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Do Now: Movie Clip Answer the following while watching the clip:
1) What causes wild fires? 2) Identify and describe one adaptation of trees to survive fires? 3) How do fires benefit a forest ecosystem?
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Turn and Talk If you lived in an area prone to wildfires, would you want to suppress fires or allow for prescribed burns?
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Aim: Should we control wild fires?
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Read 20: Fighting more forest fires will come back to burn us
Wildfires and climate changedonesia’s recurring forest fires threaten environment Developed vs. developing countries dealing with wild fires.
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Talk 10: Should we control wildfires or let them burn out?
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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
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Natural Capital Degradation: Building Roads into Previously Inaccessible Forests
Figure 10.5: Natural capital degradation. Building roads into previously inaccessible forests is the first step to harvesting timber, but it also paves the way to fragmentation, destruction, and degradation of forest ecosystems. Fig. 10-5, p. 221
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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.
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Selective cutting: middle aged/mature trees are removed individually or in small groups.
Figure 10.6: This diagram illustrates the three 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. 10-6a, p. 222
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Clear-cutting: All trees in an area are removed
Clear-cutting: All trees in an area are removed. Most efficient/most harm. Figure 10.6: This diagram illustrates the three major tree harvesting methods. Question: If you were cutting trees in a forest you owned, which method would you choose and why? Muddy stream Fig. 10-6b, p. 222
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Strip cutting: removes a narrow strip of trees
Cut 1 year ago Uncut Dirt road Cut 3–10 years ago Uncut Figure 10.6: This diagram illustrates the three 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. 222
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Clear-Cut Logging in Washington State
Figure 10.7: This aerial photograph shows the results of clear-cut logging in the U.S. state of Washington. Fig. 10-7, p. 222
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Trade-offs: Advantages and Disadvantages of Clear-Cutting Forests
Figure 10.8: Clear-cutting forests has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Fig. 10-8, p. 223
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FRQ Style: If you were cutting trees In a forest you owned,
(a) Selective cutting (c) Strip cutting Clear stream FRQ Style: (b) Clear-cutting Muddy stream Uncut Cut 1 year ago Dirt road Cut 3–10 years ago Clear stream If you were cutting trees In a forest you owned, Which method would You choose and why? Stepped Art Fig. 10-6, p. 222
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Fires Can Threaten Forest Ecosystems
Forest fires are unique…both good and bad. Fire season: spring-summer Increased in the last 30 years..78 days longer Three types: 1. Surface fires 2. Ground fires 3. Crown fires
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Surface fires Advantages: burns flammable material…prevent major fire
Usually burn leaf litter and undergrowth. Kills seedlings and small trees. Old trees survive. Animals can escape Advantages: burns flammable material…prevent major fire nutrient cycling New vegetation can grow
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Crown fires Extremely hot: burns whole trees Kill wildlife
Increase soil erosion Destroys homes Happens when there have not been surface fires for a long time
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Surface and Crown Fires
B Figure 10.9: Surface fires (left) usually burn only undergrowth and leaf litter on a forest floor. They can help to prevent more destructive crown fires (right) by removing flammable ground material. In fact, carefully controlled surface fires sometimes are deliberately set to prevent the buildup of flammable ground material in forests. Surface fires also recycle nutrients and thus help to maintain the productivity of a variety of forest ecosystems. Question: What is another way in which a surface fire might benefit a forest? Which is a surface fire and a crown fire? Fig. 10-9, p. 223
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Ground Fires Occur underground Burn partially decayed leaves
Common in peat bogs Difficult to detect Hard to extinguish
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Two Methods to Control Fires
Prevention: precautions to minimize possible fires - burning permits - closing parts of forests during fire season, drought, and high tourist season. 2. Prescribed burning: setting surface fires intentionally - thins out underbrush prevents larger fires - careful planning and monitoring - let fires burn out, clear land around fires
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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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Nonnative Insect Species and Disease Organisms in U.S. Forests
Figure 10, Supplement 8
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Group work: Handout
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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 Encouraging news Net total forest cover has stayed the same or increased in U.S. and a few other countries between 2000 and 2007
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Natural Capital Degradation: Harmful Environmental Effects of Deforestation
Figure 10.12: These satellite images show deforestation in Mato Grosso, Brazil, 1992–2006. Fig , p. 226
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Case Study: Many Cleared Forests in the United States Have Grown Back
Forests of the eastern United States decimated between 1620 and 1920 Grown back naturally through secondary ecological succession in the eastern states Biologically simplified tree plantations reduce biodiversity and deplete nutrients from soil
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Tropical Forests are Disappearing Rapidly
Majority of loss since 1950 Africa, Southeast Asia, South America 98% will be gone by 2022 Role of deforestation in species’ extinction Secondary forest can grow back in years
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Natural Capital Degradation: Extreme Tropical Deforestation in Thailand
Figure 10.11: Natural capital degradation. This photo shows extreme tropical deforestation in Chiang Mai, Thailand. Such clearing of trees, which absorb carbon dioxide as they grow, helps to hasten climate change. It also dehydrates the topsoil by exposing it to sunlight. The dry topsoil can then blow away, which can lead to an irreversible ecological tipping point, beyond which a forest cannot grow back in the area. Fig , p. 226
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Species Diversity in Tropical Forests
Figure 10.13: Species diversity: These two species found in tropical forests are part of the earth's biodiversity. On the left is an endangered white ukari in a Brazilian tropical forest. On the right is the world's largest flower, the flesh flower (Rafflesia) growing in a tropical rain forest of West Sumatra, Indonesia. The flower of this leafless plant can be as large 1 meter (4.3 feet) in diameter and weigh 7 kilograms (15 pounds). The plant gives off a smell like rotting meat, presumably to attract the flies and beetles that pollinate the flower. After blossoming once a year for a few weeks, the blood-red flower dissolves into a slimy black mass. Fig , p. 227
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Causes of Tropical Deforestation Are Varied and Complex
Population growth Poverty of subsistence farmers Ranching Lumber Plantation farms: palm oil Begins with building of roads Many forests burned Can tilt tropical forest to tropical savanna
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Major Causes of the Destruction and Degradation of Tropical Forests
Figure 10.14: This diagram illustrates the major underlying and direct causes of the destruction and degradation of tropical forests. Question: If we could eliminate the underlying causes, which if any of the direct causes might automatically be eliminated? Fig , p. 228
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Natural Capital Degradation
Major Causes of the Destruction and Degradation of Tropical Forests Underlying Causes Direct Causes • Not valuing ecological services • Roads • Cattle ranching • Crop and timber exports • Fires • Logging • Government policies • Settler farming • Tree plantations • Poverty • Cash crops • Population growth Cattle ranching Tree plantations Logging Cash crops Settler farming Figure 10.14: This diagram illustrates the major underlying and direct causes of the destruction and degradation of tropical forests. Question: If we could eliminate the underlying causes, which if any of the direct causes might automatically be eliminated? Fires Roads Fig , p. 228
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NATURAL CAPITAL DEGRADATION
• Not valuing ecological services • Government policies • Poverty • Population growth NATURAL CAPITAL DEGRADATION Major Causes of the Destruction and Degradation of Tropical Forests Basic Causes • Crop and timber exports Cattle ranching Tree plantations Logging Cash crops Settler farming Fires Roads Secondary Causes • Roads • Cattle ranching • Fires • Logging • Settler farming • Tree plantations • Cash crops Stepped Art Fig , p. 228
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