Amazon rainforest

• Where are tropical rainforests typically located?

  Tropical rainforests are mainly located in the tropics (between the latitudes of 23.5°N the Tropic of Cancer and 23.5°S the Tropic of Capricorn.. Tropical rainforests are found in Central and South America, western and central Africa, western India, Southeast Asia, the island of New Guinea, and Australia.
• Where is the Amazon Rainforest located and what is it size?

  The Amazon Basin is the world's largest rainforest and one of the most biodiverse. Its 300 billion trees and 15,000 species store one-fifth of all the carbon in the planet's biomass.

  Today the Amazon rainforest covers around 5.5 million km2 and is spread across nine countries.

  
• What is the typical climate of the Amazon Rainforest?

  Consistent hot temperatures - typically 25 to 300c

  Small range of temperature - typically 2 or 30c

  High annual rainfall totals - typically over 2000m

  The 'dry' season is very short, and rainfall is normally heavy throughout the year.

  
• How is carbon stored in the Amazon and other tropical rainforests?

  The Amazon is estimated to store between 80 and 120 billion tons of carbon. Along with other tropical rainforests around the globe it forms a carbon sink of 1-3 GtC/year (in other words forests absorbs this much carbon from the atmosphere each year through the process of photosynthesis).

  For other forests approximately 31%ofthecarbonisstoredin thebiomassand 69% in thesoil.

  In tropical rainforests, approximately 50% of the carbon is stored in the biomass and 50% in the soil (IPCC, 2000).
• How is the rate of photosynthesis that occurs at tropical rainforests changing?

  Studies show that forests have been increasing in above ground biomass by 0.3-0.5% per year and the rising productivity of tropical forests is due to biological sequestering of increased CO2 concentrations in the atmosphere (because there is more CO2 in the air, the amount of photosynthesis has increased which has resulted in more plant growth, especially trees).

  
• How is the Amazon's capacity to absorb C02 changing?

  However, a study completed in 2015 has revealed that the Amazon forest is losing its capacity to absorb CO2from the atmosphere. From a peak of two billion tonnes a year in the 1990s, the net uptake of CO2 has dropped by 50%.

  
  

  Furthermore, it appears that the extra atmospheric CO2 (mainly from the burning of fossil fuels) led to a growth spurt for the Amazon's trees.

  However, the growth spurt caused the trees to 'live faster and die younger' and this has led to a surge in the rate of trees dying across the Amazon (when they die, they are decomposed, and carbon is returned to the atmosphere).
• Explain the water cycle in the Amazon Rainforest?

  Average rainfall across the whole Amazon basin is approximately 2,300mm annually (in the north west it can exceed 6,000mm).

  Up to half of this rainfall may never reach the ground. It is intercepted by the forest canopy and re-evaporated into the atmosphere.

  Additional water evaporates form the ground and rivers or is released into the atmosphere by transpiration from plant leaves.

  Only about 30% of the rainfall actually flows out of the Amazon basin through rivers and reaches the sea. The rest is caught up in this constant closed loop.
• What is meant by the water balance?


  The balance between inputs and outputs is known as the water balance or budget.

  The water balance can be shown using the formula:

  precipitation (P) = streamflow (Q) + evapotranspiration (E) +/- changes in storage (S)

  P = Q + E +/- S

  Precipitation (100%) = Streamflow (30%) + Evapotranspiration (70%) +/- changes to stores

  
• What volume of water is discharged from the Amazon?

  The average discharge of water into the Atlantic Ocean by the Amazon is approximately 175,000 m3/s or around 15% of the fresh water entering the oceans each day.

  The Rio Negro, a tributary of the Amazon, is the second largest river in the world in terms of water flow. It is 100m deep and 14km wide near its mouth at Manaus, Brazil.
• What are the main causes of deforestation in tropical rainforests?

  1. Agriculture

  2. Logging

  3. Road building

  4. Mineral extraction

  5. Energy development

  6. Settlement & population growth

  
• At what rate does deforestation occur in the Amazon rainforest?

  Between 2000 and 2007, the Brazilian Amazon was deforested at a rate of approximately 20,000km2/yr. During this time, an area of forest larger than Greece was destroyed.

  Brazil is the world's fourth largest climate polluter, with 75% of their greenhouse gas emissions attributed to deforestation, burning of the trees and land use change.
• What are the impacts of slash and burn techniques on the water cycle?

  It reduces the retention of humidity in the soil's top layer down to a depth of one metre.

  It causes the sudden evaporation of water previously retained in the forest canopy.

  It reduce the ability of the soil to absorb moisture, causing faster drainage of rainfall, more soil erosion and the silting up of rivers and lakes (the eroded soil ends up in rivers and lakes where it settles to the bottom, making them shallower and flooding more likely).
• What are the range of differences between tropical rainforest and pasture land?

  Slash-and-burn agriculture converts forest to farm land, usually pasture land for cattle.

  There are a range of differences between tropical rainforest and pasture land

  Forests absorb approximately 11% more solar radiation.

  Under pasture the average temperature of the soil increases and it stores approximately 15% less moisture compared to soil beneath the rain forest.

  Deeper forest roots draw moisture from deeper under the ground and as this moisture evaporates it increases the humidity and amount of precipitation by up to 20% compared to pasture land.
• What is the impact of localised deforestation on the water cycle?

  
• What is the impact of widescale deforestation on the water cycle?

  
• What is the relationship between forests and carbon dioxide emissions?

  Forests have a life cycle: trees die after a severe fire, setting the stage for new growth. If the forest fully replaces itself, there will be no net carbon change over that life cycle.

  
  

  However, most of the nutrient store in the rainforest lies within the biomass and litter. Rainforest soils contain few nutrients.

  
• What impact does deforestation have on the nutrient store of the rainforest?

  The nutrient cycle in the rainforest is very fragile. If a nutrient flow changes this can have a negative impact on the ecosystem. For example, when deforestation occurs the litter layer no longer receives organic matter and the soil quickly becomes infertile. Because there is no vegetation cover to protect the soil nutrients are rapidly leached by heavy equatorial rainfall.

  
  

  Once the nutrient store has been depleted the forest will not re-grow - the vegetation that replaces it will not store as much carbon as the original forest.
• How does deforestation contribute to global climate change?

  Forests and trees store carbon. When they are degraded or completely cleared, e.g. by fire, this stored carbon is released back into the atmosphere as carbon dioxide

  Through the process of photosynthesis trees convert carbon dioxide into oxygen. Deforestation reduces the capacity of the forest to complete this function.
• What is the impact of climate change on the climate of the rainforest?

  Studies investigating all tropical rainforest regions found a mean temperature increase of between 0.260C every ten years since the mid-1970s and predict that by the year 2050, temperatures in the Amazon will increase by 2-30C. There has also been evidence of more frequent and increased extremes in temperature. For example, in February 2019 temperatures spiked above 400C in Rio de Janeiro and special measures had to be put into place to help keep people and animals cool during the hottest summer in almost a century.Amazonia experienced falling amounts of rainfall between the 1920s and 1970s but since then there appears to have been no significant change.
• What is the impact of climate change on the incidence of droughts in the rainforest?

  There has been a massive net loss of forests in the Amazon Basin, about 3.6 million hectares per year between 2000 and 2010. Although most of this has been caused by deliberate deforestation, a significant amount has been the result of climate. Droughts and unusually high temperatures as experienced in 2005 in the Amazon may also be playing a role in killing millions of trees.A study in 2009 concluded that a 20C temperature rise above pre-industrial levels would see 20-40% of the Amazon rainforest die off within 100 years. A 30C rise would see 75% of the forest destroyed by drought over the following century, whilst a 40C rise would kill 85%.
• Explain the impact of climate change on the soils of the rainforest?

  Amazonian soils contain 4 to 9 Kg/m2 of carbon in the upper 50cm of the soil layer, which pasturelands contain only about 1 kg/m2.When forests are cleared and burned, up to 60% of the carbon is lost to the atmosphere, unburned vegetation decays and is lost within 10 years. The soil fungi and bacteria that used to recycle the dead vegetation die off.
• Explain the impact of climate change on the rivers of the rainforest?

  When forest clearance first occurs, the soils are exposed to the heavy tropical rainfall. Initially this boosts river discharge, however if the deforestation becomes widespread precipitation totals decline and river discharge falls.Soil erosion occurs and silt washes into rivers disrupting river transport and making flooding more likely (as the capacity of the river channel is reduced) The ecology of rivers can change and this has the potential to affect food supply.
• List some agreements and treaties that reduce the effects of environmental change in Amazonia?

  - The Latin American technical Cooperation Network on Watershed Management

  - The Tarapoto process to help achieve harmonious forest development.

  - Amazon Cooperation Treaty Organisation
• List some mitigation strategies that reduce the effects of environmental change in Amazonia?

  - The creation of national parks and forest reserves. E.g. the Tumucumaque National Park (3.84 million hectares) and the Para Rainforest reserve (15 million hectares).

  - Forest biofuel prodiction could compete with ethanol productoon from sugar can by 2030.

  - Reforestation: much of Bazil's industrial timber comes from planted forests which make up only 2% of the forest area.

  - Enrichment of degraded forests using native species.