How does mankind contribute to the carbon cycle

Beginning with the onset of the industrial revolution at the end of the last century, humans have been burning increasing quantities of fossil fuels as our primary energy source. As a consequence, the amount of CO 2 emitted from this burning has undergone an exponential rise that follows the exponential rise in the human population. This number also includes the CO 2 generated in the production of cement, where limestone is burned, liberating CO 2.

As you can see in the graph above, this flow has changed considerably over time, as human population has increased and as our economies have become more industrialized with a big thirst for the energy provided from the combustion of fossil fuels. The model we will work within the lab activity for this module includes this history, beginning in and going up to ; beyond is the realm of future projections, which can be altered to explore the consequences of choices we might make or not make in the future.

Part of the new energy economy that is key to our future is the use of so-called renewable energy sources, including wind, solar and geothermal energy, that emit little or no carbon. There are some interesting map view representations of this history of fossil fuel carbon emissions in the video below:. The other form of human alteration of the global carbon cycle is through forest cutting and burning and the disruption of soils associated with agriculture.

When deforestation occurs, most of the plant matter is either left to decompose on the ground, or it is burned, the latter being the more common occurrence. This process reduces the size the mass of the land biota reservoir, and the burning adds carbon to the atmosphere.

This provides the environment necessary for enhanced aerobic respiration by soil microorganisms. This decreases soil carbon, which can lead to erosion and soil degradation, and also releases additional CO 2 to the atmosphere.

As you learned in Chapter 5, biomass is an important form of energy to human civilization. Prior to the Industrial Revolution, this was essentially the only form of fuel to which most people on Earth had access. In many less-industrialized countries , combustion of biomass such as wood or animal dung is still the primary energy source that many citizens, particularly in rural areas, depend on for domestic use heating, sanitation, and cooking as it is inexpensive, relatively efficient, and readily available.

While the burning of biomass for domestic use contributes to some of these fires, it is the so-called slash-and-burn agriculture that makes up a larger contribution. If you need a refresher, use the CIA World Factbook website to view current global population growth values by country: www. While biomass burning still has a significant impact on the global carbon cycle, human impacts on fluxes such as fossil fuel extraction and combustion continue to grow.

For a review of the impacts of non-renewable energy sources such as fossil fuels, see Chapter 4. As countries become more industrialized, their reliance on and combustion of fossil fuels tends to increase. How has the use and distribution of fossil fuels changed throughout the past years? The effects of historic events such as the Great Depression of , World Wars, the fall of the Soviet Union in , and the Kuwait oil fires of can be seen.

Furthermore, between and , different regions have gone in and out of the lead position as top producer of CO 2 from fossil fuel emissions. Population is one reason why fossil fuel use has changed throughout time. This is particularly apparent when comparing the data for Western Europe to that of India and Southeast Asia. As countries industrialize, their relationship with agriculture also changes. More-industrialized countries rely very little on slash-and-burn agriculture.

Their agricultural practices, however, are no less impactful on the environment. The growing population Chapter 3 in many countries has required agriculture to become industrialized in order to meet demand. As a person living in the United States, industrialized agriculture probably produces the vast majority of the food you eat, including grains, fruits and vegetables, dairy and eggs, meats, and even fish.

One example of the impacts of industrialized agriculture is the production of methane CH 4 , a potent greenhouse gas. You will learn more methaneabout methane later in this section. As you saw earlier, methane is a common product of anaerobic metabolisms. The gut of ruminant animals such as sheep, cattle, and goats has evolved to allow the animals to digest the very tough carbon molecules, such as cellulose, in grass.

These land-use modifications began slowly many thousands of years ago and have accelerated in modern times with expanding population. This is the greatest source of atmospheric carbon from human activities. Carbon stored underground in coal, oil, and natural gas deposits for millions of years is being released into the atmosphere very quickly, creating a major imbalance in the cycle.

Carbon exists in the atmosphere primarily in the form of two gases: carbon dioxide CO 2 and methane CH 4. Even small increases in the concentration of these gases cause a warming effect. Climate Change. August 17, Modern family farms and family investments take many shapes;.

Global demand for food such as rice, alter our land and climate in complex ways;. Ocean: The ultimate carbon sink.