Global Carbon Cycle

Global Carbon Cycle

Organic compounds contain the carbon element and are present in living things. Carbon always moves within the earth’s atmosphere, biosphere, hydrosphere and lithosphere. In rocks, carbon moves as calcium carbonate, in living organisms as carbohydrates or sugars and the atmosphere as carbon dioxide (CO₂). The carbon cycle among earth spheres starts with green plants which absorb the CO₂ from the atmosphere through photosynthesis producing carbon-containing sugars. From the plants, animals eat the plants obtaining sugars from chlorophyll trapped during photosynthesis. CO₂ is released to the atmosphere when the animals break down the carbohydrates through respiration and when they decay. Fossil fuels- oil, coal and natural gas are produced when dead animals and plants decay under high temperatures and high pressure. These fossil fuels are in turn used by human beings for heating, operating machinery and other purposes. When people burn these fossil fuels to produce energy, carbon dioxide levels in the atmosphere also increases, and the cycle begins.

Deforestation and slash burning of forests

The carbon stocks remaining in forests around the world are currently at risk due to deforestation. Human beings are cutting down trees for various reasons including creating space for growing crops to feed their families and build social status, for building space such as industries that require large areas of land and for wood to make furniture, paper and others.  Even though deforestation is having a terrible effect on the earth’s climate and oceans, it is not easy to stop it because our world depends mostly on timber to make the most commonly used equipment.

Impact of deforestation: trees and forests balance the amount of carbon in the atmosphere through the process of photosynthesis, where plants make their food with carbon dioxide. When we have excess carbon dioxide in the atmosphere, a blanket of CO2 is created, which then traps heat and prevents it from leaving the earth surface in the atmosphere. The excess heat warms the earth, and much of it causes global warming.

Consequences include:

Loss of ecosystems and habitats for the animals and plants. This will cause death and species becoming extinct. Air pollution, global warming and greenhouse gas problems because there will be no enough plants and trees to take in CO2 and produce O2 thus, humans will lack oxygen to breathe and live.

Burning of fossil fuels

Carbon is released into the atmosphere at a faster rate than it is absorbed when coal or oil is burned. This results to increase in carbon dioxide concentration in the atmosphere. The major contributors of this saturation are burning fossil fuels, use of limestone to make concrete and changing land use.

Burning Fossil fuels impacts on earth, oceans and the climate. Fossil fuels release carbon dioxide at a faster rate leading to an increase in temperatures; this directly impacts on the growing season. The carbon dioxide produced from fossil fuels also traps heat in the atmosphere contributing significantly to global warming. Oceans and water bodies are greatly impacted by the contribution of excess carbon dioxide in the atmosphere caused by fossil fuel. Seas and oceans absorb a lot of human-made carbon emissions altering with the basic chemistry of the ocean. This leads to acidification which impacts flora and fauna living in the oceans. The increase in temperatures accelerates ice loss rate, drying up of rivers and leading to deaths of some animals.

Exponential Growth and Logistic Growth

Logistic growth is a specific way that the population’s per capita growth rate decreases as a population reach a carrying capacity which is imposed by limited resources. Exponential growth, on the other hand, reflects the population per capita growth rate that starts slowly but gains momentum with an increase in population size. The graphs below show the difference between exponential and logistic growth.

Exponential Growth

Population

Size

(N)

Time

Exponential and Logistic growth are both population growth theories. Exponential growth is mainly characterized by a J-shaped curve while Logistic growth, an S-shaped curve. Unlike Logistic growth which stats rapidly, Exponential growth begins at a slower rate and speeds up with population rise. The exponential growth model shows a characteristic curve which is J-shaped while the logistic growth model shows a typical curve which is S-shaped.

Of the two population models, Logistic growth applies to populations that reach carrying capacity, unlike Exponential growth which applies to populations without a growth limit. This makes logistic growth model more realistic and applicable to several different populations, unlike exponential growth model, which is ideal for populations with unlimited space and resources. Both exponential and logistic growth happens when the growth rate is proportional to actual amounts, but logistic growth includes limitations of resources and competition. This is because the exponential growth lacks an upper limit, unlike logistic growth which has the carrying capacity as the upper limit.

Logistic Growth

Carrying Capacity

K

Population

Size

(N)

Time

Population Change

The world population reached one billion in 1800 reflects a slow and even growth. These numbers started rising slowly but steadily to reach 2.5 billion by 1950 after the industrial revolution. This number has grown to unprecedented levels of 7.77 billion people by 2020 more than tripling in 70 years.

The pre-industrial period is characterized by a lot of factors that promoted a high death rate, including lack of knowledge of preventing and curing diseases, food shortages, outbreaks of infectious diseases. Diseases such as influenza or plague which had no cure at that time, coupled with a lack of clean water and inadequate sewage disposal practices led to low child mortality rate. This was attributed to sicknesses such as cholera, TB, typhoid, measles which are now causing little deaths. The demographic transition started with the industrial revolution, which improved food supplies through advanced agricultural practices, and industrial processes which developed the medical industry.

The growth of the medical industry is one substantive force that impacted population growth for it improved mortality rates lowering the death rates. Cures and vaccines of pre-industrial diseases meant a reduction in death rates. The technological developments over time in the medical sector mean improved life expectancy rate and fertility rates which are all drivers of population growth. This increase in mortality rate has impacted on the age structure of the world, meaning more youths who are fertile and as such, an increase in the birth rate. Therefore, the rise in birth rate and a decrease in death rate means a positive growth in population.

Environmental Threats

It is no secret that increases in the number of people require an increase in resources which means that as the population increases, the earth’s resources are depleted more rapidly. It is then expected that humans will be forced to strip the earth of its resources to accommodate the rising numbers over time. This is true because human activity as at now has led to substantial global warming through the burning of fossils and other greenhouse gasses. The loss of biodiversity by the destruction of habitats through the clearing of forests impacts the environment significantly.

Use of resources per person equally affects the environment. While people in developed countries will resort to increasing the resources to maintain their lifestyle, those in developing countries feel the impact of environmental problems more severely. The most vulnerable areas experience decreases in access to clean water and increased exposure to diseases and air pollution. From my point of view, yes, we have severe effects looking at resources per person. which include water pollution, soil degradation, and overconsumption. Still, humans can make positive changes even though the problems of population growth and environmental issues seem overwhelming. We can resort to using only the resources that the earth provides indefinitely like solar or wind power instead of burning fossil fuels.

References