The Environmental Science Graduate Students at Watlings Castle, San Salvador, Bahamas.(TME 98)This discussion topic submitted by Evelina Maciuleviciute ( maciulevicie@Kenyon.edu) at 8:08 AM on 4/3/02. Additions were last made on Tuesday, April 30, 2002.
A. Introduction and Background
1. Deforestation-- cutting, clearing, and removal of rainforest or related ecosystems, and subsequent conversion into other, less biodiverse, anthropogenic ecosystems such as pasture, cropland, or plantation (Kricher 1997)
2. ex. Costa Rica has over 8,000 species of plants
3. History of deforestation in Costa Rica
a. 1970 cost of oil rose, demand for coffee dropped
B. Causes of deforestation--(Geist and Lambin 2002)
1. Single factors: shifting cultivation and high population growth? NO.
2. Causes: National policies which promote land use, technological drive for mass production, economic drive for agricultural and wood production.
3. Cattle pasture land creation
4. Road construction/development: travel provides access, increases colonization
C. Methods of deforestation
1. Effects of slash burning--(Ellingson et al. 2000):
a. Change in soil nitrogen levels from slash burning:
dramatic short term increase in inorganic nitrogen and surface soil pH levels.
b. Immediately after burning, nitrogen mineralization was higher than in undisturbed plots, but this increase was short term.
2. Effects of logging--(Putz et al. 2001):
a. One of most severe silvicultural interventions (wasteful logging practices)
b. Intensities of logging vary over time
c. Alters composition of landscape, thus influencing its inhabitants
d. Nutrient and hydrolic cycles are affected
e. Trees are not only cut down, mortality rates of nearby damaged trees increases
f. Biogeochemical stocks are changed
3. Forest clearance for cattle ranchers (Park 1992)
a. 2/3 of Costa Rica’s rainforest has been destroyed for cattle ranching
b. Rainforest soil is not suitable for animal grazing or crop production because it quickly loses its fertility
c. Cattle grazing can destroy the physical and chemical structure of the soil in just a few years.
d. Land is cheap, government promotes farming, nutrient-exhausted farms are left behind and the deforestation process is started elsewhere
1. Conservation by collaboration between loggers and environmentalists.
2. Debt-for-Nature-Swap 1987 (Park 1992)
3. Ecotourism brings in more money than wood exports in Costa Rica
4. Sustainable forestry (Park 1992)
5. Sustainable agriculture--Changing from Beef to Dairy Cattle in Costa Rica (Miller and Tangley 1991)
6. Forest reserves--La Amistad Biosphere Reserve, Costa Rica (Miller and Tangley 1991)
7. Growing forest from habitat fragments--ex. Guanacaste National Park, Costa Rica (Miller and Tangley 1991)
E. Long term consequences
1. Increasing atmospheric CO2 levels
2. Change in absorbed levels of radiation
3. Reduction of surface evapotranspiration
4. Warming climate
6. Changing levels of rainfall
a. Keystone species
b. Endemic species
Ellingson, L.J., Kauffman, J.B., Cummings, D.L., Sanford, R.L., Jaramillo, V.J., 2000. Soil N dynamics associated with deforestation, biomass burning, and pasture conversion in a Mexican tropical dry forest. Forest Ecology and Management 137, 41-51.
Geist, H., and Lambin, E., 2002. Proximate Causes and Underlying Driving Forces of Tropical Deforestation. BioScience 52:143-150.
Gradwohl, Judith and Russell Greenberg. Saving the Tropical Forests. London: Earthscan Publications, 1988.
Kricher, John. A Neotropical Companion: An Introduction to the Animals, Plants, & Ecosystems of the New World Tropics. Princeton, NJ: Princeton UP, 1997.
Miller, Kenton and Laura Tangley. Trees of Life: Saving Tropical Forests and their Biological Wealth. Boston, MA: Beacon, 1991.
Park, Chris C. Tropical Rainforests. London: Routledge, 1992.
Putz, Francis, 2001. Tropical Forest Management and Conservation of Biodiversity: an Overview. Conservation Biology 15:7-20.
Zhang, H., Henderson-Sellers, A., and McGuffie K., 2001. The Compounding Effects of Tropical Deforestation and Greenhouse Warming on Climate. Climatic Change 49: 309-338.
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