Water and Carbon

• Where are tropical rainforests located?


  Between the tropics (23.5 degrees N/S of the equator, tropic of cancer, tropic of capricorn)
• How many trees in the amazon?

  390 billion
• How large is the amazon?

  5.5 million km2
• How much carbon does the amazon store?

  80-120 billion tonnes
• How much carbon is sunk by rainforest every year?

  7.6GtC/ year
• How has the amazons capacity to absorb carbon changed?

  Peak of taking up 2 billion tonnes of CO2 a year in the 1990s, dropped by 50%
• How has biomass been changing in the amazon?

  Evidence that above ground biomass is increasing by 0.3-0.5% a year.
• How does soil and biomass carbon differ in raniforests?

  Carbon in biomass and soil in rainforests is approximately 50/50, other forests is around 31% biomass and 69% in the soil
• What is a key example of negative feedback regulating the carbon cycle through plant growth?

  More Co2

  Higher temperatures encourages plant growth

  More plant growth means more CO2 is taken up.
• What is an issue with the faster plant growth from higher temperatures?

  Tree live fast and die young, grow faster but have a lower capacity to store carbon and die sooner, releasing carbon.
• How much precipitation in the amazon?

  2000mm/year, can reach 6000mm in some areas
• How much precipitation in the rainforest doesn't reach the ground?

  Up to half, interception storage
• How much precipitation is transpired in the amazon?

  70% transpired, 30% into rivers
• What is the average discharge of the amazon?

  175,000 m3/s
• What is the Rio Negro and how large is it at its mouth?

  Tributary of the Amazon

  100m deep and 14km wide
• What was the rate of deforestation between 2000 and 2007?


  20,000km2/year
• How does Brazil rank in global climate polluters?

  4th - 75% of greenhouse gas emissions from deforestation, burning trees and land use change
• How does slash and burn impact water in trees and soil

  Sudden evaporation of water stored in trees

  Soil is heated up increasing evaporation further

  Reduces soils ability to absorb water, faster drainage, faster erosion, more floods as soil ends up in rivers
• How does slash and burn impact water on a longer term scale?

  Reduced evaporation so less clouds form.
• How is carbon mainly lost after deforestation?

  Through runoff and leaching
• How does deforestation affect local temperature?

  Less transpiration - less clouds - less cloud cover - higher temperatures
• What is the largest cause of deforestation in the amazon?

  Cattle ranching accounts for 80% of deforestation in the amazon
• How does slash and burn affect soil humidity retention?

  Reduces the soils humidity retention up to a depth of one metre
• How does deforestation reduce soil fertility (no slash/burn)

  Removes the litter layer so no transfer of nutrients to soil
• What effect does slash and burn have on rivers?

  Reduces soils ability to absorb moisture - rainfall is drained faster - flashier hydrograph - soil is also eroded as it dries out and is not held by roots, ends up in river beds making them shallower - overall increase risk of flooding
• What is the widescale + long term impact of deforestation on the water cycle?

  - Less trees

  - Less evapotranspiration

  - Less Clouds

  - Less Precipitation

  - Less overland flow

  - Less throughflow
• What is the localised + short term impact of deforestation on the water cycle

  - less vegetation

  - less interception

  - More overland Flow

  - More through flow

  - Less evapotranspiration

  - Same precipitation
• What is the effect on soil of deforestation in the nutrient cycle?

  Litter layer no longer receives organic matter - soil becomes infertile - no vegetation cover to protect soil - nutrients leached rapidly by heavy rain
• What happens to area that have been slashed and burnt?


  The forest will not regrow, new vegetation grows but this stores far less carbon.
• Why does the forest not regrow in slashed and burnt areas?

  Nutrient store has been depleted
• How does deforestation affect global climate change?

  - Carbon released into atmosphere by burning

  - Less carbon dioxide taken up through photosynthesis
• How have rainforest temperatures changed since the 1970s?

  mean increase of 0.26 degrees every ten years.
• What occured in Rio, Reb 2019


  Temperatures spiked over 40 degrees
• how could deforestation make positive feedback in the water cycle?

  - less trees

  - less evapotranspiration

  - less clouds

  - water eaves the system

  - desertification

  - trees die