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Understanding Deforestation and Its Impact on Ecosystems

This text explores significant changes in ecosystems, with a focus on deforestation methods like slash-and-burn, clear-cutting, and selective cutting. It discusses the negative effects, including increased soil erosion, habitat loss, and nutrient runoff leading to algae growth. Additionally, it highlights the role of fire in maintaining ecosystem diversity, the transition from oligotrophic to eutrophic lakes, and the impacts of water pollution. The text also covers the effects of cottage dwellers on Alberta lakes, emphasizing the consequences of human activities on water quality and biodiversity.

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Understanding Deforestation and Its Impact on Ecosystems

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  1. 4.5 Changes in Ecosystems pgs. 113 - 121

  2. Deforestation • Slash and Burn – the complete clearing of a forest by felling and burning the trees

  3. Deforestation • Clear cutting – the removal of all trees in an area

  4. Deforestation • Selective cutting – the harvesting of only certain trees from an area

  5. Negative Effects • Soil erosion and runoff into streams increases • Nitrates and other nutrients are carried into streams and ponds, increasing algae growth • Loss of habitat • Replanting can take 80-90 years before trees are large enough to harvest More details can be found on pg 114

  6. Fire • Fire is an important and often helpful cause of change in an ecosystem

  7. Effects of Fire • Creates and maintains a variety of different vegetation types • Essential in the germination of certain seeds • Allows for new growth in an old growth forest

  8. Questions pg. 115 • Do Practice Questions 1-3

  9. Changes in Lake Ecosystems • Oligotrophic Lakes – deep, cold and low in nutrient levels • Eutrophic Lakes – generally shallow, warmer and high in nutrient levels • Eutrophication – the evolution from an oligotrophic lake to an eutrophic lake

  10. Oligotrophic Lake

  11. Mesotrophic Lake

  12. Eutrophic Lake

  13. Water Pollution • Human waste • Fertilizers • Household and industrial products • Thermal energy (heated water) • Water pollution is any physical or chemical change in surface water or ground water that can harm living things • See pg 116 for details

  14. Indicators of Water Quality • Detection of coliform bacteria (naturally occurring bacteria found in the intestines of humans and animals) would also indicate the likelihood of other disease causing bacteria

  15. Biological Oxygen Demand (BOD) • BOD – a measure of the amount of dissolved oxygen needed by decomposers (bacteria) to break down organic matter in a sample of water at 20 C over 5 days • As the number of organisms increases, so does the BOD High numbers of organisms = High BOD High numbers of organisms = Less dissolved oxygen

  16. Question pg. 118 • Do Practice Question #5 and 6

  17. Changes in Alberta Lakes • Watershed – the land that drains toward a lake or other body of water

  18. Effects of Cottage Dwellers on Alberta Lakes

  19. Making sandy beaches increases erosion • Planting lawns increases nitrogen and phosphorus runoff from fertilizers • Removing shoreline plants takes away a filtering system for harmful chemicals moving from the land to the lake, decreases shade and thus affects water temperatures near the shore • Human sewage seeping from outhouses cause increased bacteria activity (less oxygen)

  20. Human sewage seeping from outhouses cause increased bacteria activity (less oxygen)

  21. Questions • Do Practice Questions pg. 120 #7 and 8

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