Human+Impact+on+Natural+World+HW5+MC

Human Interference with the water cycle (p.499) 1. What are the three ways humans disrupt the natural water cycle? First they withdraw water from aquifers; second they clear vegetation from land and build roads and buildings that prevent percolation and increase runoff; and third, they interfere with the natural processes that purify water and instead add pollutants like sewage and chemicals to water. 2. What is groundwater mining and what is the danger of this process? Groundwater mining are withdrawals from aquifers exceeding any possibility of recharge. It’s dangerous because in locations, the ground water is dropping and residents may run out of groundwater, at least for irrigation purposes, within a few short years. 3. Why is it possible to run out of freshwater, a renewable resource? Because a new supply is always being produced. But it is possible to run out of freshwater when the available supply runs off instead of entering bodies of freshwater and aquifers or has become so polluted that is not usable.

Human Interference with the carbon cycle (p.501) 1. How are humans increasing the amount of carbon dioxide being deposited in the atmosphere on top of "natural" sources? It’s largely due to the burning of fossil fuels and the destruction of forests to make way for farmland and pasture. When we do away with forests, we reduce a reservoir and also the very organisms that take up excess carbon dioxide. Today, the amount of carbon dioxide released into the atmosphere is about twice the amount that remains in the atmosphere. It’s believed that much of this has been dissolving into the ocean. 2. What are the greenhouse gases and what are the human causes of these gases? The greenhouse gases are carbon dioxide, nitrous oxide, and methane. Carbon Dioxide and also other gases are emitted due to human activities. Nitrous oxide is from fertilizers and animal wastes and methane from bacterial decomposition, particularly in the guts of animals, in sediments, and in flooded rice paddies. 3. Why are these gases called greenhouse gases? Because, just like the panes of a greenhouse, they allow solar radiation to pass through but hinder the escape of infrared rays (heat) back into space. 4. What are some possible dangers of global warming? Possible dangers of global warming are temperatures in polar regions rising to a greater degree than in other regions. If so glaciers will melt and sea levels will rise because water expands as it warms. Water evaporation will increase, there will be an increase in rainfall. Human Interference with the Ozone Shield (p.506) 1. What is the ozone shield and what chemical reaction produces ozone? It’s a layer of ozone that absorbs most of the ultraviolet (UV) rays of the sun so that fewer rays strike the Earth. Ozone forms when ultraviolet radiation from the sun splits oxygen molecules, and then the oxygen atoms combine with other oxygen molecules to produce ozone. 2. What are ozone holes? They are severe depletions of the ozone layer in the popular press. 3. Why are ozone holes dangerous to humans? Because whether or not these holes develop in the spring depends on prevailing winds, weather conditions, and the type of particles in the atmosphere. 4. What human pollution destroys ozone molecules? The human pollution that destroys ozone molecules are chlorine atoms. 5. What are common sources of chlorine pollution? CFC’s being used by humans which are broken down from the chlorine atoms that enter the troposphere and eventually reach the stratosphere primarily. Human Interference and the Arctic (p. 507) 1. What does ANWR stand for and what is it? ANWR stands for Arctic National Wildlife Refuge. It’s a home to a variety of wildlife, such as caribou, migratory birds, grizzly and polar bears, wolves, and musk oxen. 2. Why is ANWR the source of political debate? To conspire to keep oil prices at or near record highs—should the ANWR be opened to oil exploration to help alleviate our dependence on foreign oil and help lower prices? 3. What are the benefits of drilling for oil in ANWR? It has been proposed that a portion of the coastal plain be developed for oil drilling. This action could yield up to a million barrels of oil per day over the next 20 years. Much less disruption to the surface environment would be compared with techniques used in the past. Alaskans would benefit by the creation of new jobs and a boost to the state economy. It would reduce our dependence on foreign oil, and help to buffer us against oil price spikes and supply shocks. 4. What are the risks of drilling for oil in ANWR? It would save even more oil than would be gained by drilling in the ANWR coastal plain. Its contributions to our needs would be relatively minor. The land is located on scattered sites that would need to be connected with roads, increasing the amount of land that would be subject to disruption.