The carbon cycle is defined by the fundamental process of life, death, and rebirth. Carbon makes up about 23% of our elemental composition by mass. Almost a quarter of the human body is made of carbon. It is the building block for all organic molecules in the body. Glucose, the basis of sugar that sustains cell function, is a carbon compound. Every living thing, and most nonliving things are composed of carbon. It is quite literally everywhere.
But somehow we only hear about it when it’s a problem. The blame is often put on carbon for changing our planet. We forget that we need carbon. Like it or not, it’s what literally gives us and the world around us a physical form. It has cycled naturally through the environment for as long as our planet has existed.
There are two ways in which this happens. The first is the biological, or fast, cycle. This is what you might expect when thinking about carbon’s nutrient flow. Plants photosynthesize. They turn carbon dioxide and water into glucose sugars and oxygen by harnessing the sun’s energy.
Respiration is the same process in the opposite direction. At night, trees take oxygen and glucose they produced during the day and turn it back into carbon dioxide, water, and energy. The breaking of chemical bonds in glucose results in the energy that plants can use for all cellular processes.
While a tree holds on to the glucose it collects in its wood, the tree is a carbon storage. Ideally, it takes in and stores more carbon than it is releasing into the open environment. Photosynthesis should be greater than respiration in a stable environment. This is part of the reason healthy forests are so important.
These same processes occur in most grasses and shrubs. They store carbon in their leaves, branches, and berries. Rabbits and deer eat the berries and use the carbon-based sugars within them to fuel their own growth. A fox eats the rabbit, a wolf eats the deer, and the process continues up the food chain. At some point everything dies. The tree, the grass, the rabbit and the wolf return back to the soil, fueling the next generation of life from the ground up and providing the resources for life to continue in a cyclical and reciprocal manner.
The second cycle is the geological, or slow, carbon cycle. This movement of carbon is defined by the global natural system. When it comes to a cycle you can start anywhere as, ultimately, it should lead you back to the beginning. But for ease of explanation let’s start with carbon dioxide.
Atmospheric carbon dioxide is not inherently bad. We need it floating around up there if we don’t want to freeze the entire planet over. Carbon dioxide is a greenhouse gas, meaning it traps solar radiation in our atmosphere, keeping us warm. Otherwise, as our geological history shows, the Earth would be a giant snowball.
As carbon dioxide goes on its merry way in the atmosphere it comes into contact with water vapor and clouds. Carbon dioxide reacts and combines with water to create carbonic acid. Perhaps surprisingly, rainwater is naturally a bit acidic due to this reaction. The presence of this acidity is critical to the interaction between rainwater and limestone rock. Limestone rock is calcium based and very fragile and easily eroded. When the slightly acidic rain falls on limestone, a process called weathering occurs. Particles of the calcium rich limestone break off the rock and wash downstream with the rain along with the carbonic acid.
Most of this calcium-carbon enriched water will end up spilling out into the ocean. Once in the ocean, the tiny organisms that sustain most life in the ocean – phytoplankton – and many others use calcium carbonate to build their shells and skeletons. As these organisms live and die, they trap immense amounts of carbon in their bodies and store it at the bottom of the ocean. This is one of the most critical carbon stores in the cycle. There are eons worth of carbon stored on the bottom of the ocean. The settling of these little critters on the ocean floor is commonly called ‘marine snow’. An estimated 50% of carbon that enters the ocean ends up as marine snow.
These little organisms add up in layers-deep sediments at the bottom of the ocean. Over hundreds of thousands of years, tectonic plates inch the layers of sediment across the globe. At some point these tectonic plates slide underneath each other. The ground deep, deep beneath our feet heats up with the friction of these plates rubbing against each other. Eventually volcanoes erupt. The carbon stored in the fossils of those organisms long ago is melted and released back into the atmosphere as carbon dioxide. And the cycle begins again.
This is certainly a simplified explanation of the way these systems work. There are many more factors that play roles in how carbon moves through our environment, not all of them known. But I think the most important takeaway is that carbon is critical to every aspect of our survival and is worth a so-called “appreciation post”.
The reason we find ourselves in the predicament of too much atmospheric carbon is that we have redirected this cycle. The compacted layers of sediment of marine organisms are what we call fossil fuels. This massive carbon storage that holds the element inactive for thousands of years is routinely being pulled out of hibernation and released back into the atmosphere when it is burned in our power plants and cars. The longest period of the geological carbon cycle is being sped up and the rest of the system finds itself in back order, unable to keep up with the demand to pull carbon dioxide out of the atmosphere.
There is so much that is not reported on when it comes to climate change. So many good things that are swept under the rug in favor of sensationalism and alarmism. We are actively moving towards a more sustainable and environmentally conscious world. The race to switch to renewable energies is occurring much faster than anyone ever expected. In so many circumstances renewables are cheaper than fossil fuels, triggering market incentives for the switch. Public interest and awareness is growing by leaps and bounds. Positive change is actively happening all around us.
It’s very easy to focus on the negative. We want it to happen faster, it could always be faster, but the tendency is to fixate on what we should be doing, what mistakes we’ve made, only bogs people down. What if we looked at it from the other direction? Look at what we have the opportunity to do, the change that we are poised to make. It is a solvable problem. The solutions, the technology are out there and are becoming more accessible by the day.