Tropical Rainforests and Deforestation

Tropical Rainforests: The Amazon

A. Distribution of the Tropical Rainforest

  • Regions: The Amazon Basin, East Coast of Brazil, Central America, Eastern Madagascar, Central Africa/Congo Basin, Southeast Asia, West Coast of Africa.

B. Climate of Tropical Rainforests

1. Description

  • Equatorial Climate Features:

    • Warm, hot, and humid climate year-round.

    • Average annual temperature: approximately 26 °C.

    • Annual temperature range: very small, around 1 or 2 °C, indicating minimal difference between the warmest and coolest months of the year.

    • Annual precipitation: more than 2,500 mm, with records exceeding 3,000 mm.

    • Throughout the year, even the least humid months receive a minimum of 100 mm of rainfall.

2. Explanation of the Equatorial Climate

  • Factors contributing to warmth and wetness:

    • Latitude: Equatorial location (low latitude) contributes to higher temperatures.

    • Sun Angle: High angle of sun strike increases solar energy absorption.

    • Convectional Rainfall: Band of low pressure leads to convectional rainfall caused by high temperatures.

3. Map Interpretation

  • Examine the distribution map:

    • Patterns observed include locations typically situated near the equator with similar climatic characteristics.

C. Vegetation of the Amazon Rainforest

1. Physical Characteristics

  • Climate:

    • Equatorial climate is warm with average temperatures around 26 °C and abundant humidity.

    • Soil: Thin and poor; however, rich vegetation thrives due to rapid nutrient cycling.

2. Structure of the Amazon

  • Layers:

    • Emergent Layer: Tall trees emerge above the forest canopy.

    • Canopy: Dense layer with most tree growth, where substantial sunlight is captured.

    • Understory: Smaller trees and shrubs with limited light exposure.

    • Forest Floor: Receives minimal sunlight, hosting plants like ferns and seedlings.

3. Adaptations in Vegetation

  • Emergent Layer Trees:

    • May have smaller leaves to counteract stronger sunlight and wind, minimizing water loss.

  • Drip Tips:

    • Leaves with narrow tips that allow rainwater to run off quickly, preventing fungal growth.

    • Examples: Heliconia rostrata.

  • Buttress Roots:

    • Large roots spreading from the base of tall trees to provide stability in nutrient-poor soil.

    • Examples: Tall emergent trees like Brazil nut trees.

  • Lianas:

    • Woody vines that climb trees to reach sunlight.

    • Examples: Orchids and Bromeliads.

4. Nutrient Cycling

  • Input of nutrients through rainfall, loss through runoff, and uptake by plants through decomposing litter from forest floor.

5. Interconnectivity of Elements

  • Alteration of one ecosystem element leads to cascading effects throughout the entire rainforest system.

D. Deforestation in the Amazon

1. Overview of Deforestation

  • Definitions:

    • Deforestation: The process of clearing forested areas for various uses, resulting in loss of biodiversity and changes in climate and soil quality.

2. Human Activities Contributing to Deforestation

  • Uses:

    • Indigenous tribes for food and shelter.

    • Logging for furniture (Mahogany, Teak).

    • Agriculture (cattle and crops) which is significant (~80% of deforestation).

    • Illegal wildlife trade affecting biodiversity.

3. Environmental Impacts

  • Global Warming:

    • Trees absorb CO₂, and their removal increases atmospheric CO₂, contributing to global warming.

    • One mature tree can absorb approximately 22 kg of CO₂ annually.

  • Biodiversity Loss:

    • Loss of habitats leads to species extinction; an estimated 137 species lost every day due to deforestation.

    • Species extinction examples include the Sumatran orangutan and the Javan tiger.

  • Soil Erosion:

    • Tree roots stabilize soil; without them, soil erodes easily which leads to reduced fertility and crop production.

    • Fact: In some tropical areas, deforested land loses up to 100 tonnes of soil per hectare per year.

4. Local Impacts of Deforestation

  • Climate Change:

    • Deforestation disrupts local water cycles, increasing temperatures and leading to droughts.

  • Conflicts:

    • Disputes arise between Indigenous communities and logging companies, often resulting in violence and forced migrations.

5. Social Impacts on Indigenous Communities

  • Loss of Land and Resources:

    • Over 400 Indigenous communities impacted by deforestation, losing food, shelter, and medicinal resources.

  • Cultural Impact:

    • Spiritual and cultural connections lost as sacred sites are destroyed.

6. Pollution Effects

  • Mercury Pollution:

    • Used in gold mining, mercury contaminates rivers and poses health risks to wildlife and humans.

E. Quiz Questions

Part A: Multiple-Choice Questions

  1. Why does deforestation increase global warming?

    • A) Trees produce carbon dioxide.

    • B) Fewer trees absorb carbon dioxide.

  2. What happens to carbon stored in trees when forests are burned?

    • A) It is released into the atmosphere as CO₂.

  3. What does biodiversity mean?

    • A) The variety of plants and animals.

  4. How many species are estimated to be lost every day due to deforestation?

    • C) 137.

  5. The Sumatran orangutan is impacted mainly by:

    • C) Palm oil plantations and forest clearing.

Part B: Short Answer Questions

  1. Explain two ways deforestation contributes to global warming.

  2. Describe how deforestation leads to loss of biodiversity.

  3. Explain how soil erosion happens after trees are removed.

  4. Give two ways deforestation affects Indigenous communities.

Part C: Extension Challenge

  1. "Deforestation causes both environmental and social problems."

    • Provide evidence from the topic.