The Carbon Cycle

Hello!

Apologies for not posting earlier; I was trying to focus my blog down into an area of interest in terms of global environmental change and what could make a planet uninhabitable.

I've decided to focus on one particular area of the environment: the carbon cycle. I aim to explore the question: how are humans impacting the carbon cycle to affect the habitability of Earth? Astrophysicists Henning and Salama (1998) state the importance of carbon, particularly for evolution as it is the fourth's most abundant element in the universe and has the ability to form complex species. As such, carbon is a key element on Earth and can influence many different areas. I'll be exploring changes in the carbon cycle and the effects on both the environment and on humans.

This post is to give a brief introduction to the carbon cycle and its role as a major part of Earth's environment.

What is the carbon cycle?
Have a quick look at this Crash Course video that nicely introduces the carbon cycle (start at 1:02).

As Hank Green so eloquently put it, carbon is "the stuff of life, so the carbon cycle is a whole bunch of things living and dying, and in the process, swapping carbon". Below is a nice and simple graphic that displays the different carbon stores on Earth and the processes that lead to carbon being swapped between stores.

Some of the ones of particular note are carbon in vegetation, which humans are altering rapidly; as well as coal, oil and gas or carbon extracted and used as fossil fuels to emit carbon back into the atmosphere. This is heavily influenced by human activity, which leads me nicely on to my next question:

Why do changes in the carbon cycle matter?
I've briefly outlined what the carbon cycle is, but why does it really matter if it changes? Well, I personally see it as a matter of balance. As the diagram shows, carbon is stored and moves around in many areas, but if one store grows much larger relative to other stores, this throws the balance of carbon completely off and can have huge consequences. NASA's Earth Observatory website states that the balance of the carbon cycle acts "like a thermostat", helping keep Earth's temperature relatively stable.

In the history of Earth, variations in the carbon cycle have been a result of Earth's orbit, which changes the amount of energy Earth receives from the sun, and therefore the climate of the Earth. Glacial periods have slowed the carbon cycle and interglacial periods speed up the carbon cycle. However, in recent years (exact time debatable), humans have had a significant impact on the carbon cycle. Many scientists debate this new and unnatural epoch, named the Anthropocene, as the time period with which humans have wrenched Earth out of its natural cycles of warm and cold, and carbon is in the centre of this change. As humans change the carbon cycle, this has a ripple effect across the environment.

Hence, changes in the carbon cycle have widespread effects on different areas in the environment. For example, Schlesinger et al. (2000) have studied soil as a pool (or store/reservoir) of carbon and concluded that human activities, particularly cultivation, have reduced the pool of carbon in soils and transferred it to the atmosphere. This is likely to further exacerbate the greenhouse warming effect of carbon in the form of carbon dioxide in the atmosphere, with further consequences related to the rising temperature of the Earth.

While many changes in the environment could make Earth uninhabitable for humans and many species, I sincerely hope humans aren't changing the carbon cycle to this detrimental consequence and only time will tell if we are beyond the point of no return. I hope this brief introduction to the carbon cycle sets the context for its importance in the changing global environment and I'll be looking to explore further within specific aspects of the carbon cycle with how they are changing and what effects this might have.

Thanks for reading!