Earths Life Support System 4. To what extent are the water and carbon cycles linked?

  • Created by: DanBish
  • Created on: 05-05-22 18:55
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  • To what extent are the water and carbon cycles linked?
    • The two cycles are linked and inter-dependent
      • Human impacts on Carbon Cycle
        • Human activity affects the carbon cycle by decreasing the store of carbon in the lithosphere and increasing the store of carbon in the atmosphere.
          • Humans burn fossil fuels, releasing energy, and carbon dioxide product. This transfers carbon from the lithosphere to the atmosphere.
            • However, we're using more and more fossil fuels each year, and are slowly depleting the finite store
        • Human activity affects the carbon cycle by influencing the amount of carbon stored in the biosphere by either causing deforestation or re afforestation.
          • Deforestation contributes 3 billion tonnes of carbon to atmosphere each year.
            • Tropical forests are deforested for a variety of reasons: to clear land for agriculture, for mining, for urbanisation and infrastructure projects.
      • Human Impacts on Water Cycle - Local and Regional/ National
        • Local - Evapo-transpiration has reduced by ~20% Surface runoff has increased greatly Groundwater stores are much less Interflow (infiltration) rates have dropped too.
          • Trees  removed, reducing transpiration. Less interception so less interception loss so there will be more surface storage. Urbanisation makes ground impermeable so less infiltration and so less percolation, causing increased surface runoff + less water stored as groundwater.
        • Regional/ National - Aral sea dams. Large amounts of dams placed over Kazakhstan
          • Since 1960 over 80% of the water in the Aral Sea has disappeared and it is predicted to dry up totally by 2050.
            • Rivers feeding Aral Sea dammed and water used for irrigation in Kazakhstan, causing the sea to begin drying up, increasing amount of salt in soil. poisoned plants + animals. Camel herders lost  livestock, fishermen lost jobs. Factories closed down. A new dam built to keep water in small Aral Sea.
    • The global implications of water and carbon management.
      • Managing Carbon Cycle
        • Afforestation
          • Deforestation not only removes the carbon sink of the forest but if the trees are removed by slash and burn techniques the carbon stored within the trees is rapidly added back to the atmosphere. 
          • Afforestation will result in more carbon flowing from the atmosphere to be stored in the biosphere.
          • The Bonn Challenge is a global initiative to restore 350 million hectares of forest by 2030. As of 2017 44 countries have pledged that 151 million hectares will be reforested.
        • Wetland restoration
          • Wetlands are a carbon sink, as water logged conditions slow de-composition, becoming peat
          • Great Fen - Wetland restoration project in UK. 870ha wetland now, 3700ha by 2050
        • Changing agricultural practises
          • Livestock rearing - Making feed production more efficient, limiting methane output
          • Rice cultivation - Using limited fertilisers, limiting the amount of time the fields are flooded, less bacteria producing methane
          • Soil management - reducing erosion helps stop land being degraded, conserving soil organic matter, preserving the soil carbon sink
        • International agreements
          • Paris Agreement (2015)
            • Limit global warming to below 2C and limit to a max of 1.5C above pre-industrialised levels. 
              • Other countries set own targets and policies
          • European Union Emissions Trading Scheme
            • All participants given level of emissions. If the cap not met, the unused emissions can be sold to others. If cap exceeded, un-used emissions must be bought.


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