Carbon Cycle - Human Activity Affecting the Cycle & Feedbacks

Tundra & Permafrost:
  • This is positive feedback as Arctic warms: The Arctic is going to increase in temperature by 7.
  1. GHG increase concentration leading to more global warming
  2. Warming air temperatures and more melting snow
  3. Soil warms up from warmer air and absorbing sunlight
  4. Soil thaws as ice melts
  5. More methane is released
  6. More decomposition occurs of dead organic matter releases CO2.
Biological Carbon Cycle:
  • Marine ecosystems e.g. phytoplankton (algae), coral reefs and terrestrial ecosystems e.g. forests, wetlands, grassland, tundra
  • Humans place huge pressures on these ecosystems through pollution, over-abstraction, climate change, and land-use change e.g. deforestation and conversion of natural habitats into farmland
  • Growing demand for food increases pressures on natural environments e.g. land-use change
  • More demand for fuels such as biofuels in Brazil increase pressures as well
  • This ‘degrades’ the carbon cycle as there are less carbon stores, and more CO2 is emitted, e.g. from forests, DOM from soils, and the ocean
  • Some areas however are improving and act as CO2 sinks e.g. afforestation programmes – which in turn improves the carbon and water cycle functioning, and also ecosystem resilience
Problems for the Amazon:
  1. Deforestation: 20% of the rainforest has already gone – which is the biggest issue
    1. Main cause is cattle farming. 70% for beef. Other grasslands increasingly used for biofuels so cattle farmers are forced to clear the rainforest even more.
  2. Future climate change methods such as droughts.
Coral Reefs & Ocean Acidification:
  • Act as a home for 25% of all marine life.
  1. Carbon dioxide concentration is increasing in the oceans sink due to more diffusion from the atmosphere.
  2. Water is slightly more acidic. Small reductions in pH, destroying coral reefs ecosystem.
  3. Corals are calcium carbonate so positive feedback could affect the carbon cycle.
The Tipping Point:
  • A point might be reached when there is no going back. Climate change has accelerated and becomes uncontrollable.
    • Positive feedback becomes so strong and keeps growing and so GHC becomes strong. And CO2 spirals out of control causing huge climatic forces and global warming at a huge scale.
Energy Consumption Increasing:
  • Energy is increasing up until 2020.
  • Consumption is also increasing.
Climate Belt Shifting:
  1. Rainforest could shrink due to more droughts and forest fires, releasing carbon and storing less
  2. Deserts will spread as temperatures evaporation and droughts increase e.g Sahel grasslands will shrink as Sahara grows
  3. Alpine areas will shrink as mountains warm up and glaciers mean snow melts earlier.
  4. Tundra areas (frozen soil in the Artic) will shrink as coniferous forests move north.
Climate Change Affecting Forests:
  • Rising air temperatures means more climate variability, less snow along with faster and early snowmelts. Floods may be more impacted to the ability to store water.
  • Warmer water bodies mean altered forest habitats – drier vegetation, increased pathogens and fire.
Changes to Conventional Rainfall:
  • 60% of the Amazon rainfall is from evapotranspiration water from forests.
  • Biomass carbon in plants and trees will decrease.
  • Dead organic matter will decompose and decrease also release more CO2
  • Water cycle disruption will include less precipitation, interception, lower soil moisture, less storage and maybe more flooding.
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