Human-Induced Changes on Biogeochemical Cycles

Human Induced Changes on Biogeochemical Cycles

The Carbon Cycle

The Industrial Revolution occurred in 1750, and since then, human society has been using a lot of energy. We get this energy by burning coal, oil, and natural gas–also known as fossil fuels. This, along with the use of wood as fuel and the burning of large sections of tropical forests has taken large amounts of carbon from underground deposits and shifted it into the air. Pre-Industrial Revolution, CO2 made up 0.029% of the atmosphere, and it now makes up 0.038%, and it is predicted to take up 0.06% by the end of the century. The increase in CO2 is causing human-induced global climate change, causing increasing temperature, a rise in sea level, disrupted precipitation patterns, increased wildfires, flooding, drought, heat waves, extinction of organisms and agricultural disruptions.

The Nitrogen Cycle

In the 20th century, humans increased the amount of fixed nitrogen (nitrogen chemically combined with hydrogen, oxygen, or carbon) used. It is most commonly used in fertilizer. Rain washes nitrogen from the fertilizer into rivers, lakes, and coastal areas, where it promotes bacterial growth that deprives the water of dissolved oxygen, causing many aquatic species to suffocate. The nitrogen can also dissolve and wash down through the ground and contaminate groundwater–which is dangerous for humans to drink. Combustion of fossil fuels also affects the nitrogen cycle. The high temperatures can sometimes change atmospheric nitrogen into nitrogen oxides which make a dangerous photochemical smog. The reaction of this with water in the atmosphere forms acids that leave the atmosphere as acid deposition and decrease the pH levels of surface water and soils.

The Phosphorus Cycle

Humans accelerate the long-term loss of phosphorus from the phosphorus cycle. Most of it is discarded in waste, and much of it is washed away into the ocean, where it is permanently lost, for it remains there for millions of years. It enriches the water and can lead to undesirable changes. The way to combat this is to try and recycle phosphorus from sewage. 

The Hydrologic Cycle

Air pollution may weaken the hydrologic cycle, aerosols produced from fossil-fuel combustion and burning forests create clouds that are less likely to release their precipitation, affecting the availability and water quality in some regions.