2. THE CARBON CYCLE

3. What Is Carbon? Carbon is a key element for life, composing almost half of the dry mass of the earth’s plants (that is, the mass when all water is removed). The basis of life of earth Found in rocks, oceans, atmosphere

4. Carbon Cycle The same carbon atoms are used repeatedly on earth. They cycle between the earth and the atmosphere

5. Plants Use Carbon Dioxide Plants pull carbon dioxide from the atmosphere and use it to make food –— photosynthesis. The carbon becomes part of the plant (stored food).

6. Animals Eat Plants When organisms eat plants, they take in the carbon and some of it becomes part of their own bodies.

7. Plants and Animal Die When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere. Some are not decomposed fully and end up in deposits underground (oil, coal, etc.).

8. Carbon Slowly Returns to Atmosphere Carbon in rocks and underground deposits is released very slowly into the atmosphere. This process takes many years. The carbon cycle is the exchange of carbon among three reservoirs or storage places: the land, the oceans, and the atmosphere.

9. The global carbon cycle is usually thought to have four major carbon sinks interconnected by pathways of exchange. These sinks are; the atmosphere, the terrestrial biosphere (which usually includes freshwater systems and non-living organic material, such as soil carbon), the oceans (which includes dissolved inorganic carbon and living and non-living marine biota), and the sediments (which includes fossil fuels ).fossil fuels

11. Figure 1. Magnitudes of the reservoirs (sinks) of actively cycling CO2 in gigatons of carbon. Of the ocean pool, roughly 1,000 Gt are in contact with the atmosphere in any given decade. The terrestrial biosphere consists of soil (ca. 1,600 Gt) and vegetation (ca. 600 Gt). Data from Schimel et al. (1995).(after Christensen, 1991).

13. The mechanism of the problem Anthropogenic activities which upset the carbon cycle include burning of fossil fuels and deforestation. Fossil fuels, such as oil, coal and natural gas, are the fossilized remains of prehistoric plants and animals and represent stored carbon.

15. Cycle – Repeats Over and Over and Over and Over …

16. Carbon in Atmosphere Plants use carbon to make food Animals eat plants and take in carbon Plants and animals die Decomposers break down dead things, releasing carbon to atmosphere and soil Bodies not decomposed — after many years, become part of oil or coal deposits Fossil fuels are burned; carbon is returned to atmosphere Carbon slowly released from these substances returns to atmosphere Carbon Cycle Diagram

17. The Carbon Cycle

18. Environmental Impact Deforestation has two impacts: the breakdown of carbon in the bi- products of the wood and the loss of trees to draw carbon dioxide out of the atmosphere. Global Warming Air Pollution Climate Change

19. Human Impact Fossil fuels release carbon stores very slowly Burning anything releases more carbon into atmosphere — especially fossil fuels Increased carbon dioxide in atmosphere increases global warming Fewer plants mean less CO 2 removed from atmosphere

20. Mitigation A process called carbon sequestering involves planting new forests to reduce atmospheric carbon dioxide concentrations. The greatest opportunity for this is in tropical areas where growth rates are the fastest.

21. What We Need to Do? Recommendation: Taking Action We already possess the scientific, technical, and industrial know how to solve the carbon and climate problem for the next half- century. A concept known as “carbon wedges” proposes to limit the human contribution to the global carbon cycle, in an effort to reduce global warming. Adoption of the wedge concept is essential if we are going to curb our extraordinary abuse of fossil based fuels.“carbon wedges” Burn less, especially fossil fuels Promote plant life, especially trees