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Carbon and the Earth: Interactive Labs, Part 3 Feedback EffectsI have consolidated the background, instructions, and questions from the web site in this handout so you can concentrate on the simulator on your computer.Got to: 1So far we have considered only the impact of burning fossil fuels. But there are other human activities that influence the carbon cycle. One major factor is deforestation and land use. Currently, land use (for example, rice paddies) and deforestation outstrip reforestation by roughly 1 GT per year. If deforestation were to increase, perhaps due to increased burning of rainforests, carbon would be transferred first from terrestrial plants to the atmosphere and then through the rest of the carbon cycle as seen previouslyChange the net deforestation rate and observe how that impacts the carbon cycle. Note that deforestation is expressed as GT of carbon released, not as a percentage rate of increase. Realistic deforestation estimates would remain less than 2 GT per year. Record what happens to the system at a steady net deforestation rate of 1.6 GT per year and answer the following:By 2090, how has the terrestrial flora population changed? What is the carbon level in the soil and how does the carbon level affect the flora populations and species variety?Compare this chart to the first one you made.In 2070, how are soil carbon levels different? In what ways will this difference in soil carbon level manifest itself?By 2070, how might the worldwide decomposer populations change? What effects could “business as usual” and the last rate of deforestation you selected have on human health?Step 2There are several important natural systems that may be affected by greenhouse warming as atmospheric CO2?rises. Some of these systems may release even more CO2?into the atmosphere, speed up the warming, and cause a positive feedback loop. Which feedback effects will actually take place is hard to predict in such a complex system, but a model for one feedback effect is included in the simulator: melting tundra. If the arctic tundra were to melt as temperatures rise, its stored carbon would enter the system. You will find two possible scenarios. One model assumes that 1/12 of the tundra will melt over 100 years. The other predicts that 1/6 will melt over that same time period.Assume that, in this hypothetical scenario, the tundra melting is inevitable and there is a 2% increase in fossil fuel consumption. Which of the two rates of melting would:Have an impact on coastal seaweed populations in 2060? How great an impact?Have an impact on atmospheric carbon in 2110 that is similar to another scenario you’ve investigated? What commonalities exist between these two scenarios?For your consideration:As you have seen in this lab, despite the natural tendency of the carbon cycle to regulate the amount of carbon in the atmosphere, the system is currently being overwhelmed by human fossil fuel combustion and deforestation. If this increase in atmospheric CO2?results in temperature rise as scientists predict, there are several possible factors that could cause feedback effects. If human beings are to mitigate these risks, they will have to take strong action soon.What are some viable ways of lessening the effect that increased carbon has on the following?Impact on human lifeDestruction of the cycleGlobal warmingAlteration/destruction of species, biomassThe carbon cycle is only one of many natural (and human "enhanced") cycles: hydrogen, water, nitrogen, and oxygen are some other cycles you may want to investigate. Think about how these cycles have changed due to human impact. ................
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