throughout the environment. Just keep in mind that carbon doesn’t have to move through every step, since the carbon cycle is more of a system than a single process.

  • Photosynthesis draws carbon from the air and moves it into plant matter.
  • Respiration takes carbon within plant matter and moves it back into the atmosphere.
  • As organisms die, they decompose, and their carbon solidifies underground.
  • Combustion takes the underground carbon and releases it into the atmosphere, ready to be photosynthesized.

To help explain this process in more detail, we put together this carbon cycle diagram:

A diagram of how the Carbon Cycle works, including the steps of Photosynthesis, Decomposition, Respiration, and Combustion.

"Fast" Carbon Cycle

The fast cycle refers to the carbon cycle steps through which carbon can quickly cycle through the environment, and can be measured in a lifespan. Photosynthesis and respiration are the two steps associated with the fast cycle. This carbon is being processed through the food chain, with plants as the driving force.

Because of the swift nature of biological processes, the compounds are rapidly moved between plant matter, animals, and the atmosphere. Very little carbon is moved during any given spin through the fast cycle, but due to the speed of the process, the overall amount processed each year is greater than in the slow cycle.

"Slow" Carbon Cycle

The exchange of carbon compounds between the atmosphere and Earth (where it is stored in the ocean, rocks, and soil) is called the slow carbon cycle, and it can take millions of years. This process mainly involves the decomposition and combustion parts of the carbon cycle steps.

  • Natural processes within the Earth, like tectonics and internal chemical reactions, contribute most to slow cycling.
  • Carbonic acid within rain introduces compounds into the soil and oceans, where it begins to form into rocks that can store carbon.
  • Merging of decaying organic material from the fast cycle as it moves underground over a long time frame is also a factor.

While a single trip moves more carbon than its speedy sibling, the slow cycle is so gradual that it processes less carbon per year than the fast cycle.

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Why The Carbon Cycle Is Important

The most common carbon compound in the carbon cycle is carbon dioxide, a greenhouse gas. Greenhouse gasses are heavy enough to linger in the atmosphere and trap the excess heat energy that normally would radiate out into space. As more greenhouse gasses accumulate in the atmosphere, more energy is trapped.

Having some greenhouse gasses is crucial to keeping our planet at a habitable temperature. Without a warm atmosphere, Earth would be far too cold for life to thrive. However, the accumulation of too many greenhouse gasses can lead to global warming. This causes overall temperatures to rise, and extreme weather events to occur.

The natural carbon cycle keeps carbon atoms in the atmosphere regulated enough to avoid global warming. Human intervention, however, can disrupt this natural cycle.

Human Impact On The Carbon Cycle

Human actions have led to far higher carbon levels in the atmosphere than ever previously recorded. Using fossil fuels for energy and fuel is one of the biggest reasons so much carbon dioxide is now in the atmosphere.

While the carbon cycle can remove some of that carbon dioxide, it can only remove so much carbon from the atmosphere at a time. When we release too much, a buildup of greenhouse gasses occurs, which leads to global warming, extreme weather events, and other ecological and environmental crises.

Some examples of ways humans are creating greenhouse gases and overwhelming the carbon cycle include:

  • Cutting down forests for development greatly reduces how much photosynthesis occurs, and eliminates a carbon reservoir.
  • The agricultural sector uses heavy machinery that releases a large amount of carbon dioxide from the combustion process, while also clearing land in large quantities.
  • Gasoline- and diesel-powered cars emit carbon dioxide in their exhaust while being operated.
  • Because of our growing global market, international shipping uses huge amounts of fossil fuels to power ships, planes, and trucks.
  • Fossil fuel-based home heating systems, energy grids, and appliances are very common.
  • The textile and fashion industries produce a huge amount of waste, and the creation of certain fabrics can lead to high amounts of carbon emissions.

Carbon Recycling Helps Sustain Life On Earth

A properly functioning carbon cycle is crucial to maintaining a healthy planet and healthy life for everyone that inhabits it. The Earth must have a way to regularly distribute carbon throughout our environment to preserve the balance between plant, animal, and insect life. However, human activities have altered the cycle, funneling millions of pounds of excess carbon compounds into the atmosphere, especially in the form of carbon dioxide, a greenhouse gas.

The good news is that you can take steps to lower your carbon footprint. By making more environmentally-conscious decisions, you can reduce your contribution to growing emissions.

One of the best ways to lower your impact on the carbon cycle is to install solar panels on your home. By using renewable energy instead of fossil fuels, you can help slow global warming, and you could even lower your monthly energy bills in the process. Palmetto can help you take the first steps towards the installation of a solar power system on your home, so check out our Free Solar Design and Savings Estimate tool to get started today!

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About the AuthorCory O'Brien HeadshotCory O'BrienSenior Director - Growth Marketing

Cory brings over 8 years of solar expertise to Palmetto, and enjoys sharing that knowledge with others looking to improve their carbon footprint. A dog lover residing in Asheville, NC with his wife, Cory graduated from UCSB. If you run into him, ask him about the company he founded to rate and review beer!

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