Chapter 20.2: Impacts on Land


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Grade 8 Integrated Science Chapter 20 Lesson 2 on human impact on the land. This lesson is a detailed look into the positive and negative effects of humans to land biomes. This lesson includes topics such as resource management, the nitrogen cycle, deforestation, mining, agriculture, and urban sprawl. Students should consider the many different impacts we have on the environment everyday.

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Chapter 20.2: Impacts on Land

  1. 1. Chapter 20 Lesson 2 P724-731 IMPACTS ON THE LAND
  2. 2. Vocabulary  Deforestation – the removal of large areas of forests for human purposes  Desertification – the development of desert like conditions due to human activities and/or climate change  Urban Sprawl – the development of land for houses and other buildings near a city  Reforestation – planting trees to replace trees that have been cut or burned down  Reclamation – the process of restoring land disturbed by mining
  3. 3. Using Land Resources  Obtaining resources from nature for books, pens, everything requires people to use land for timber production, agriculture, and mining.  All of these activities impact that environment
  4. 4. Forest Resources  Trees are cut for fuel and to clear land for agriculture, grazing, or building houses or highways  Sometimes large portions of forests are cleared  Deforestation is the removal of large areas of forests for human purposes.  Approximately 130,000km2 of tropical rainforests are cut down each year.  Tropical rain forests are home to an estimated 50% of all the species on Earth.  Deforestation destroys habitats, which can lead to species’ extinction.
  5. 5. Borneo Deforestation
  6. 6. Forest Resources  Deforestation can also affect soil quality.  Plant roots hold soil in place.  Without these natural anchors, soil erodes away.  Deforestation can also affect air quality  Trees remove carbon dioxide from the air when they undergo photosynthesis.  With fewer trees more CO2 remains in the air.
  7. 7. Agriculture and the Nitrogen Cycle  It takes a lot of food to feed 7 billion people  To meet the food demands of the world’s population, farmer often add fertilizers that contain nitrogen to soil to increase crop yield  Living things must use nitrogen to make proteins  When living things die and decompose they release that nitrogen back into the soil and the atmosphere
  8. 8. Agriculture and the Nitrogen Cycle  Although nitrogen gas makes up about 79% if Earth’s atmosphere, most living things cannot use the gaseous form of nitrogen.  Nitrogen must be converted into a usable form.  Bacteria that live on the roots pf certain plants convert atmospheric N into a form useful for plants.  Fertilizers used today contain a abundant amount of Nitrogen in its usable form
  9. 9. Agriculture and the Nitrogen Cycle  Scientists estimate that human activities such as manufacturing and applying fertilizers to crops have double the amount of nitrogen cycling through ecosystems.  Excess nitrogen can kill plants adapted to low nitrogen levels and affect organisms that depend on those plants for food.  Fertilizers can seep into groundwater supplies, polluting drinking water  They can also run off into streams and rivers, affecting aquatic organisms
  10. 10. Other Effects of Agriculture  Soil erosion can occur when land is overfarmed or overgrazed  High rates of soil erosion can lead to desertification  Desertification is the development of desert- like conditions due to human activities and/or climate change  A region of land that undergoes desertification is no longer useful for food production
  11. 11. Mining  Many useful rocks and mineral are removed from the ground by mining  For example, copper is removed from the surface by digging a strip mine.  Coal and other in-ground resources also can be removed by digging underground mines  Mines are essential for obtaining much-needed resources.  However, mines disturb habitats and change the landscape.  Runoff that contains heavy metals can also pollute water sources if not regulated.
  12. 12. Underground Mining
  13. 13. Construction and Development  Land itself is also a very important resource. People use land for living space.
  14. 14. Urban Sprawl  The development of land for houses and other buildings near a city is called urban sprawl  In the 1950s, large tracts of rural land in the US were developed as suburbs, residential areas on the outside edges of a city.  When the suburbs became more crowded, people moved farther out into the country.  Urban sprawl impacts the environment by habitat destruction and loss of valuable farmland  As more ground is paved for sidewalks and streets, runoff increases because rainwater cannot drain into the soil.  Typically runoff from cities and suburbs contain many pollutants, like sediment and chemicals, which can reduce the water quality in streams, rivers, and groundwater
  15. 15. Roadways  Only a small percentage of Americans owned cars before the 1940s.  By 2005, there were 240 million vehicles for 295 million people  In 1960, the U.S. had about 16000km of interstate highways.  In 2012, the interstate high system includes 47000km of paved roadways  This, like urban sprawl, also destroys habitats.
  16. 16. Recreation  People also use land for recreation
  17. 17. Waste Management  Everyday, each person in the U.S. generates about 2.1 kg of trash.  That adds up to 230 million metric tons per year.
  18. 18. Landfills  About 31% of trash in the U.S. is recycled and composted.  About 14% is burned  About 55% is places in landfills where trash is buried  A landfill is carefully designed to meet government regulations.  Trash is covered by soil to keep it from blowing away.  Special liners help prevent pollutants from leaking into soil and groundwater supplies.
  19. 19. Hazardous Waste  Some trash cannot be placed in landfills because it contains harmful substances that can affect soil, air, and water quality.  This trash is called hazardous waste.  The substances in hazardous waste can also affect the health of humans and other living things  Both industries and households produce hazardous waste  Medical hazardous waste includes used needles and bandages  Household hazardous water includes used motor oil and batteries  The EPA (U.S. Environmental Protection Agency) work with state and local agencies to help with safe
  20. 20. Positive Actions  Human actions can have negative effects on the environment, but they can have positive impacts as well  Governments, society, and individuals can work together to reduce the impact of human activities on land resources.
  21. 21. Protecting the Land  Yellowstone National Park was the first national park in the world, establish in 1872.  This set an example to other countries for setting aside land for preservation  State and local governments also followed this example in the U.S.  Protected forests and parks are important habitats for wildlife and are enjoyed by millions of visitors each year  Mining and logging are allowed on some of these lands  However, the removal of resources must meet environmental regulations
  22. 22. Reforestation and Reclamation  A forest is a complex ecosystem,  With careful planning, it can be managed as a renewable resource.  For example, trees can be select-cut  That means that only some trees in one area are cut down, rather than the entire forest.  People also can practice reforestation  Reforestation involves planting trees to replace trees that have been cut or burned down  Reforestation can keep a forest healthy or help reestablish a deforested area.
  23. 23. Reforestation and Reclamation  Mined land also can be made environmentally healthy through reclamation.  Reclamation is the process of restoring land disturbed by mining.  This happens by reshaping the area, covering it with soil, and replanting trees and other vegetation.
  24. 24. Green Spaces  Many cities use green spaces to create natural environments in urban settings.  Green spaces are areas that are left undeveloped or lightly developed.  They include parks within cities and forests around suburbs  Green spaces provide recreational opportunities for people and shelter for wildlife  They also reduce runoff and improve air quality as plants remove excess CO2 from the air
  25. 25. How can you help?  Individuals can have a big-impact on land use issues by practicing the 3-Rs.  Reusing is using an item for a new purpose  Reducing is using fewer resources  Recycling is making new products from a used product  Composting also lessens land impact  You can compost food scraps into a material that is added to soil to increase its fertility  Compost is a mixture of decaying organic matter that improves soil quality by adding nutrients.