ENVIRONMENTAL SCIENCE

1. 13e ENVIRONMENTALSCIENCE CHAPTER 9:Sustaining Biodiversity: The Ecosystem Approach

2. Wangari Maathai and the Green Belt Movement • Began in Kenya in 1977 • Organizes poor women in rural Kenya • 50,000 members protect forests • Planted 20 million trees • Fruits • Building materials • Firewood • Similar programs in 30 African countries • 2004: Nobel Peace Prize

3. 9-1 What Are Major Threats to Forest Ecosystems? • Concept 9-1 Ecologically valuable forest ecosystems are being cut and burned at unsustainable rates in many parts of the world.

4. Types of Forests • Forests cover 30% of earth’s land surface • Old-growth forests • Second-growth forests • Tree plantation

5. Fig. 9-2, p. 180

6. Fig. 9-3, p. 180

7. Weak trees removed 25 yrs Clear cut 30 yrs 15 yrs Years of growth Seedlings planted 5 yrs 10 yrs Fig. 9-3, p. 180

8. Fig. 9-3, p. 180

9. Fig. 9-4, p. 181

10. Natural Capital Forests Economic Services Ecological Services Support energy flow and chemical cycling Fuelwood Lumber Reduce soil erosion Pulp to make paper Absorb and release water Purify water and air Mining Livestock grazing Influence local and regional climate Store atmospheric carbon Recreation Provide numerous wildlife habitats Jobs Fig. 9-4, p. 181

11. Science Focus: Putting a Price Tag on Nature’s Ecological Services • Estimated value of earth’s ecological services • $33.2 trillion per year • $4.7 trillion per year for forests • Need to start factoring values into land use • Ecological services can be a sustainable source of ecological income

12. Fig. 9-A, p. 181

13. Harvest Methods • Step one: build roads • Erosion • Invasive species • Open up for human invasion • Step two: logging operations • Selective cutting • Clear cutting • Strip cutting

14. Fig. 9-5, p. 182

15. Cleared plots for grazing New highway Highway Cleared plots for agriculture Old growth Fig. 9-5, p. 182

16. Cleared plots for grazing New highway Highway Cleared plots for agriculture Old growth Stepped Art Fig. 9-5, p. 182

17. Fig. 9-6, p. 182

18. (a) Selective cutting Clear stream Fig. 9-6, p. 182

19. Fig. 9-6, p. 182

20. (b) Clear-cutting Muddy stream Fig. 9-6, p. 182

21. Fig. 9-6, p. 182

22. (c) Strip cutting Cut 1 year ago Uncut Dirt road Cut 3–10 years ago Uncut Clear stream Fig. 9-6, p. 182

23. (a) Selective cutting (b) Clear-cutting Clear stream Muddy stream Uncut (c) Strip cutting Cut 1 year ago Dirt road Cut 3–10 years ago Uncut Clear stream Stepped Art Fig. 9-6, p. 182

24. Fig. 9-7, p. 182

25. Forests and Fires • Surface fires • Burn undergrowth only • Cool fire • Ecological benefits • Crown fires • Burn the entire tree • Hot fire • Occur in forests with lack of surface fires

26. Fig. 9-8, p. 183

27. Fig. 9-8, p. 183

28. Loss of Original Forests • Deforestation • 46% in 8,000 years, most since 1950 • Most in tropical areas, developing countries • Estimated loss of 40% intact forests within next 20 years

29. Fig. 9-9, p. 184

30. Fig. 9-10, p. 184

31. Good News on Forests • 2000–2007 net total forested area stabilized or increased • Most of the increase due to tree plantations • Net loss of terrestrial biodiversity

32. Return of Forests in the United States (1) • U.S. forests • Cover ~30% of land • Contain ~80% of wildlife species • Supply ~67% of nation’s surface water • Forest cover greater now than in 1920 • Secondary succession

33. Return of Forests in the United States (2) • Second- and third-growth forests fairly diverse • More wood grown than cut • 40% of forests in National Forest System • Some forests transformed into tree plantations

34. Tropical Forests • Cover 6% of earth’s land area • Habitat for 50% of terrestrial plants and animals • Vulnerable to extinction – specialized niches • Rapid loss of 50,000–170,000 km2 per year • Some second-growth forests

35. Causes of Tropical Forest Deforestation and Degradation • Population growth and poverty • Economic reasons • Logging • Ranching • Farming • Government subsidies • Fires raise temperatures and reduce rainfall

36. Fig. 9-11, p. 186

37. Natural Capital Degradation Major Causes of the Destruction and Degradation of Tropical Forests Basic Causes Secondary Causes • Not valuing ecological services • Crop and timber exports • Government policies • Poverty • Population growth • Roads • Fires • Settler farming • Cash crops • Cattle ranching • Logging • Tree plantations Tree plantations Cattle ranching Logging Cash crops Settler farming Fires Roads Fig. 9-11, p. 186

38. Fig. 9-12, p. 187

39. 9-2 How Should We Manage and Sustain Forests? • Concept 9-2 We can sustain forests by emphasizing the economic value of their ecological services, removing government subsidies that hasten their destruction, protecting old-growth forests, harvesting trees no faster than they are replenished, and planting trees.

40. Fig. 9-13, p. 188

41. Management of Forest Fires (1) • Fire suppression in all types of forests • Increased amounts of underbrush • Increased probability of crown fires

42. Management of Forest Fires (2) • Prescribed fires • Allow some fires to burn • Thin vegetation from forests • Thin around vulnerable homes • Decrease flammability of homes

43. Science Focus: Certifying Sustainably Grown Timber • Forest Steward Council certification of forest operations • Environmentally sound practices • Sustainable yield harvest • Minimal erosion from operations • Retention of dead wood for wildlife habitat

44. Trees and Paper • Many trees are cut for paper production • Alternatives • Pulp from rice straw and agricultural residues (China) • Kenaf (U.S.) • Hemp

45. Fig. 9-14, p. 189

46. Ways to Reduce Tropical Deforestation • Debt-for-nature swaps • Conservation concessions • Gentler logging methods • Encourage use of wood substitutes

47. Fig. 9-15, p. 190

48. Solutions Sustaining Tropical Forests Prevention Restoration Encourage regrowth through secondary succession Protect the most diverse and endangered areas Educate settlers about sustainable agriculture and forestry Subsidize only sustainable forest use Rehabilitate degraded areas Protect forests with debt-for-nature swaps and conservation concessions Certify sustainably grown timber Reduce poverty Concentrate farming and ranching in already-cleared areas Slow population growth Fig. 9-15, p. 190

49. 9-3 How Should We Manage and Sustain Grasslands? • Concept 9-3 We can sustain the productivity of rangeland by controlling the number and distribution of grazing livestock and by restoring degraded grasslands.

50. Grasslands • Provide important ecological services • Second most used and altered ecosystem by humans • 42% grazed by cattle, sheep, and goats – rangeland (open) and pasture (fenced) • Overgrazing