Case studies

• The Amazon Rainforest covers 40% of South American landmass
• Climate of the Amazon Rainforest

  • Hot
  • Very wet
  • Dense vegetation
• The Amazon Rainforest is home to lots of indigenous people
• Species in the Amazon Rainforest

  • 1 million plant
  • 500 mammal
  • 2000 fish
• Water cycle in the Amazon

  1. Evaporation over Atlantic Ocean

  2. Blown towards the Amazon

  3. Warm temperatures = high evaporation

  4. Dense canopy = high interception

  5. Less water flows into rivers
• Species in the Amazon

  • Adapted to high humidity
  • Frequent precipitation
• Carbon cycle in the Amazon

  • Stores lots of carbon in vegetation and soil
  • A carbon sink
  • Increased productivity due to lots of carbon dioxide for photosynthesis
  • Increases biomass
  • Carbon sequestration has increased
• Trees are growing quicker but dying younger so we may not have a reliable carbon sink in the future
• Deforestation leads to

  No tree canopy to intercept water
• No tree canopy to intercept water

  Water reaches soil and saturates it, increasing surface runoff and increasing flood risk
• Deforestation reduces the rate of evapotranspiration

  Fewer clouds form and rainfall is reduced, increasing drought risk
• Roots don’t hold the soil together

  Heavy rain washes away the nutrients in the soil, transferring carbon to the hydrosphere
• Less leaf litter

  Humus isn’t formed, reducing soil nutrients and limiting absorbed carbon
• Fewer trees

  Means more carbon dioxide emission which increases global warming
• Climate change increases temperature and decreases rainfall


  Leading to drought
• Amazon had severe droughts


  2005 and 2010
• Organisms are adapted to moist conditions so could go extinct with frequent drought
• Drought leads to

  Forest fire, destroying large areas of forests and releasing lots of carbon dioxide
• 4oC temperature rise could kill 85% of the rainforest
• 4oC temperature rise

  Means lots of carbon dioxide is released due to decomposition and there is less photosynthesis
• Selective logging

  • Only some trees are felled
  • Less damaging to the forest than felling all the trees as forest structure is kept and the forest can regenerate
• Replanting

  • New trees are planted to replace the deforested ones
  • Peru planned to restore 3.2 million hectares by 2020
  • Same types of trees planted to keep the variety of trees the same
• Environmental law 

  • Ban use of forest wood from unsustainable forests
  • Ban excessive logging
  • Control land use e.g. Brazilian Forest Code says landowners have to keep 50-80% of their land as forest
• Protection

  • Set up national parks and nature reserves e.g. Central Amazon Conservation Complex protects biodiversity in a 49000km2 area while allowing locals to use forests sustainably
  • Monitoring damaging activities such as logging
• Background for the Amazon

  • Home to 20% of all species on Earth
  • 20% of the Amazon has been deforested
  • Covers 5.3 million km2
  • Brazil is the 4th largest climate polluter and 59% of its emissions are from loss of forest and burning in the Amazon
• Water cycle in the Amazon

  • Average discharge of the Amazon into the Atlantic accounts for 15% of water entering oceans each day
  • Average rainfall of 2300 mm annually but can exceed 6000 mm in some northwest regions
  • Up to half of the rainfall may never reach the ground due to interception by the forest canopy
  • It is then re-evaporated into the atmosphere and 48% of this falls again as rain, further evaporation from rivers and the ground surface and transpiration contribute to the formation of rain clouds
  • 30% of rainfall reaches the sea and the rest of caught up in the precipitation-evaporation closed loop
  • Has global effects as moisture travels around the world
• Deforestation and the water cycle in the Amazon

  • No tree canopy to intercept water so water reaches soil and saturates it, increasing surface runoff and soil erosion and increasing flood risk
  • Reduces the rate of evapotranspiration so fewer clouds form and rainfall is reduced, increasing drought risk
  • Forests emit salts and organic fibres along with water when they transpire which act as condensation nuclei so less clouds are formed
  • Slash and burn techniques reduce the humidity in the soil’s top layer, facilitate sudden evaporation of previously retained moisture in the canopy, increase albedo and temperature and reduce the porosity of soil leading to faster drainage, erosion and river silting which results in floods
  • Evaporation from deforested areas forms shallow cumulus clouds that do not produce rain
• Climate change and the water cycle in the Amazon

  • Flooding due to sea level rise will impact lowland areas such as the Amazon river delta- rate is currently 1-2.5mm per year but this may increase to 5mm/year
  • Sea level rise, increased temperatures and changes in runoff and rainfall will cause changes in species habitats e.g. mangroves
  • Reduced rainfall and increased temperatures can reduce suitable habitats during dry, warm months leading to an increase in invasive, exotic species which outcompete native species
  • Changes in precipitation, extreme rainfall and seasonality may cause an overall reduction in river discharge and flash flooding
• Carbon cycle in the Amazon

  • Estimated store of 80-120 billion tons of carbon
  • Holds 17% of global terrestrial carbon stock
  • Untouched Amazon takes in more carbon than it puts back into the atmosphere and acts as a carbon sink
  • Dead trees emit 1.9 billion tons of carbon dioxide per year while the rainforest absorbs 2.2 billion tons of carbon dioxide
• Deforestation and the carbon cycle in the Amazon

  • Trends of carbon accumulation are decreasing and the rainforest is becoming less efficient at trapping carbon
  • In 1990, it absorbed 2 billion tons and in 2015 it only absorbed 1 billion
  • Around 30% of the anthropogenic carbon emissions come from burning the rainforests alone
  • Forests that experienced disturbances such as logging and fires store 40% less carbon than undisturbed forests
  • Pasturelands contain much less carbon in the upper layer than tropical rainforests
  • When forests are cleared and burned, 30-60% of the carbon is lost to the atmosphere
  • Unburned vegetation decays and is lost within 10 years
  • Soil fungi and bacteria that used to recycle the dead vegetation die off
• Positive feedback cycle between deforestation and wildfires in the Amazon

  • Increased deforestation and climate change in the Amazon
  • Soils and the environment become drier
  • This results in more wildfires in the southeast Amazon
  • Increased atmospheric aerosol loads produced by fires
  • Decrease in droplet size, increased cloud height and cloud lifetime all inhibit rainfall, particularly in the dry season of the southeast Amazon
• Climate change and the carbon cycle in the Amazon

  • Increase in atmospheric carbon dioxide has led to growth in the Amazon’s trees due to increased plant uptake and more sequestration of carbon, creating a negative feedback loop that offsets rising atmospheric carbon dioxide levels
  • In the future, this will cause trees to live faster and die younger leading to a surge in trees dying
  • Climate change can affect species substantially by directly altering the conditions needed to grow and survive
  • Droughts and high temperatures may kill millions of trees
  • A 2oC rise above pre-industrial levels would see 20-40% of the Amazon die off within 100 years, a 3oC rise would see 75% and 4oC would see 85%
• Causes of deforestation in the Amazon

  • Agriculture- forests cleared for soya and palm oil crops, significant conversion to pasture land for cattle grazing
  • Logging operations- timber harvested for construction and furniture, pulp used for paper products, two approaches: selective logging (targeting valuable species such as mahogany) and clear-cutting (removing all trees)
  • Road infrastructure- Brazilian government views roads as essential for Amazon development, Trans Amazonian Highway has already opened large forest areas, BR163 superhighway (1700 km from Cuiabá to Santarem) will make previously untouched forest accessible
  • Mining activities- extensive mineral extraction requiring forest clearance, Brazilian Amazon mines produce iron, manganese, nickel, tin, bauxite, beryllium, copper, lead, tungsten, zinc and gold
• Causes of deforestation in the Amazon

  • Hydroelectric development- 150 new dams planned across the Amazon, Belo Monte dam has been operational since April 2016 and generates 11,000 MW, Sao Luiz do Tapajós will generate 8000 MW but has been delayed due to its impacts on the Munduruku people, dams displace communities, flood forested land, alter hydrology and trap sediment
  • Population growth: migration driven by employment opportunities in extractive industries, mining town of Parauapebas grew from 154,000 people in 2010 to 220,000 in 2012, Brazilian Amazon’s population increased 23% between 2000 and 2010 (11% above the national average), forests are being replaced with rapidly expanding settlements
• Carbon and water interrelationships in the Amazon- forest structure and water recycling

  • Intact forests intercept up to half of the rainfall before it reaches the ground
  • 50-80% of moisture remains within the ecosystem through evapotranspiration
  • Water molecules may be recycled multiple times within the basin
  • Efficient water recycling sustains the carbon-sequestering vegetation
• Carbon and water interrelationships in the Amazon- carbon storage dependent on hydrological patterns

  • Amazon holds approximately 100PgC in above ground biomass
  • Extensive tree coverage enabled by high rainfall allows carbon absorption
  • 182 tree species dominate carbon storage processes (1% of total) and these depend on consistent rainfall patterns
• Carbon and water interrelationships in the Amazon- disruption feedback loops

  • Deforestation reduces evaporation (in Mato Grosso, this has gone from 50km3/year in 2000 to 40km3/year in 2009)
  • Reduced moisture cycling leads to delayed rainy seasons (this was 8 days in Rondonia)
  • Drier conditions increase wildfire risk, releasing 1.9 billion tonnes of stored carbon annually from dead trees
  • Fires produce aerosols that inhibit rainfall, intensifying drought and carbon release- dangerous positive feedback loop where hydrological changes accelerate carbon release
• Carbon and water interrelationships in the Amazon- soil-water-carbon interactions

  • Amazon soils contain 66.9PgC (52% of this in the the top 0.3m layer)
  • Intact forest canopy protects these carbon-rich soils from extreme temperature swings
  • Deforestation exposes soil to drying and erosion
  • Rainfall on exposed soil washes carbon into rivers and accelerates decomposition, turning areas from carbon sinks into carbon sources
• Strategies to reduce climate change in the Amazon- forest conservation and protection

  • Tumucumaque National Park (3.84 million hectares) and Para Rainforest Reserve (15 million hectares)
  • Enrichment of degraded forests using native species
  • Reforestation
  • National and international agreements e.g. the Amazon Cooperation Treaty (ACTO) to prompt harmonious development
• Strategies to reduce climate change in the Amazon- empowering indigenous communities and forest communities

  • Studies show deforestation rates inside indigenous managed forests across the Amazon were 2-3 times lower than outside these areas
  • Supporting indigenous leadership and helping forest communities develop sustainable economic activities like the Brazil nut harvesting in Peru creates incentives for forest protection while improving livelihoods