|
Biogeochemical Cycles
| |
While humans cannot control the weather on a daily basis, the influence of human life on the environment plays a significant role in global climate.
|
How often have you wished for a rainy day to go away, or for the warm weather of summer during wintertime? Unfortunately, these wishes rarely come true, and it seems as though humans have little control over the weather. While humans cannot control the weather on a daily basis, the influence of human life on the environment plays a significant role in global climate. Deforestation and fossil fuel burning are just a couple of examples of human activities that seriously disrupt the equilibrium of the global ecosystem and alter the biogeochemical cycles that play a role in determining the Earth’s climate.
Biogeochemical cycles are essentially the continuous transport and transformation of materials in the environment. Materials are transported through life, air, sea and land in a series of cycles. These cycles include the circulation of elements and nutrients upon which life and the earth’s climate depend. The most important biogeochemical cycles are those of water, carbon, nitrogen and certain other trace gases. In this text, however, we will discuss the carbon and nitrogen cycles, as they are closely intertwined with living things on Earth.
The carbon cycle is particularly influential when it comes to global climate. Much of the carbon in the carbon cycle is in the form of carbon dioxide, a gas that has a strong greenhouse effect because it absorbs infrared radiation. Carbon is one of the most common elements on Earth and it is the basis of all living things. Below is a graphical depiction of the carbon cycle:
|
|
| |
Carbon dioxide is used by plants for photosynthesis. The carbon is then built up into carbon compounds in the plants.
These carbon compounds either:
a) decay into peat, then over millions of years, coal (under very high pressures and worked on by microbes in the absence of oxygen). The coal is then burned by factories to produce electricity, and thus the carbon is returned to carbon dioxide in the air.
or
b) are eaten by animals (or remain in the plant, no difference). The carbon compounds in both the plants and animals are returned to the air as carbon dioxide via respiration and also when they die and decay, as microbes digest their biomass.
Thus the cycle is complete.
|
|
Nitrogen is another element that plays important roles in both biological and non-biological systems. Nitrogen gas makes up 80% of the Earth’s atmosphere and nitrogen exists in proteins of living organisms. The nitrogen cycle is depicted below:
 |
| |
Nitrogen in the air is built up into nitrates by nitrogen fixing bacteria. These nitrates are then absorbed by plants and turned into plant proteins. Leguminous plants can simply take the nitrogen in the air, and then build it up into plant proteins. The plant protein is then eaten by animals, who then excrete the protein as ammonia. Both the plant and animals proteins can be broken down and digested by microbes once the plant or animal dies into ammonia.
This ammonia is then oxidized by nitrifying bacteria into nitrites, which are then oxidized again by other nitrifying bacteria into nitrates.
Denitrifying bacteria can reduce nitrates to nitrogen in the air, nitrites or ammonia.
|
|
Global climate change, temperature, precipitation and the stability of ecosystems are all dependent upon biogeochemical cycles. When humans inadvertently disrupt these cycles by, for example, polluting, disastrous consequences can result. A healthy understanding of these cycles are critical in order to ensure the health and safety of future generations of living things on Earth. From climate changes to atmospheric composition, biogeochemical cycles are an integral component of planetary biology.
|
