CARBON CYCLE

Well, while many people in their daily life may never think about how their actions affect the natural phenomena that regulates the temperature they enjoy though the daily increase of individual release of CO2 to the atmosphere, we environmentalist think about it all the time maybe more so because of research and studies but also because we are aware that it is the major driving force for world wide trending issues surrounding CLIMATE CHANGE.

CARBON CYCLE

Carbon is present in all living things and continuously moving among Earth’s lithosphere, hydrosphere, biosphere and the atmosphere in various forms for instance as carbon dioxide (CO2) in the atmosphere, sugar or carbohydrates (CnH2nOn) in living organisms and calcium carbonate (CaCO3) in rocks and minerals, the movement of this carbon among the Earth’s spheres is known as the carbon cycle.

Carbon Cycle

Adopted: http://www.visionlearning.com/en/library/Earth-Science/6/The-Carbon-Cycle/95

This illustrates how much carbon is stored in carbon sinks and how carbon moves among the Earth’s spheres.

The earth has a natural system of balancing CO2 in green plants that play a very significant role in, absorbing carbon dioxide and producing sugars that contain carbon referred to as photosynthesis and animals by eating plants to obtain the energy trapped during the process of photosynthesis, as the animals bodies break down the carbohydrates in the plant tissue, CO2 is released to the atmosphere a process called respiration, CO2 is also released when plants and animals decay.

Different paths of the carbon cycle recycle the element at varying rates. The slowest part of the cycle involves carbon that resides in sedimentary rocks, where most of the Earth’s carbon is stored. When in contact with water that is acidic (pH is low), carbon will dissolve from bed rock, under neutral conditions, and carbon will precipitate out as sediment such as calcium carbonate (limestone). This cycling between solution and precipitation is the background against which more rapid parts of the cycle occur.

Figure 10: Atmosphere Carbon Store

Adopted: http://www.carbonequity.org/types-of-global-co2-emissions-caused-by-human-activity/

Carbon is constantly cycling from the air into plants and soil, and back into the air. Life is built on the conversion of carbon dioxide into the carbon-based organic compounds of living organisms.

CARBON CYCLE – SOURCES AND SINKS

The carbon cycle illustrates the central importance of carbon as it is stored on our planet in the major sinks namely the biosphere, ocean and lithosphere based on their importance:

  • Organic molecules in living and dead organisms found in the biosphere;
  • As the gas carbon dioxide in the atmosphere;
  • As organic matter in soils;
  • In the lithosphere as fossil fuels and sedimentary deposits such as limestone, dolomite and chalk; and
  • In the oceans as dissolved atmospheric carbon dioxide and as calcium carbonate shells in marine organisms.

BIOSPHERE

Carbon dioxide is stored in the biosphere within living or recently dead plants, animals and microorganisms in the ocean and on land. The forests contain 86% of the planet earth’s carbon, with the Amazon rainforest in Brazil being one of the major sink for carbon dioxide the Amazon Rainforest (illustrated below showing a picturesque image of the largest rainforest in the world) is the only existing rainforest in the world today in terms of size and diversity.

It is worth noting that trees have hidden attributes and plays a key role in reducing pollutant levels in the atmosphere. Now trees are critically important in reducing the massive amounts of carbon dioxide pumped into the air by human activities this includes but not limited to the burning of fossil fuels, coals, oil and natural gas (a major driver for global climate change) and under natural environmental conditions, trees and plants from CO2 from the atmosphere and absorb it for photosynthesis.

Arial view of the Amazon Rainforest

Adopted: http://wwf.panda.org/what_we_do/where_we_work/amazon/about_the_amazon/why_amazon_important/

This is referred to the energy-creating process that allows oxygen to be released back into the air and carbon used by plants and trees to grow.

Importantly, without tropical rainforest and all forest as a matter of fact the greenhouse effect would likely be much more prominent and climate change could to a great extent worsen in the future if the trend of deforestation continues ultimately leading to less CO2 being transformed through photosynthesis the process responsible for life on earth.

This normal mechanism by which CO2 is removed from the atmosphere as it stands cannot cope with the quantities now being emitted into the environment leading to an enhanced greenhouse effect.

This system is intricately connected to animals since they receive carbon by eating plants followed by the release carbon dioxide into the atmosphere upon exhalation. Now, when animals and plants die, their carbon turns to fossil fuels after millions of years in the form of coal, oil and natural gas. The burning of these hydrocarbons in power plants and automobiles releases more carbon into the air and contributes to global warming.

LITHOSPHERE

Carbon is stored in the lithosphere in both inorganic and organic forms. Inorganic deposits of carbon in the lithosphere include fossil fuels like coal, oil and natural gas, oil shale and carbonate based sedimentary deposit like limestone. Organic forms of carbon in the lithosphere include litter, organic matter and humic substances found in soils. Some carbon dioxide is released from the interior of the lithosphere by volcanoes. Carbon dioxide released by volcanoes enters the lower lithosphere when carbon-rich sediments and sedimentary rocks are subducted and partially melted beneath tectonic boundary zones.

The carbon cycle also includes carbon dioxide dissolved in water, carbonate in sedimentary rocks like limestone and methane in the atmosphere. The element recycles through the atmosphere, down to plants, then into rocks and water before going back into the air. Carbon is not one of the most abundant elements on earth, but it is necessary for all life to exist.

OCEAN

In the open ocean environments the uptake of atmospheric carbon is primarily controlled by biological activities, seasonal and long-term changes in the heat content along with the overall chemistry of the surface and deep waters. In understanding atmospheric concentration of CO2 we must note that it is the impacted and uptake ecosystems play through the fixation of organic and mineral carbon by plankton productivity as well as the resulting sedimentation of particulate carbon through oceanic waters. It is extremely important to understand the role in which human activities play whether directly or indirectly as it pertains to the ocean carbon process, the ocean protects the climate and maintains its balance by absorbing and storing carbon dioxide by microscopic plants and animals.

Scientists believes that the ocean absorbs around 30-50% of the CO2 produced by the burning of fossil fuel and that is the ocean stopped absorbing these amounts the atmospheric CO2 levels would jump from a current level of 355 parts per million to 500-600 parts per million. The ocean has the greatest reservoirs of carbon, rapidly converting between an organic and inorganic state due to the short life cycle of phytoplankton.

Now ask me again why study the carbon cycle?

While convenient and easy to blame industrialization but what are we doing right not to curb the damages already done and to avoid future occurrences. We are all to be blamed for the almost all the increases in harmful / toxic gases being emitted daily in the atmosphere and even without the changes in CO2 to the atmospheric temperatures, excessive CO2 can alter the growth of plants around the world making too difficult for human and animals to source food which should alarm us.

ut never the less as we attempt to cut back on actions that increase the carbon dioxide (CO2) release into the environment more and more we realize that nothing is possible without complete agreement and that without awareness climate change is inevitable.

BY NAZINA BELLE

REFERENCE –

Pidwirny, M. (2006). “The Carbon Cycle”. Fundamentals of Physical Geography, 2nd Edition. [Date Viewed 27th January, 2015]. http://www.fibershed.com/education/carbon-cycle-curriculum/.

PMLE Carbon Program; 2015. Ocean Carbon Uptake [Website] Available at< http://www.pmel.noaa.gov/co2/story/Ocean+Carbon+Uptake> [accessed on 5 February, 2015].

Shrink that Footprint; 2015. Electricity Emissions around the World [Website] Available at< http://shrinkthatfootprint.com/electricity-emissions-around-the-world

> [accessed on 5 February, 2015].

Skeptical Science; 2015. Explaining how the Water Vapour Greenhouse Effect Works [Website] Available at< http://www.skepticalscience.com/water-vapor-greenhouse-gas.htm&gt; [accessed on 29 January, 2015].

Tutor Vista; 2015. Greenhouse Effect [Website] Available at< http://www.tutorvista.com/content/biology/biology-iv/environmental-changes/green-house-effect.php&gt; [accessed on 29 January, 2015].

UNEP; 1993. Oceans and the Carbon Cycle [Website] http://www.gdrc.org/oceans/fsheet-02.html&gt; [accessed on 5 February, 2015].

United States Environmental Protection Agency; 2014. Overview of Greenhouse Gases [Website] Available at< http://www.epa.gov/climatechange/ghgemissions/gases/co2.html> [accessed on 27 January, 2015].

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