Question

Earth Science: How Humans Alter Cycles

Answer 1

You know that the nitrogen cycle, carbon cycle, and water cycle move substances throughout the environment. These cycles are natural and occur as the result of a driving force, usually sunlight. But now we have to consider what impact human life and activities have on these cycles. For thousands of years, humans have been altering, interrupting, aiding, and accelerating the biogeochemical cycles. Farming, fires, burning fossil fuels, and paving roads can all have an impact on these cycles.Moving nitrogen compounds into the air or water affects the nitrogen cycle.

Nitrogen moves from the air, to soil, into living things, and then back into the air.

Humans introduce more nitrogen into the water supply in several ways. Sewage treatment plants release dissolved nitrogen compounds into the surrounding water supply. Adding fertilizers to crops can also be problematic. Many fertilizers are rich in nitrogen compounds, and as we know, plants need these to grow. Excess fertilizers will often enter a local water supply as runoff. Too many nitrogen compounds in an ecosystem can lead to eutrophication . Eutrophication is the rapid growth of algae in a body of water that reduces the amount of dissolved oxygen in the water and kills other organisms living there.Human activity adds nitrogen to the atmosphere.

Excess nitrogen in the atmosphere alters the cycle as well. Some industries and exhaust from motor vehicles release nitrogen and sulfur compounds into the air. In the atmosphere, these compounds combine with water to form nitric acid and sulfuric acid, significant components of acid rain .

But, the actions of humans on the nitrogen cycle are not entirely negative. Farmers will often rotate their crops, planting legumes such as clover, peas, or alfalfa every few years. Legumes have the bacteria needed for nitrogen fixation on their roots. Planting legumes every so often allows the nitrogen content of the soil to be replenished.The human alteration of the carbon cycle is fairly significant.

Humans alter the movement of carbon from living things to nonliving parts of the environment in many ways. Deforestation is a significant culprit. Clearing land for farming or lumber is often done by burning trees. Burning wood releases carbon dioxide into the atmosphere. Removing trees from the environment also decreases photosynthesis in the area, reducing the amount of carbon dioxide that is removed from the air by that process. Cutting down trees and burning them ultimately accounts for about 20 percent of the carbon dioxide that is added to the atmosphere by human activity.About 80 percent of the carbon dioxide attributed to human activity is from the use of fossil fuels.

The use of fossil fuels, such as petroleum, natural gas, or coal, releases carbon dioxide into the atmosphere. This is alarming because of its contribution to global warming. Carbon dioxide is a greenhouse gas. It traps the heat from the sun close to the surface of earth.The excess carbon dioxide that enters the atmosphere due to deforestation and the burning of fossil fuels is predicted to have a negative impact on global temperatures for years to come.

Human activity alters the water cycle as well.

Water enters the atmosphere through evaporation or transpiration. How might the water cycle be affected if deforeststation takes place on a large scale? Without trees and plants to introduce water into the atmosphere by way of transpiration, the water cycle will change. Specifically, precipitation patterns will shift, which will affect the ecosystems that rely on that precipitation.

Other human activities alter the water cycle, too.

Stresses on a water supply can influence the water cycle. Sometimes the overuse of water leads to a situation where water is removed from the environment faster than it can be replenished. For example, overuse of an aquifer for irrigation or household purposes can lead to depletion of the water supply in that aquifer. Human activity reduces the water purification abilities of the water cycle. Water that moves along the surface as runoff is less clean than water that moves as groundwater. The paving of large areas of land, such as parking lots, reduces the amount of infiltration. Water runs to the larger bodies of water along the surface, accumulating contaminants along the way.Human activity affects biogeochemical cycles.

Human activity has a major impact on water and air quality, leads to a global rise in temperature, and alters weather patterns globally. An activity can adversely affect more than one cycle. Deforestation affects the carbon and water cycles. Burning fossil fuels has an impact on all cycles. We need to seek alternatives to our actions to conserve and preserve essential biogeochemical cycles.