Biodiversity Part 2
Threats to biodiversity
With a focus on Tropical Rainforest
Starting page 240, Chapter 11
1. Threats to Biodiversity: Habitat Loss
- 80 - 90% of threatened due to HL
- Fragmentation - cutting large into many small
- Road building
- Transmission corridors: oil, gas, electrical
- Activities that lead to HL
- Farming
- Forestry
- Grazing by livestock
- Modification of aquatic habitats
- Conversion to urban & industrial landscapes
2. Causes of Extinction: Figure 11.2
3. Conversion to Agriculture
- 40% of terrestrial surface converted
- Crop land
- Permanent pasture
- Forest & grassland first to be converted
- Vegetation removed
- Exotics move in
- Native grazers replaced by domestic livestock
4. Focus on Tropical Rainforests
5. What are rainforests like?
- Characteristics of a tropical rainforest
- Located between Tropics of Cancer and Capricorn (23oN, 23oS)
- Rainfall > 100 mm /month for 2 out of 3 years (= distributed)
with average 2000> mm rain / year
- No frost with year round temperature: 26 +/- 4oC
- Temperature increases with height and lower vegetation cover
- High humidity: decreases with height in forest
- Variable light: as low as 1% at the forest floor, with
mosaic light gaps
6. How much tropical forest?
- Lowland forests (billion hectares)
- Closed forests
- Tropical Rain forests -- 0.72
- Tropical moist forests -- 0.59
- Open forests
- Tropical dry forests -- 0.24
- Tree plantations -- 0.04
- Upland forests
- Unclassified forests- -- 0.20
7. Changes in Tropical Forests
- Annual Change (deforestation) from 1990 - 2000
- Loss of 14.2 million hectares
- About the size of Iowa in area
- How long will the tropical rainforest last?
- Do the math (rough estimate):
- 1,790,000,000/14,200,000 = about 126 years
- Assuming
- Rate doesn’t change (+ or -)
- Nothing is protected
- Global climate change doesn’t effect
8. Tropical Dry Forest
9. Tree Plantations
- Melina plantation, Limon Province, CR
10: Forests are vertically layered (graphic)
11. Basic structure of a lowland tropical rain forest
- Ground layer
- Sparse due to low light
- Non-vascular plants: mosses, ferns, leaf litter
- Shrub layer: <5 m tall
- Sparse again due to low light
- treelets, prayer plants, heliconias, palms
- Sub-canopy layer: 5-15 m tall
- Palms, trees with large leaves, long spines and high stilt roots
12. Photos: Forest floor
13. Photos: Herbaceous & Shrub Layers
14. Herbaceous & Shrub Layer
15. Epiphytes & Lianas
16. Subcanopy - 1o Palms
17. What is the basic structure of a lowland tropical rain forest?
- Canopy layer: 40 - 55 m tall
- High biodiversity zone
- Supports many epiphytes
- Vines extend from floor to canopy upon trees
- Trees include many in the pea family and palms
- Emergents: lone trees that stick up above the canopy
18. Canopy Trees
19. Buttress & Stilt root Architecture
20. Animals
21. What are the common types of forests in the Tropics?
- Lowland rain forest
- floodplain: swamp forest or Varzea
- Off floodplain: terra firme
- Transitional forest: 500 - 800 m
- Lower Montane: 1000 - 1500 m
- Upper Montane: 1500 - 2500 m
- Paramo: shrubs or bogs, above tree line, 2500 - 4000m
22. Trends:
- As increase elevation, humidity increases and temperature
decreases
- Temperature decreases depend upon humidity
- Dry air: 10 oC/1000 m
- Humid air: 6 oC/1000 m
- PAR (photosynthetically active radiation) and UV increase as
elevation increases
23. Photo: Paramo - High Altitude
24. Photo: Irazu volcano, CR ~ 11,000’
25. Tropical Forest Soils
- Amazonia -
- high rainfall = high leaching
- Soils typically low in organic matter and nutrients
- Nutrients and organic matter tied up into the plants and
animals of the forest
- Remove the plants, remove the productivity
- Costa Rica
- Volcanic soils = recent inputs of nutrients from volcanic ash
- Better soils, more able to recover after deforestation
26. Graphic: How do temperate and tropical soils compare?
27. Deforestation
- Land area in forests has declined by 23% in the last 300 years
- For what did we use this land?
- Wood
- Building
- Fuel wood: 10 energy source for 40% of world
- Agriculture
- Growing crops
- Convert into pasture
- Urban development: housing, roads, businesses
28: Photo: Tropical Land Use: Agriculture
29. Tropical forest destruction
- Land conversion
- Hardwoods (ebony, teak, mahogany) cut
- Forests cleared for cattle ranching
- Costa Rica: 2/3 of deforestation due to L.C.
- Brazil - 1978 - 3,400 mile long Trans Amazon Highway opened the
interior
- Slash-and-Burn: traditional, sustainable
- Large Scale Logging -> Remove the forest - change the climate
- Ethiopian drought and famine linked to forest removal
30. How can cutting trees change the climate?
- Trees pump water into atmosphere: less trees, less rain
- No tree canopy, more evaporation, less reserve, less water
recycling, less rain.
- Less vegetation cover = more erosion when it does rain
- More water export from forest to rivers = less water retained
31. Photo: Slopes converted to pasture, near Lake Arenal, CR
32. Costa Rican Biodiversity is high
33. Why is biodiversity so high?
- Tropical climate: heat and light, lack of freezing
temperatures
- Generally plenty of water
- Large landform diversity: altitude, moisture, oceanic
influence
- Until recently, sparsely populated and inaccessible
34. Map; Costa Rica’s Mountains
35. Graphic: Orographic Precipitation
36. How has Costa Rica Protected its biotic riches?
- Reforestation - planting trees for sustainable forestry
- Creation of parks, preserves and refuges ~ 28% of the country is
protected
- Education & Research - INBio , pharmaceutical research with
Merck, Organization for Tropical Studies