unit10 deforestation.ppt
- 1. DEFORESTATION Design by Joe Naumann
- 2. Unit XI. Deforestation and the role of forests in the climate system. A. History of forests Earth 4.6 byr Life >3 byr Multicellular Life 600 myr Plants on land 400 myr (green algae) Ferns, etc. 200 - 70 myr Flowering plants 100 myr (Angiosperrms)
- 3. Unit XI. Deforestation and the role of forests in the climate system. A. History of forests • First land plants short…..<0.5 m (100 myr) • As competition for light increased, they grew taller. Required support (trunks). • Tall forests for ~300 myr, but dramatic changes in composition. • Only last 100 myr would look familiar. Less than 2% of Earth history.
- 4. Unit XI. Deforestation and the role of forests in the climate system. B. Forest types • Boreal Forests (conifers) • Temperate Forests (mixed deciduous hardwoods) • Tropical Rainforests (conifers and hardwoods)
- 5. NPP: Net Primary Productivity What is the net annual production of organic matter by a particular ecosystem,usually measured in the amount of Carbon fixed as organic matter. Net means the total fixed minus the total respired. gC/km2/yr is the (net) grams of carbon fixed over each square kilometer in an average year.
- 6. Characteristics of Earth’s Forests Forest Type Where? Area (km2) Rainfall Soil NPP gC/km2/yr Biodiv- ersity Boreal Temperate Tropical Rainforest High N Latitudes (50-60 °N) Mid- Latitude (30° - 50°) Low Latitude (0 - 30°) 12 M 12 M 17 M Low 20-50 cm/yr Moderate 50 to 100 cm/yr High 2 to 10 m/yr Immature, but abundant minerals yet to be released Rich, fertile, abundant nutrient reserves Poor, highly leached. Most nutrients recycles 300 M 500 M 1000 M Low High Moderate
- 7. Unit XI. Deforestation and the role of forests in the climate system. B. Forest types • Boreal Forests: slow growing, cold, 1/2 year low light, shallow, immature, but mineral-rich soils. Low plant and animal diversity. Capable of sustained harvest, but low yield (slow growth)
- 8. Unit XI. Deforestation and the role of forests in the climate system. B. Forest types • Temperature Forests: Mixed deciduous hardwoods and evergreens, fertile soils. Resistent to disturbance: if cleared, rapid recolonization. Sustained yield OK in most regions.
- 9. Unit XI. Deforestation and the role of forests in the climate system. B. Forest types • Tropical Rainforest: Closed canopy, high rainfall. Most in Brazil (Amazonia), central West Africa (Congo, Zaire), Indonesia and Madigascar. Also Central America, Angola, Peru, Bolivia, India and scattered outliers.
- 14. Unit XI. Deforestation and the role of forests in the climate system. B. Forest types • Tropical Rainforest are the lungs of the world. They inhale CO2 and exhale O2 through the process of photosynthesis.
- 15. Unit XI. Deforestation and the role of forests in the climate system. B. Forest types • Tropical Rainforest: The risky bit….. Soils: Ancient, little rock, highly leached (high rainfall), and few sources of new nutrients. Almost all nutrients are recycled. Incapable of sustained high harvest.
- 17. Unit XI. Deforestation and the role of forests in the climate system. C. Deforestation: why we should be concerned. • Loss of biodiversity • Global warming (burning releases CO2) • Climate impacts
- 18. Unit XI. Deforestation and the role of forests in the climate system. D. The role of forests in the climate system.
- 19. How a geologist views a tree.…Key variables: Leaf area index Rooting depth Water-holding capacity of the soil.
- 20. D. The role of forests in the climate system. Amazonia: Estimated that 50% of the rainfall over the Amazon Basin is recycled water. During a rainfall event, leaves intercept rainwater, and organic-rich soil absorbs rainfall. Leaf evaporation and transpiration returns water vapor to the atmosphere. Two effects: • landward migration of rainfall • water vapor fuels more storms
- 21. D. The role of forests in the climate system. Amazonian Paradox: Amazon rainforest requires heavy rainfall to exist, but half the rainfall is itself depedent on the rainforest being present.
- 22. D. The role of forests in the climate system. Examples: Two adjacent catchments…. One clear cut, the other left forested. Stream runoff in the deforested catchment was 4 to 10 times the forested catchment. Rainfall similar in the two basins, so difference is decreased evapotranspiration.
- 24. D. The role of forests in the climate system. Examples: Ivory Coast: Replacement of rainforest by cropland over last 5 deacdes,; runoff increased 8-fold. Areas formerly suitable for cocoa now abandoned due to lower rainfall, less humidity and more extreme summer temperatures. Similar example in India where rice production fell after rainforest removed.
- 25. D. The role of forests in the climate system. Examples: Ivory Coast, India Proving cause and effect is difficult, but first principles provides a reasonable mechanism to explain these observations.