Island Biogeography

2. Island Biogeography • Islands have fewer species than continents • The smaller the island the fewer the species • The farther away from a continent the fewer the species • Theory of island biogeography

4. Island Biogeography • Small islands tend to have fewer habitat types • A small population easily wiped out by a storm, flood, catastrophe or disturbance. • The smaller the pop the greater the risk of extinction • The farther an island is from the mainland the harder it is to reach.

5. Island Biogeography • Islands tend to maintain consistent number of species over time. • Result of the rate at which species added • Minus rate at which they become extinct • Concept applies to ecological islands • A comparatively small habitat separated from a major habitat of some kind.

7. Biogeography and People • People alter biodiversity by • Direct hunting • Directly disturbing habitats • Introducing exotic species into new habitats • Introductions have mixed results • Food sources, landscaping, pets • Disastrous ecological consequences

8. Earth’s Biomes • Rules of moving species • 1st less harmful if moved w/in biotic province • 2nd moving a specie into a new biome from a different biotic province likely to be harmful • 3rd local moves less likely to be harmful than global moves

9. Chapter 13: Forests and Parks

10. Types of Forests • Old-growth forest: uncut or regenerated forest that has not been seriously disturbed for several hundred years. • 22% of world’s forest. • Hosts many species with specialized niches. Figure 10-5

11. Types of Forests • Second-growth forest: a stand of trees resulting from natural secondary succession. • Tree plantation: planted stands of a particular tree species. Figure 10-6

12. Tree Niches • Each species of tree has its own niche and adapted to specific environmental conditions • E.g., water content of the soil • Tolerance of shade • Some adapted to early succession, others to later stages

14. Harvesting Trees • Building roads into previously inaccessible forests paves the way for fragmentation, destruction, and degradation. Figure 10-8

15. Cleared plots for grazing Highway Highway Cleared plots for agriculture Old growth Fig. 10-8, p. 197

16. Harvesting Trees • Trees can be harvested individually from diverse forests (selective cutting), an entire forest can be cut down (clear cutting), or portions of the forest is harvested (e.g. strip cutting). Figure 10-9

17. Natural Capital Forests Ecological Services Economic 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 Provide numerous wildlife habitats Fuelwood Lumber Pulp to make paper Mining Livestock grazing Recreation Jobs Fig. 10-4, p. 193

18. (a) Selective cutting Fig. 10-9a, p. 198

19. (c) Strip cutting Uncut Cut 1 year ago Dirt road Cut 3–10 years ago Uncut Stream Fig. 10-9c, p. 198

20. (b) Clear-cutting Fig. 10-9b, p. 198

23. Effects of Harvesting Trees

24. Trade-Offs Clear-Cutting Forests Advantages Disadvantages Reduces biodiversity Disrupts ecosystem processes Destroys and fragments wildlife habitats Leaves large openings Increases water pollution, flooding, and erosion on steep slopes Eliminates most recreational value Higher timber yields Maximum profits in shortest time Can reforest with fast-growing trees Short time to establish new stand of trees Needs less skill and planning Good for tree species needing full or moderate sunlight Fig. 10-11, p. 198

25. Types and Effects of Forest Fires • Depending on their intensity, fires can benefit or harm forests. • Burn away flammable ground material. • Release valuable mineral nutrients. Figure 10-13

26. Solutions: Controversy Over Fire Management • To reduce fire damage: • Set controlled surface fires. • Allow fires to burn on public lands if they don’t threaten life and property. • Clear small areas around property subject to fire.

27. Solutions: Controversy Over Fire Management • In 2003, U.S. Congress passed the Healthy Forest Restoration Act: • Allows timber companies to cut medium and large trees in 71% of the national forests. • In return, must clear away smaller, more fire-prone trees and underbrush. • Some forest scientists believe this could increase severe fires by removing fire resistant trees and leaving highly flammable slash.

28. Approaches to Forest Management • Managing forests can involve • removing poorly formed and unproductive trees to permit larger trees to grow • Planting genetically controlled seedlings • Controlling pests and diseases • Fertilizing the soil

29. Sustainable Forestry • A sustainable forest is one from which a resource can be harvested at a rate that does not decrease the ability of the forest ecosystem to continue to provide that same rate of harvest indefinitely.

30. What is Sustainability and How is it Applied to Forests • Two basic kinds of ecological sustainability • Sustainability of the harvest of a specific resource w/in an ecosystem (harvest of timber) • Sustainability of the entire ecosystem (forest as an ecosystem) • Lack scientific data to demonstrate that either type ever achieved in forests

31. Solutions Sustainable Forestry • Identify and protect forest areas high in biodiversity • Grow more timber on long rotations • Rely more on selective cutting and strip cutting • Stop clear-cutting on steep slopes • Cease logging of old-growth forests • Prohibit fragmentation of remaining large blocks offorest • Sharply reduce road building into uncut forest areas • Leave most standing dead trees and fallen timber for wildlife habitat and nutrient recycling • Certify timber grown by sustainable methods • Include ecological services of forests in estimating their economic value • Plant tree plantations on deforested and degraded land • Shift government subsidies from harvesting trees to planting trees Fig. 10-12, p. 199

32. A Global Perspective on Forests • Vegetation of any kind can affect the atmosphere in four ways • 1. By changing the color of the surface and therefore the amount of sunlight reflected and absorbed. • 2. By increasing the amount of water transpired and evaporated from the surface to the atmosphere.

33. A Global Perspective on Forests • 3. By changing the rate at which greenhouse gases are released from Earth’s surface into the atmosphere. • 4. By changing “surface roughness”, which affects wind speed at the surface.

35. World Forest Area, Global Production and Consumption of Forest Resources • Countries differ greatly in their forest resources • Potential of their land and climate for tree growth • History of land use and deforestation

37. Forest Area

38. World Forest Area, Global Production and Consumption of Forest Resources • Developed countries account foe 70% of world’s total production and consumption of industrial wood products • Developing countries produce and consume about 90% of wood used as firewood • 90% of world timber trade • Construction, pulp and paper • NA is the dominant supplier

40. World Forest Area, Global Production and Consumption of Forest Resources • In recent years world trade in timber has not grown substantially. • The fundamental questions are • Whether forests can continue to produce at least this amount of timber for an infinite period • Whether they can produce even more as the population grows