Global Biogeochemical Cycles
When nutrients leave on ecosystem and enter another
The movement of ions and molecules among ecosystems links local biogeochemical cycles into
one massive global system.
The Global Water Cycle
Water evaporates out of the ocean and precipitates back into it; evaporation exceeds
When this water vapor moves over the continents, it is augmented by water transpired by
plants. Precipitation falls on the continents.
The cycle is completed both by water that moves from the land to the oceans via streams and by
groundwater; water that is found in soild.
Humans are affecting the water cycle in many ways. One of the most direct ways is in
groundwater storage. The water table, the upper limit of saturated soil, is dropping on every
The Global Carbon Cycle
The global carbon cycle involves the movement of carbon among terrestrial ecosystems, the
oceans, and the atmosphere.
The oceans is by far the largest of these three reservoirs. Carbon moves into and out of the
atmospheric reservoir rapidly via the photosynthesis and respiration of organisms.
Local Carbon Cycle- purple arrows show movement of carbon. Oxygen moves in the opposite
direction as carbon. Photosynthesis releases oxygen into the atmosphere. Respiration,
decomposition and burning take oxygen from the atmosphere.
Carbon Storage- storage of carbon in detritus and then fossil fuels maintains higher
atmospheric O . Carbon storage in soils now varies globally. Carbon storage has varied over
There are high levels of carbon storage in boreal forests and tundras, particularly in wetlands.
Acidity and anoxia slow decomposition.
Carbon dioxide is a greenhouse gas; a gas that traps heat radiated from Earth and keeps it from
being lost to space.
Increases in the amounts of greenhouse gases have the potential to warm Earth’s climate by
increasing the atmosphere’s heat trapping potential.
Human activities such as intensive agriculture, deforestation and burning of fossil fuels have
changed the carbon cycle by adding large amounts of carbon dioxide to the atmosphere.
A kind of tropical forest on seacoasts, have very high carbon storage
Continent of Pangea was forming. Climate was tropical, many shallow wetland swamp forests
with periodic flooding. This led to high levels of carbon storage