Carbon Cycle - Human Activity in the Carbon Cycle

Carbon Cycle Balance:
  • The natural ‘greenhouse effect’ is how our atmosphere and ‘greenhouse gases’ trap heat from the sun
  • Keeps the world warmer than it would be without natural greenhouse gases so the world average would be at least -18 0C (average now is around 15 0C).
  • The main greenhouse gases are CO2 (carbon dioxide) and CH4 (methane).
  • The greenhouse affect therefore heavily influences the patterns of temperature and precipitation around the world.
  • Photosynthetic organisms (e.g. plants, phytoplankton) and soils help regulate the climate by helping control the atmospheric composition.
  • However, humans have altered and tipped the balance of the carbon pathways and cycle.
Reasons For Greenhouse Gas Emissions:
  1. Population growth: increases all reasons below
  2. Transport: oil in USA for cars
  3. Industry: China No1 for coal burning (for electricity)
  4. Development: electricity generation as countries get richer
  5. Agriculture: More cows and rice fields to meet demand emit methane gas
  6. More energy use per capita (standard living improving)
  7. Deforestation: releases carbon dioxide e.g. Amazon rainforest
Terrestrial Regulation Of The Atmosphere:
  • The terrestrial biological stores include vegetation, soils and leaf litter
  • Forests are the main ecosystem stores
  • The climate effects the ecosystem carbon store size, and also the fluxes in the system
Carbon Nutrient Cycling Is Important For Soil Health:
  1. Input: Nitrogen, carbon and minerals
  2. Output: Lose of nutrients by leaching and runoff
  3. Flows: Leafs and needles fall from biomass to litter and uptake of nutrients from the soil.
Summary:
  • On a short-term timescale, the carbon cycle is naturally balanced (dynamic equilibrium).
  • Photosynthesis and respiration from terrestrial ecosystems (vegetation and soils) balance.
  • Oceans have the biological, carbonate and physical carbon pumps.
  • Climates determine how ecosystem productivity varies, such as rainforest biomass carbon stores being largest, but deserts storing more carbon in soils
  • Outgassing-from and diffusion-into the oceans roughly balances
  • However, anthropogenic sources e.g. fossil fuels for CO2, methane from agriculture, have created a new large input.
  • This increases atmospheric GHG levels, and fluxes slightly change as the system absorbs more CO2.
  • The human enhanced greenhouse effect means that global climate, ecosystems, and hydrological cycle will change e.g. more storms, rainfall, droughts, forest fires, floods, migration etc.
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