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Carbon Cycle
All life is based on the element carbon.
• Major chemical constituent of most
organic matter, from fossil fuels to the
complex molecules (DNA and RNA).
• Living things are full of carbon!
Carbon Storage (Major Sinks)
• Organic molecules: living/dead
organisms (biosphere)
• Carbon dioxide gas (atmosphere)
• Organic matter (soil)
• Fossil Fuels (lithosphere)
• Sedimentary rock deposits: limestone,
dolomite, chalk (lithosphere)
• Carbon dioxide dissolved(hydrosphere)
• Calcium carbonate shells of marine
organisms (biosphere)
Carbon: Photosynthesis
Move C from Atmosphere to Plants:
• Autotrophic organisms: allows
absorption of CO₂ into cells.
• Add water and energy from the sun.
• Organisms use photosynthesis to
chemically convert the CO2 to carbonbased sugar molecules.
• Sugar, through metabolism, produce
complex compounds (proteins,
cellulose, and amino acids).
Carbon: Consumption
Move C from Plants to Animals:
• Pass some of the organic matter from
plants to animals through eating.
• Animals also consume other animals.
Carbon: Respiration
From Plants/Animals to Atmosphere:
• Carbon released from ecosystems as CO2 gas
through respiration.
• Respiration occurs in both plants and animals.
Carbon: Decomposition
Plants & Animals to Ground (lithosphere):
•
Decomposers break down organic matter (death, waste, decay).
•
Some becomes buried miles underground to become fossil fuels
after millions and millions of years.
Carbon: Combustion
From Fossil Fuels to Atmosphere:
•
Humans burn fossil fuels to power factories, power plants, vehicles.
•
Most of the carbon is CO2 gas.
Each year, 5.5 billion tons of carbon is released by burning fossil fuels= weight
of 100 million adult African elephants!
•
Of this amount, 3.3 billion tons enters the atmosphere.
•
Most of the rest dissolves in seawater.
Today’s Atmosphere
HOWEVER: Recent Increase of CO₂:
•
Industrial Revolution: humans greatly increased CO₂ in the
atmosphere /oceans
•
The atmosphere has not held this much carbon for at least
420,000 years (ice cores data).
•
Scientists estimate future CO₂ levels could reach between 450
to 600 PPM by 2100.
•
More greenhouse gases (CO₂,+) in the atmosphere cause our
planet to warm.
•
Major CO₂ sources: fossil fuel combustion & changing natural
plant cover (grassland, woodland, & forest ecosystems)
•
Combustion emissions = 65% of CO₂
•
Other 35% = Deforestation & converting natural ecosystems to
agricultural systems.
•
Natural ecosystems can store between 20 to 100 times more
CO₂ than agricultural land-uses.