Tropical rainforest case study

• Amazon

  Largest tropical rainforest on Earth, sits within the Amazon River basin, covers some 40% of the South American continent, includes parts of 8 South American countries
• Amazon facts

  • Home to 1000 species of bird and 60,000 species of plants
  • 10 million species of insects live in the Amazon
  • Home to 20 million people, who use the wood, cut down trees for farms and for cattle
  • Covers 2.1 million square miles of land
  • Home to almost 20% of species on Earth
  • UK and Ireland would fit into the Amazon 17 times
• The Amazon caught the public's attention in the 1980s when a series of shocking news reports said that an area of rainforest the size of Belgium was being cut down and subsequently burnt every year
• Deforestation has continued to the present day according to the Sao Paulo Space Research Centre
• Current statistics suggest that we have lost 20% of Amazon rainforest
• Carbon

  Tropical forests are very important stores of carbon, and in their untouched state act as carbon sinks
• There are approximately 100 PgC in aboveground biomass (AGB) in Amazonia
• The Amazon forest covers an estimated 5.3 million sq km and holds 17% of the global terrestrial vegetation carbon stock
• Around 1% of all the tree species in the Amazon account for half of the carbon locked in the vast South American rainforest
• Untouched Amazon forests take in more carbon dioxide than they put back into the atmosphere, helping reduce global warming by lowering the planet's greenhouse gas levels
• Dead Amazonian trees (which account for around 20% of above ground biomass) emit an estimated 1.9 billion tons (1.7 billion metric tons) of carbon to the atmosphere each year
• In a normal year, the Amazon rainforest absorbs about 2.2 billion tons (2 billion metric tons) of carbon dioxide
• Untouched tropical forests act as a SINK for carbon
• Amazon forests have acted as a long-term net biomass sink, but also found a long-term decreasing trend of carbon accumulation
• Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s, meaning tropical forests are becoming less efficient at trapping carbon
• Water cycle

  Very active within the Amazon rainforest, interlinks the lithosphere, atmosphere and biosphere
• The Amazon River and its tributaries drain the Amazon basin
• The average discharge of water into the Atlantic Ocean by the Amazon is approximately 175,000 m3 per second, or between 1/5th and 1/6th of the total discharge into the oceans of all of the world's rivers
• The Rio Negro, a tributary of the Amazon, is the second largest river in the world in terms of water flow, and is 100 meters deep and 14 kilometers wide near its mouth at Manaus, Brazil
• Average rainfall across the whole Amazon basin is approximately 2300 mm annually, and in some areas can exceed 6000 mm
• Only around 1/3 of the rain that falls in the Amazon basin is discharged into the Atlantic Ocean
• Up to half of the rainfall in some areas may never reach the ground, being intercepted by the forest and re-evaporated into the atmosphere
• Additional evaporation occurs from ground and river surfaces, or is released into the atmosphere by transpiration from plant leaves
• 50-80 percent of moisture remains in the ecosystem's water cycle in the Amazon
• The moisture created by rainforests travels around the world, with moisture created in the Amazon ending up falling as rain as far away as Texas, and forests in Southeast Asia influencing rain patterns in south eastern Europe and China
• When forests are cut down, less moisture goes into the atmosphere and rainfall declines, sometimes leading to drought
• Causes of deforestation in the Amazon

  • Agriculture (to grow crops like Soya or Palm oil) or for pasture land for cattle grazing
  • Logging - selective or clear cutting
  • Road building
  • Mineral extraction
  • Energy development - hydroelectric dams
  • Settlement & population growth
• The WWF estimates that 27 per cent, more than a quarter, of the Amazon biome will be without trees by 2030 if the current rate of deforestation continues
• Forest losses in the Amazon biome averaged 1.4 million hectares per year between 2001 and 2012, resulting in a total loss of 17.7 million hectares, mostly in Brazil, Peru and Bolivia
• Atmospheric impacts of deforestation


  Deforestation causes important changes in the energy and water balance of the Amazon, with pasturelands and croplands having a higher albedo and decreased water demand, evapotranspiration and canopy interception compared with the forests they replace
• Deforestation in Mato Grosso reduced forest evapotranspiration flux by approximately 1 km3 per year throughout the decade
• Deforestation since the 1970s has caused an 18-day delay in the onset of the rainy season in Rondônia, Brazil
• Fires and drought may create a positive feedback in the SSE Amazon such that drought is more severe with continued deforestation and climate change
• Contribution to climate change


  Tropical forests are very important carbon sinks, but deforestation and degradation are turning these sinks into carbon SOURCES, with around 30% of anthropogenic carbon emissions coming from burning the rainforests alone
• Forests that experienced disturbances such as logging and fires store 40% less carbon than undisturbed forests
• Impacts of climate change on the Amazon

  • Some Amazon species capable of moving fast enough will attempt to find a more suitable environment, many other species will either be unable to move or will have nowhere to go
  • Higher temperatures will impact temperature-dependent species like fish, causing their distribution to change
  • Reduced rainfall and increased temperatures may also reduce suitable habitat during dry, warm months and potentially lead to an increase in invasive, exotic species
  • Less rainfall during the dry months could seriously affect many Amazon rivers and other freshwater systems
  • A more variable climate and more extreme events will also likely mean that Amazon fish populations will more often experience hot temperatures and potentially lethal environmental conditions
  • Flooding associated with sea-level rise will have substantial impacts on lowland areas such as the Amazon River delta
  • Sea-level rise, increased temperature, changes in rainfall and runoff will likely cause major changes in species habitats such as mangrove ecosystems
• Impacts of deforestation on soils

  Removing trees deprives the forest of portions of its canopy, leading to more extreme temperature swings that can be harmful to plants and animals, and causing moist tropical soils to quickly dry out
• Tropical soils contain a lot of carbon, with around 52% of this carbon pool held in the top 0.3 m of the soil, which is most prone to changes upon land use conversion and deforestation
• Deforestation releases much of this soil carbon through clearance and burning, and the remaining carbon is washed away by soil erosion or lost to the atmosphere via decomposition
• Impacts of deforestation on rivers


  Trees help continue the water cycle by returning water vapor to the atmosphere, and when trees are removed this cycle is severely disrupted, leading to increased soil erosion and weathering, flash floods, droughts, more soil and silt being washed into rivers, and disruption of water supplies