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Forestry Chapter 10
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What Are the Major Threats to Forest Ecosystems?
Forest ecosystems provide ecological services far greater in value than the value of raw materials obtained from forests. Unsustainable cutting and burning of forests, along with diseases and insects, are the chief threats to forest ecosystems. Tropical deforestation is a potentially catastrophic problem because of the vital ecological services at risk, the high rate of tropical deforestation, and its growing contribution to global warming.
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Forests Vary in Their Make-Up, Age, and Origins
Old-growth or primary forest 36% of world’s forests Second-growth forest 60% of world’s forests Tree plantation, tree farm or commercial forest 4% of world’s forests May supply most of the industrial wood in the future
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Natural Capital: An Old-Growth Forest and an Old-Growth Tropical Forest
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Forests Provide Important Economic and 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
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Forests Provide Important Economic and Ecological Services
Wood for fuel Lumber Pulp to make paper Mining Livestock grazing Recreation Employment
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Estimated Annual Global Economic Values of Ecological Services Provided by Forests
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Unsustainable Logging is a Major Threat to Forest Ecosystems
Increased erosion Sediment runoff into waterways Habitat fragmentation Loss of biodiversity
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Unsustainable Logging is a Major Threat to Forest Ecosystems
Invasion by Nonnative pests Disease Wildlife species Major tree harvesting methods: Selective cutting Clear-cutting Strip cutting
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Major Tree Harvesting Methods
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Figure 10.6 Major tree harvesting methods. Question: If you were cutting trees in a forest you owned, which method would you choose and why? Fig. 10-6a, p. 219
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Figure 10.6 Major tree harvesting methods. Question: If you were cutting trees in a forest you owned, which method would you choose and why? Fig. 10-6b, p. 219
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(c) Strip cutting Uncut Cut 1 year ago Dirt road Cut 3–10 years ago
Figure 10.6 Major tree harvesting methods. Question: If you were cutting trees in a forest you owned, which method would you choose and why? Clear stream Fig. 10-6c, p. 219
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Clear-Cut Logging in Washington State, U.S.
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Trade-offs: Advantages and Disadvantages of Clear-Cutting Forests
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Fire, Insects, and Climate Change Can Threaten Forest Ecosystems
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
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Surface and Crown Fires
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We Can Improve the Management of Forest Fires
The Smokey Bear educational campaign Prescribed fires Allow fires on public lands to burn Protect structures in fire-prone areas Thin forests in fire-prone areas
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Fire, Insects, and Climate Change Can Threaten Forest Ecosystems
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
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U.S. Forest Invading Nonnative Insect Species and Disease Organisms
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We Have Cut Down Almost Half of the World’s Forests
Deforestation Tropical forests Especially in Latin America, Indonesia, and Africa Boreal forests Especially in Alaska, Canada, Scandinavia, and Russia
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Natural Capital Degradation: Harmful Environmental Effects of Deforestation
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Tropical Forests are Disappearing Rapidly
Majority of loss since 1950 Brazil and Indonesia tropical forest loss Role of deforestation in species’ extinction
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Satellite Images of Amazon Deforestation between 1975 and 2001
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Major Causes of the Destruction and Degradation of Tropical Forests
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How Should We Manage and Sustain Forests?
We can sustain forests by emphasizing the economic value of their ecological services, protecting old-growth forests, harvesting trees no faster than they are replenished, and using sustainable substitute resources.
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Solution: Sustainable Forestry
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We Can Improve the Management of Forest Fires
2003 Healthy Forests Restoration Act Pros Cons
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We Can Reduce the Demand for Harvested Trees
Improve the efficiency of wood use Make tree-free paper Kenaf Hemp
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Governments and Individuals Can Act to Reduce Tropical Deforestation
Reduce fuelwood demand Practice small-scale sustainable agriculture and forestry in tropical forest Debt-for-nature swaps Conservation concessions Use gentler logging methods Buy certified lumber and wood products
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Solutions: Sustaining Tropical Forests
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