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Do Now: Movie Clip • While watching the clip answer the following: 1) Identify and describe at least 2 causes/impacts of deforestation in the Amazon. Turn and Talk • Why is it important to preserve natural lands and sustain Earth’s biodiversity? Aim: What are the major threats to forest ecosystems? Forests Vary in Their Make-Up, Age, and Origins • • • • Make up 30% of earths land surface. What are the three types of forests? ½ are tropical rain forests. Classified based on their age and structure Old Growth or Primary Forests • Represents 36% of all forested land • • • • Uncut or not disturbed for several hundred years Rich in biodiversity Niches for many animals Top 5: Russia, Canada, Brazil, Indonesia, and Papua New Guinea. Redwood Forest Natural Capital: An Old-Growth Forest Washington State Olympic National Forest Fig. 10-2, p. 219 Second Growth Forest • Represents 60% of forested land • Trees in an area were removed. Ex: clear cutting, forest fires, hurricanes, volcanic erruptions. • Secondary ecological succession: - naturally or when trees are planted Tree Plantation • Tree farm, commercial forest represent 4% of forested land • 1-2 species all the same age. • Violates sustainability and biodiversity • Depletion of nutrients from topsoil • Harvested by clear cutting when trees are commercially valuable. Then replanted. • May supply most industrial wood in the future. • Top 5: China, India, US, Russia, and Canada Rotation Cycle of Cutting and Regrowth of a Monoculture Tree Plantation What are two ways in which this process can degrade an ecosystem? Fig. 10-3, p. 219 Weak trees removed 25 yrs Clear cut 30 yrs 15 yrs Years of growth Seedlings planted 5 yrs 10 yrs Fig. 10-3a, p. 219 Forests Provide Important Ecological Services • Support energy flow and chemical cycling • Reduce soil erosion • Absorb and release water • Purify water and air • Influence local and regional climate • Store atmospheric carbon • Habitats Forests Provide Important Economic Services • Wood for fuel • Lumber • Pulp to make paper • Mining • Livestock grazing • Recreation • Employment • Medicine Natural Capital: Major Ecological and Economic Services Provided by Forests Fig. 10-4, p. 220 Read A Loud • Science Focus: Putting a price tag on natures ecological services. Science Focus: Putting a Price Tag on Nature’s Ecological Services • Forests valued for ecological services • • • • • • Nutrient cycling Climate regulation Erosion control Waste treatment Recreation Raw materials • $4.7 trillion per year Pause…Write…Discuss • Some analysts believe that we should not try to put economic values on the world’s irreplaceable ecological services because their value is infinite? Do you agree with this view? Explain. What is the alternative? Deforestation Step by Step • Step 1: Build roads to access and remove timber • Problems: - Increased erosion - Sediment runoff into waterways - Habitat fragmentation - Loss of biodiversity Natural Capital Degradation: Building Roads into Previously Inaccessible Forests Fig. 10-5, p. 221 Deforestation Step by Step • Step 2: Timber Harvesting; 3 methods • Selective cutting • Clear Cutting: All trees in an area are removed. Most efficient/most harm. • Strip cutting: removes a narrow strip of trees. Selective cutting: middle aged/mature trees are removed individually or in small groups. Clear stream Fig. 10-6a, p. 222 Clear-cutting: All trees in an area are removed. Most efficient/most harm. Muddy stream Fig. 10-6b, p. 222 Strip cutting: removes a narrow strip of trees Uncut Cut 1 year ago Dirt road Cut 3–10 years ago Uncut Clear stream Fig. 10-6c, p. 222 Clear-Cut Logging in Washington State Fig. 10-7, p. 222 Trade-offs: Advantages and Disadvantages of Clear-Cutting Forests Fig. 10-8, p. 223 a) Selective cutting Summary: (b) Clear-cutting Clear stream Muddy stream (c) Strip cutting Uncut Cut 1 year ago Dirt road If you were cutting trees In a forest you owned, Which method would You choose and why? Cut 3–10 years ago Uncut Clear stream Stepped Art Fig. 10-6, p. 222 Fire, Insects, and Climate Change Can Threaten Forest Ecosystems (1) • Surface fires • Usually burn leaf litter and undergrowth • May provide food in the form of vegetation that sprouts after fire • Crown fires • Extremely hot: burns whole trees • Kill wildlife • Increase soil erosion Fire, Insects, and Climate Change Can Threaten Forest Ecosystems (2) • Introduction of foreign diseases and insects • Accidental • Deliberate • Global warming • • • • Rising temperatures Trees more susceptible to diseases and pests Drier forests: more fires More greenhouse gases Surface and Crown Fires Fig. 10-9, p. 223 Nonnative Insect Species and Disease Organisms in U.S. Forests Figure 10, Supplement 8