Learning Unit 4 Tropical Deforestation

1. Learning Unit 4 Tropical Deforestation

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3. Learning Outcomes • Indicate the spatial distribution of the phenomenon of deforestation on a world map • Explain the reasons for the destruction of the tropical rainforests • Discuss the consequences of the destruction of the tropical rainforests • Suggest solutions to decrease deforestation rates • Explain how tropical rainforests can be utilised in a sustainable manner

4. Distribution of deforestation

5. Causes of tropical deforestation Pages 67-69, 471 and 473 in Middleton

6. Causes of tropical deforestation Africa: Cote d’Ivoire • High external debt and declining prices for agricultural exports • Restrictions on the export of logs • Increased log milling and manufacture of wood products • Population growth • Incentives for the production of coffee and cacao

7. Causes of tropical deforestation Latin America: Brazil • Large-scale deforestation began in the mid-1970s. Brazil’s efforts to develop the tropical region included: • Agricultural expansion, including cattle ranchers • Government’s view of the Amazon as an empty land rich in resources encouraged resettlement and migration (‘people without land in a land without people’) • Exploitation of mineral, biotic and hydroelectric resources • Foreign capital investment into oil production • Exports of wheat, soybeans and coffee • Funding from the World Bank for a Highway (BR-364) • Growth and demand for soybeans and beef on international markets prompted further government investment in infrastructure such as railways and highways, accelerating migration and further deforestation

8. Causes of tropical deforestation Asia • Philippines (South Asia): • Poverty and population growth • Elite control over resources and commercial forestry • Creation of secondary forests • Clearing of secondary forests for the expansion of agriculture • Vietnam (South-East Asia): • About 100 million litres of herbicides (including Agent Orange) were sprayed on forests US army during Vietnam War. • About half of Vietnam’s mangrove forests were completely destroyed by aerial spraying of herbicides. • Approximately 22,000km2 of farmland and forest were destroyed by tactical spraying, intensive bombing and mechanical clearance of forest. A further 1170km2 of forest was destroyed by cratering from 13 million tons of bombs

9. Consequences of deforestation Pages 75-81 and 473 in Middleton • Hydrology: • Increase in runoff, stream discharge and the frequency of floods • Increased runoff enhances erosion and sedimentation of rivers • Sedimentation of dams can shorten the time for which they can be used for hydro energy and irrigation • When deep-rooted trees are replaced by shallow-rooted crops or grasses, increased recharge of aquifers can lead to a rise in water tables • Soil degradation (from erosion, landslides, compaction and laterization) is very severe in the tropics • Clearance of vegetation leads to accelerated soil loss • Soil erosion can be exacerbated by compaction caused by heavy machinery, trampling from cattle and exposure to the sun and rain

10. Consequences of deforestation • Biodiversity: • Biodiversity loss • More than half of the number of species on Earth live in tropical forests, thus deforestation in the tropics is a severe threat to the species and genetic diversity on Earth • Less adaptable species such as insects may not survive disturbances to forests • The loss of biodiversity also means a loss of potential sources of new medicines, food crops and genetic material to improve and protect crop yields from diseases and pests • Forest fragmentation can have severe effects on large trees, which are vulnerable to wind turbulence and parasitic vines near forest edges

11. Consequences of deforestation • Biodiversity: • Large tropical forest trees are sources of fruits, flowers and shelter for animal populations • The loss of large trees can diminish the forest volume and complexity, promote the proliferation of pioneer species and alter biogeochemical cycles • Forest degradation and land clearance may also lead to severe consequences from fires • In Vietnam, the spraying of herbicides such as Agent Orange by the US army decreased the abundance of many species and entered the food chain.

12. Consequences of deforestation • Climate: • Local effects: Hotter and drier air over deforested areas lead to decreased cloud formation and precipitation (Guatemala) • Regional effects: Reduction in precipitation and change in surface temperature (Amazonia region) • Global effects: Release of carbon dioxide into the atmosphere, contributing to warming (greenhouse effect) • Indigenous people: • The death or loss of cultural identity of indigenous people in tropical forests