Unit 5: Human-Environment Interactions (Lesson 7) Land, Air and Water: Additions and Removals

Transcription

1 Unit 5: Human-Environment Interactions (Lesson 7) Land, Air and Water: Additions and Removals One way geographers classify modifications of the environment is by whether they have an impact on the land, air (atmosphere) or water. Another way of classifying human modifications is by considering whether something was added to or removed from the environment. For instance, when people build a shopping center, they add to land, and when coal is burned, greenhouse gases are added to the air. Humans also remove items from land, air, and water. Cutting down a forest or extracting oil are removing natural resources from the land, and overfishing in Lake Michigan is removing animal species from the water. The cultural landscapes explored in Unit 4 are additional examples of additions to and removals from the land that result in modification of the environment. Can you identify the modifications in the photographs of cultural landscapes below?

2 Significant Modifications Made by Humans Mountaintop Removal Mountaintop removal is a surface mining technique in which explosives are used to remove large areas of mountaintops in order to access underlying coal seams. Read the text selection below to find out more about mountaintop removal. Mountaintop Removal Cuts Through Southern Forests Mountaintop removal has become an increasingly contentious issue over the past several decades, particularly in the southern United States. The U.S. Environmental Protection Agency (EPA) estimated that by the end of 2010, 1.4 million acres of Appalachian forests had been disturbed or cleared by mountaintop removal, an area larger than Delaware. What is Mountaintop Removal? Mountaintop removal is a surface mining technique in which explosives are used to remove large areas of mountaintops in order to access underlying coal seams. Before explosives can be used, however, the land must be cleared of all vegetation, including trees and topsoil. After the vegetation is removed, excess rock, debris, and mining byproducts are pushed into adjacent valleys, where they bury existing streams. Coal companies employ this mining method because it allows for almost complete recovery of coal seams and requires fewer workers than conventional mining. In the United States, mountaintop removal is concentrated in the central Appalachians. This region of the Appalachian Mountains includes southern West Virginia, eastern Kentucky, southwest Virginia, and eastern Tennessee. The area produces 33% of all U.S. coal, 40% of which comes from surface mining. Adapted from: Forest Loss Due to Mining. World Resources Institute. 12 December 2013 < Coal companies use mountaintop removal because it makes it easier to mine coal. Can you understand why some people would be opposed to this kind of coal mining? The modifications made to the environment in mountaintop removal can be classified as both removal and additions to the land. Clearly, removal occurs as large areas of mountaintops are removed in the process. However, the excess rock and debris are pushed into adjacent valleys. This addition to the land changes the surrounding environment as well. Humans could not have done this type of modification two hundred years ago because the equipment and tools needed for mountaintop

3 removal were not available. This is just one example of how technology has accelerated the alteration of the environment by humans. Deforestation The cutting, clearing, and removal of trees in a forest is called deforestation. Sometimes, mountaintop removal can result in deforestation. However, deforestation occurs for other reasons as well. Forests may be cleared to obtain wood for heating or to sell. Most commonly, however, people deforest an area to create more land for farming. Over the past 40 years, as much as 20 percent of the Amazon Rain Forest has been cut down. Pictured below is the state of Rondônia in western Brazil as imaged by NASA s Terra satellite. This 51.4 million acres of forest was once roughly the size of Kansas, according to NASA. It is on track to becoming the most deforested part of the Amazon. The photographs below show the changes humans made in just ten years by deforestation

4 South America isn t the only part of the world where deforestation is a problem. As the map on the right indicates, deforestation has become an issue worldwide. Acid Rain Acid rain is an example of how the environment has been modified through additions to the air. It is caused by the emissions of sulfate and nitrates into the atmosphere from the burning of fossil fuels. The diagrams below will help in understanding how and why acid rain occurs. <

5 < The effects of acid rain include the loss of fish in lakes and streams, damage to forests, the excess growth of algae in water, and deterioration of buildings and monuments. Some scientists believe that there is a relationship between acid rain and increased heart and lung disorders (asthma and bronchitis) in humans. Depletion of the Ozone Layer Ozone is a gas that occurs naturally in the atmosphere several miles above the surface of the earth. This region of the atmosphere is called the ozone layer, and it helps protect life on earth from the sun s harmful ultraviolet rays. Examine the depletion of the ozone layer from 1979 until 2000 in the images below. Note that the purple and blue colors are where there is the least ozone, and the yellows and reds are where there is more ozone. The main cause of the ozone depletion has been found to be gases that contain Cholorofluorocarbons (CFCs),

6 chemicals used for refrigerants and aerosol spray cans. It has been estimated that CFC s have accounted for about 80% of ozone depletion. This is an example of both an addition and a removal in that the addition of CFCs to the atmosphere results in the removal of some of the ozone layer in the atmosphere. What would happen if a hole formed in the ozone and harmful ultraviolet rays were able to pass through? This has actually already happened. Scientists have discovered a hole over the Antarctic and some regions over Chile in South America. In one region under a hole in the ozone, people have experienced an increase in the occurrences of skin cancer and blindness. They also see a huge impact to the plants and animals in their surrounding environment. Moreover, more rays getting through the ozone layer will heat the earth s surface which adds to global warming. Ozone damage is reversible, but it takes decades of reduced emissions. In the figures on the right, the 2010 ozone layer reflects a slow-down in the ozone depletion. This is because CFC s has been banned in some countries including the United States. To view an up-to-date analysis of the ozone layer visit this website: