Human activities cause changes in water and carbon stores

  • Created by: EmilyM17
  • Created on: 21-05-19 12:50
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  • How human activities cause changes in the availability of water and carbon
    • Rapid population and economic growth, deforestation and urbanisation in the past 100 years have modified water and carbon cycles. Impact of these changes is most apparent at the regional and local scales
    • Water Cycle
      • Impact most evident in rivers and aquifers.
        • Rising demand for water for irrigation, agriculture and public supply, especially in arid and semi-arid environments, has created acute shortages
          • EXAMPLE
            • Colorado Basin in the southwest USA
              • Surface supplies have diminished as more water is absracted from rivers and huge amounts are evaporated from reservoirs, like Lake Mead
      • The quality of freshwater resources has declined.
        • Overpumping of aquifers in coastal regions has led to incursions of salt water, often making water unfit for irrigation and drinking
          • EXAMPLE
            • Bangladesh
        • EXAMPLE
          • Bangladesh
      • Deforestation and urbanisation reduce evapotranspiration and therefore increase precipitation, increase run-off, decrease throughflow and lower water tables
      • EXAMPLE
        • Amazonia
          • Forest trees area key component of the water cycle, transferring water to the atmosphere by evapotranspiration which is the returned through precipitation. Extensive deforestation has broken this cycle, causing climates to dry out and preventing regeneration of the forest
    • Carbon Cycle
      • Depletes some carbon stores and increases others
        • Depletion
          • World replies on fossil fuels for 87% of its primary energy consumption. The exploitation of coal, oil and natural gas has removed billions of tonnes of carbon from its geological store- heightened by industrialisation
            • Additional carbon is stored as atmospheric CO2 where its concentration increases year by year.
              • Increases
            • Around 2.5 million tonnes is absorbed by the oceans, and a similar amount by the biosphere
              • Increases
      • Deforestation
        • Reduced forest cover in historic times by nearly 50%
          • Thus, the amount of carbon stored in the biosphere and fixed by photosynthesis, has declined steeply
      • Photosynthesis by phytoplankton
        • Phytoplankton absorb more than 1/2 the CO2 from burning fossil fuels.
          • Acidification of the oceans threatens this vital biological carbon store as well as adversely affecting marine life
      • Soil
        • Important carbon store being degraded by erosion caused by deforestation and agricultural mismanagement.
      • Wetlands
        • Carbon stores drained for cultivation and urban development, have also been depleted as they dry out and are oxidised

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