By Diagram adapted from U.S. DOE, Biological and Environmental Research Information System. - http://earthobservatory.nasa.gov/Features/CarbonCycle/, Public Domain, Link
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As mentioned, carbon is an essential part of organic life on Earth. Scientists specialized in matter throughout the universe tend to think that this is case not only on our planet, but across galaxies and beyond. We've found that carbon is abundant not only on Earth, but in all manner of space-faring objects. Quantity isn't really a defining factor in organic life, though. I mean, we don't have hydrogen- and oxygen-based life forms despite their abundance (though those do play important factors in life on Earth).
What makes us believe carbon is so important to organic life is not in quantity of the element, but quality of it. Specifically, its ability to bond with other elements. Furthermore, to bond and remain stable. Without getting into the chemical nitty-gritty, the way carbon's valence (outer) electrons are situated makes it eager to bond with other elements. This includes other carbon molecules, all without sacrificing the stability of the resulting chain of matter. So, it isn't so much that carbon has a "living" quality to it, but its ability to bond in seemingly countless ways allows for any number of permutations to potentially form organic life. |
Carbon is uniquely stable while supporting bonds with many other elements, making it a prime candidate in structuring living organisms |
Carbon is abundant and it is strongly thought that all life in the universe depends on it |
Where is Carbon?Okay, we now know that carbon is pretty important. Organic life needs its ability to form strong, stable bonds in order to survive. We also said it's abundant, so where is it on Earth? The short answer is, well...everywhere!
Carbon, like our other cycles, has a concept of reservoirs, or places where carbon is stored and moved between. We also have the concept of "sinks" or places where carbon is pulled from the cycle as readily available for a time. Primarily, though, carbon is moving between various reservoirs. These being the hydrosphere (water), atmosphere (the air around us), biosphere (the living parts of the planet), and geosphere (the inorganic parts of the planet). |
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Most of that probably sounds pretty stationary, and, to be fair, this cycle moves a lot slower than something like the water cycle. With the exception of the atmosphere and the surface carbon in the oceans, carbon can stay in one spot for years, decades, or centuries. The planet was built to handle carbon as a slow cycle, but it does move!
As mentioned, the oceans like to trade carbon with the atmosphere almost constantly. There is a certain equilibrium that the hydrosphere and atmosphere work toward, but as the planet changes in both how fast carbon is moving and where the most carbon is stored, this balance fluctuates. Nonetheless, carbon is moving in this interaction. From the atmosphere, our good friend plants like to pull carbon dioxide out of the air in into themselves via photosynthesis. This process allows the plant to grow. For our herbaceous examples, this carbon is either pulled into the Earth after a plant has gone through its life, or is eaten by other life forms. |
Carbon is housed in the Earth's water, air, land, and all living things. |
Getting carbon our of the geosphere is a normally massive task. |
The slowest of the movement comes in the deep marine and geosphere reservoirs. Getting into the geosphere is a generally of a process of time, carbon deposits, and usually some help from water. Carbon deposits will, over time, cement themselves to existing rock structures. There are also marine creatures that can pull calcium carbonate from ocean water to form their skeletons and shells which, after a time, will become carbon deposits of their own. Getting out of the geosphere is a bit tougher, but comes down to combustion, such that solid carbon forms are released into the air as carbon dioxide. Carbon sediment can find its way into volcanoes via subduction in the deepest marine ecosystems...or...
Enter the HumanHumans can help move it faster! Since the industrial revolution, humans have discovered a way to harness energy from carbon that they have found around the Earth. This way is, of course, combustion, which is a means to take carbon locked in the geosphere and release it into the atmosphere as carbon dioxide. Our discovery, however, has led us to do two things very quickly. First, we find long term carbon stores in the soil and geosphere and burn them, and second, chop down a great deal of one of Earth's best carbon sequesters: forests.
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Earth is what is called a closed system. Elements on our planet rarely leave the planet. The amount of carbon on Earth is not changing, but where it is stored is changing dramatically. This change is causing the planet's average temperature to rise, altering the local climates of ecosystems and causing balances to shift. For example, the ocean surface's equilibrium will start to shift to push more carbon into the atmosphere as the ocean's acidity rises. The climbing temperature in conjunction with other human practices have shown us that acidic oceans are bad for both life in the ocean and its capability to hold as much carbon as it does today. Climbing temperatures also heavily impact our arctic regions, which are now unintentionally exposing carbon sinks embedded in permafrost, pushing more carbon into the atmosphere that we're not utilizing for any benefit.
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Humans have altered both the amount of carbon pushed into the atmosphere while removing forests to pull carbon out of the air impacting the balance of Earth's systems |
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