Changes to the carbon cycle

• Urbanisation

  Urban growth reduces the amount of surface vegetation.

  Carbon dioxide emissions from energy consumption, transport and industry increase.

  Increase in carbon dioxide emissions from cement manfacture.
• Forestry

  Changing land use to forestry increases carbon stores.

  Forest trees extract carbon dioxide from the atmosphere and sequester it for hundreds of years via the wood of the tree stem.

  Forest trees are only an active carbon sink for the first 100 years or so after planting and so forestry plantations usually have a rotation of 80 to 100 years.
• Farming practices

  Clearance of forest for farming reduces above and below ground carbon stores.

  Ploughing reduces soil carbon storage and exposes soil organic matter to oxidation.

  Harvesting means that only small amounts of organic matter are returned to the soil, further reducing carbon stores.

  Rice paddies generate methane.

  Livestock release methane gas as a by product of digestion.

  Emissions from tractors increase the level of carbon dioxide in the atmosphere.
• Volcanic activity

  Volcanic explosions release a large amount of sulfur dioxide into the upper atmosphere.

  Reducing the amount of incoming solar radiation, but is counterbalanced by the absorption of outgoing terrestrial radiation by greenhouse gases emitted.

  THEREFORE, resulting impact uncertain.
• Fossil fuel combustion

  Approximately 10 billion tonnes of carbon dioxide are released into the atmosphere annually.

  Anthropogenic carbon emissions impact the atmosphere, oceans and biosphere most significantly are the the leading cause of global warming;

  i.e. Geological stores to the atmospheric store and the oceanic store