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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.