tropical rainforests

• The Amazon Rainforest

  Largest rainforest in the world, covering 670 million hectares and 9 countries in South America

  
• 20% of the Amazon Rainforest has already been lost and 200,000 acres are burned everyday
• Factors contributing to deforestation in the Amazon

  • Agriculture
  • Urbanisation
  • Mining

  
• The Amazon Rainforest

  • One of the most biodiverse rainforests in the world, including 300 billion trees and 15000 species
  • Home to 34 million people who depend on its resources such as food and wood for fuel

  
• ⅕ of the world's carbon is stored in the biospheric store (trees and vegetation)
• Soil nutrient levels in the Amazon

  • Poor quality
  • Low concentrations of nutrients such as carbon, nitrogen, potassium and phosphorus
  • High rainfall may dislodge and erode the soil and the fast uptake of the nutrients from decomposing organic matter by plants

  
• Ecological features


  Abiotic and biotic factors in an environment which are specific to support different species
• Being adapted to relatively stable conditions makes species vulnerable to changes in the environment which can move them out of their range of tolerance
• Ecological features of the Amazon

  • High light levels allow high photosynthesis rates to support a rich food web
  • Constant warm temperatures and regular high rainfall allow plants to grow throughout the year without seasonal changes

  
• Importance of the Amazon Rainforest

  • Biodiversity - contains around half of all existing plant and animal species in the world
  • Medicines - Hundreds of rainforest plants are used in modern medicines, 25% of all medicines come from rainforest plants
  • Food - 80% of the world's diet originated from rainforest plants

  
• Carbon sequestration


  The process where trees absorb atmospheric carbon dioxide, release oxygen and lock up carbon until the tree dies, decays or is burnt

  
• One hectare of rainforest can store over 200 tonnes of carbon, equivalent to 100 hectares of grassland

  
• Transpiration


  The process where tropical rainforests add water to the atmosphere

  
• Soil conservation

  Rainforests regulate water flow and prevent flooding and erosion

  
• People in the rainforest

  • About 1,000 indigenous tribes
  • Millions of indigenous people depend on rainforests for their survival
  • Over a billion make their livelihoods from its products
• Fuelwood collection


  Wood is cut down from the tropical rainforests and is burned as an energy resource, particularly in rural areas of low income countries
• The rate of deforestation is higher than the rate of growth of new plantations, wiping away ecosystems and biodiversity

  
• Deforestation reached a peak of 27000 in 2004 but decreased in 2013 due to improved law enforcement by a satellite based forest monitoring system

  
• Subsistence agriculture


  Methods such as 'slash and burn' and 'shifting field' to clear areas of the forest, but with increasing populations the time between an area being abandoned and recolonised has reduced causing environmental problems and soil degradation
• Commercial agriculture


  Increasing demand for farmland is destroying habitats through clearance, and farming crops and cattle is unsustainable as tropical soils become infertile and there will be a reduction in crop yields making it difficult for the rainforest to recolonise
• Impacts of climate change on the rainforest

  • Temperature increase directly affects species
  • Caused by wildfires, droughts or decrease in rainfall reducing water availability
  • Populations of many frogs and toads in cloud rainforest are declining as the drier climate is reducing condensation and cloud cover
  • Computer models predict rainforest areas will be replaced by Savannah Grasslands in the future

  
• Conservation efforts


  • Reducing debt - debt for nature swaps where debt is cancelled in exchange for preserving the rainforest
  • Establishing protected areas - e.g. Rio Bravo Conservation and Management area in Belize
  • Conservation legislation - e.g. International Tropical Timber Agreement to promote sustainable timber trade
  • Selective logging - removing selective trees based on criteria to allow others to grow