THE AMAZON RAINFOREST CASE STUDY

How do the water and carbon cycles operate in contrasting locations

FACTS ABOUT THE AMAZON:

  • Size: 7 million km2

  • Population: 30 million

  • Rivers: Purus, Maranon, Amazon - main river

  • Species: Over 3 million species

  • Vegetation: Over 40,000 species of trees/plants

WHY IS THE AMAZON IMPORTANT?

  • Plays a large part in the water cycle and temperature regulation

  • Exchanges oxygen with CO2 within the atmosphere

  • More than 1 trillion tonnes of CO2 per year are sequestered

WATER AND CARBON CYCLES IN THE TROPICAL RAINFOREST

  • High rates of evaporation - approx. 50% of rainfall is returned by evapotranspiration, mainly from leaf surface

  • Large stores of moisture in the atmosphere, realtive humidity is high

  • Rates of carbon fixation through photosynthesis are high

PHYSICAL FACTORS AFFECTING FLOWS AND STORES OF THE WATER CYCLE

  • Temperature

    • High temps = high rates of evapotranspiration

    • Covection leads to high humidity, storms and intese rainfall

  • Geology

    • Large areas of impermeable rock in the Amazon Basin - lead to high levels of run-off

  • Relief

    • Most of the Amazon Basin has gentle relief

    • Most water movement is by overland flow and throughflow

PHYSICAL FACTORS AFFECLING THE FLOWS OF THE CARBON CYCLE

  • Temperatures

    • High temperatures lead to rapid vegetation growth and large biomass of the Amazon - stores approx. 100 billion tonnes of carbon

  • Vegetation

    • 60% of rainforest carbon is stored in the above-ground biomass trees

  • Organic matter in soils

    • leaf litter and dead organic matter accumulate at soil surface

    • Rapid decompositionand minerals are quickly taken up in the tree root systems

  • Mineral composition of rocks

    • Carbonates are largely absent from the mineral composition of igneous and metamorphic rocks of the Amazon Basin

IMPACTS ON FLOWS AND STORES IN THE DRAINAGE BASIN

  • Deforestation has led to flooding in some areas

  • Deforestation has led to reduced water storage in trees, soils and rocks

  • Fewer trees means less evapotranspiration and precipitation

  • Run-off increases

Impact of deforestation on the water cycle can change climate at local and regional scales, reduced humidity, cloud formation and precipitation, increased peak flows of riveres

IMPACT OF HUMAN ACTIVITY ON CARBON FLOWS, SOIL AND NUTRIENT STORES

  • Deforestation can exhaust the carbon biomass store

  • Deforestation can reduce the input of organic matter to the soil

  • Fewer decomposer organisms mean that the flow of carbon from the soil to the atmosphere is reduced

  • What nurtients remain are quickly eroded by run-off

STRATEGIES TO MANAGE THE TROPICAL RAINFOREST

  • Protection - e.g. Amazon Regional Protected Areas

  • Projects: reforestation projects e.g. Paraic project in Rohdônia

  • Improved argicultural techniques: diversification, rotational cropping and combining livestock and arable farming