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Similar term(s): Biogeochemical cycles, nutrient cycles.
A natural process in which elements are continuously cycled in various forms between different compartments of the environment (e.g., air, water, soil, organisms).
Examples include the carbon, nitrogen and phosphorus cycles (nutrient cycles) and the water cycle.
Source: GreenFacts
Carbon Cycle
Nitrogen cycle
Photsphorus cycle
Water cycle
The carbon cycle includes the uptake of carbon dioxide by plants through, its ingestion by animals and its release to the atmosphere through respiration and decay of organic materials. Human activities like the burning of fossil fuels contribute to the release of carbon dioxide in the atmosphere.
The nitrogen cycle involves the uptake of nitrogen form the atmosphere by a process called fixation which is carried out by microbes or industrial processes. Decomposition of biological waste by microbes can return nitrogen to the atmosphere. Nitrogen is mainly used by humans as a fertilizer in farmlands, but its excessive usage can lead to serious problems (such as eutrophication).
The phosphorus cycle involves the uptake of phosphorus by organisms. Phosphorus in the environment is mainly found in rocks, and natural weathering processes can make it available to biological systems. After decomposition of biological waste, it can accumulate in large amounts in soils and sediments. Phosphorus is used by humans as a fertilizer in farmlands and in detergents. Overuse of phosphorus can lead to eutrophication.
The water cycle is the process by which water travels in a sequence from the air (condensation) to the earth (precipitation) and returns to the atmosphere (evaporation). It is also referred to as the hydrologic cycle.
Human use of water can transform the water cycle through irrigation or the construction of dams, for example.
GreenFacts Summary on Ecosystem Change:
Español: Ciclo medioambiental
Français: Cycle naturel
Nederlands: Milieucyclus
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