The Carbon Cycle, Fossil Fuels, and Deforestation
Introduction
All things, living and non-living, consist of chemical elements. In this essay, we will be focusing on the chemical element with six protons: Carbon. This element plays a primary role in our climate by combining with oxygen to make carbon dioxide, a greenhouse gas.
Greenhouse effect — the trapping of the sun's warmth in a planet's lower atmosphere. The sun heats (via radiation) Earth’s surface during the day. At night, the surfaces cool and release the heat (radiation) into the air, where it is absorbed by greenhouse gases.
Greenhouse gas — a gas that absorbing infrared radiation, contributing to the greenhouse effect. Examples include carbon dioxide, water vapor, and methane.
Radiation — the emission or transmission of energy in the form of waves or particles through space or a material medium
Greenhouse gases trap the sun’s heat, and therefore dictate our temperature. If there is too much greenhouse gas in the atmosphere, the temperature is too hot. If there isn’t enough, the temperature is too cold.
Carbon continually cycles from one part of the world to another. The simplest part of this cycle is photosynthesis, so let's start there. During photosynthesis, plants (1) take in carbon dioxide from the atmosphere, (2) separate the carbon and oxygen, (3) keep the carbon for themselves, and (4) release the oxygen into the atmosphere. It's this process that makes plants a "carbon sink." The plants use carbon they've stored as energy.
Carbon dioxide — Colorless and non-flammable gas made up of one carbon atom and two oxygen atoms.
Carbon sink — any reservoir, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby lowers the concentration of carbon dioxide from the atmosphere
Animals (including us) reverse this cycle each time they (or we) breathe. During respiration, the animal (1) takes in oxygen, (2) adds carbon stored in its body, and (3) releases carbon dioxide. This process makes animals a “carbon source.” Below is an image representation of this small part of the carbon cycle.
Carbon source — any natural or artificial production site of carbon and/or any chemical compounds composed of carbon, such as carbon dioxide and methane.
Herbivores obtain the energy they need from carbon by eating plants (who store carbon from photosynthesis), and carnivores from eating other animals (who store carbon from eating plants or animals). Animal release this same carbon back into the air during respiration. This transfer adds a little more complexity to the carbon cycle, as shown in the image below.
Fossil Fuels
As I wrote earlier, all things, living and non-living, consist of chemical elements. Carbon is one of the most common of these chemical elements. So, in that same vein, almost all things are partially made up of and derive energy from carbon. When living things die, they fall back into the earth, which compresses them under immense pressure for a very long time. This process is called fossilization.
At some point, humanity figured out that when animals die, they maintain their carbon, and we can still derive energy from their fossils. That was a big realization. We harnessed this energy with the combustion of fossil fuels, such as petroleum oil, and used it to power our society through the industrial revolution and out of poverty. We went from horses to trains to cars and from candles to electrically powered lightbulbs.
Fossil fuels provide carbon-based energy through hydrocarbon combustion.
Hydrocarbon — a molecule that contains carbon and hydrogen. The primary constituent of fossil fuels.
Hydrocarbon combustion — the chemical reaction where a hydrocarbon reacts with oxygen to create carbon dioxide, water, and heat.
During hydrocarbon combustion, hydrocarbon reacts with molecular oxygen, producing carbon dioxide, water vapor, and heat. This process begins with the burning of the fuel.
Before our newfound ability to burn fossil fuels, our carbon cycle was in relative equilibrium. But, burning fossil fuels also releases carbon dioxide into the atmosphere, and the extra carbon dioxide from burning fossil fuels has broken our equilibrium.
The carbon dioxide arrow is drawn to get thicker as more and more carbon is pumped into our atmosphere from fossil fuel combustion. The arrow below shows the increase in carbon emissions from fossil fuel combustion since the 1950s.
The extra carbon has two effects. One, because carbon is a greenhouse gas, it traps the sun’s heat and increases the global temperature. Two, it puts an extra burden on our plant life to process this carbon. This is a major problem because, at the same time that we've been burning fossil fuels, we've also been cutting down forests at a rate that too fast for them to regrow. So, we're increasing our carbon output while eliminating much of the planet's ability to process it.
Deforestation
We’re not cutting down trees for no reason. We need their timber for paper and wood products, and forests often occupy land that would be ideal for farming. The process of removing trees to make the room for something other than a forest is called deforestation.
Deforestation — the process of removing trees to make room for something other than a forest. This includes agriculture and using timber for other purposes.
But, trees serve a purpose both in life and in death. Forests, as we’ve seen earlier, function as the primary filter for carbon dioxide. Water transpiration from trees also returns water to the atmosphere, allowing for more rainfall. Trees retain water in the soil and protect the land surface against landslides, soil erosion, and sediment runoff into streams. Citizens of developing countries also use forests as the primary place to hunt for food, gather fruits and nuts, and obtain plant-derived medicine.
Water transpiration — the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers.
Soil erosion — the deterioration and removal of the most fertile top layer of soil through water, wind, and tillage
Landslide — a song by Fleetwood Mac
Sediment runoff — the build-up of eroded soil particles that are transported in runoff from their site of origin and deposited in drainage systems, on other ground surfaces, or in bodies of water or wetlands.
Two other important notes: (1) When deforesters cut down trees, they also release much of the carbon stored in them into the atmosphere. In this sense, deforestation acts as a carbon source and deprives us of a carbon sink. (2) Forests are renewable. Trees can be cut down and replanted at a sustainable rate so that the Earth can maintain its forests permanently. We can have both wood products and carbon dioxide filtering. But, we must deforest at an appropriate rate, and humanity has been notoriously bad at using resources wisely.
In sum, forests provide many things we need for everyday life. We take value from trees and plant life while they’re alive and after we cut them down. But, we lost the value trees give us in life when we take the value they provide in death. For instance, a single tree cannot simultaneously provide wood for a home and filter carbon dioxide. But, forests are renewable. So, we can have a set amount of each if we behave appropriately.
Conclusion
With fossil fuels adding to the atmosphere’s carbon level and deforestation leaving us with less filtering capacity to process it, we break the carbon cycle on both ends. All this time, the greenhouse effect continues. As the rising level of carbon in our atmosphere traps more heat, our temperature continues to rise.
Sources
Jared Diamond’s Collapse
Energy Education’s explanation of Carbon
Energy Education’s explanation of Hydrocarbon Combustion
EPA’s Greenhouse Gas Emissions Data
NASA Space Place’s video on the Greenhouse Effect
One Tree Planted YouTube channel
National Geographic’s Climate 101: Deforestation
The Economist’s video on the Carbon Cycle
EarthPen’s video on the Carbon Cycle
Khan Academy’s video on the Carbon Cycle
Nathaniel Manning’s TedEd Lesson on the Carbon Cycle
MooMooMath and Science’s video on the Carbon Cycle
