Amazon rainforest Flashcards
Facts about the Amazon rainforest
- worlds largest tropical rainforest
- covers 40% south america
- hot and very wet climate
- very dense vegetation
What are precipitation levels like and why?
- precipitation is very high - mostly exceeds 2000mm per year
- due to high humidity and unstable weather conditions associated with the tropics
- there is high evaporation over the Atlantic Ocean and the moisture-laden air is blown towards the Amazon
- often in the form of torrential downpours
What are evaporation levels like and why?
- warm temperatures means evaporation is high - this increases precipitation
- around 25% of rainfall evaporates
- of the other 75%, half is used by plants and returned to the atmosphere by evapotranspiration, the other half infiltrates into the soil
What is interception like?
the dense canopy can intercept up to 75% of total rainfall - less infiltration into the soil
What is river discharge like?
- average discharge is approximately 175,000m^3/s
- 1/5 of total discharge into oceans of all the worlds rivers
What is the impact of human activity on the water cycle?
- half of the worlds rainforests have already been wiped out to make way for commercial farming, mining, logging and settlements
- atmosphere becomes less humid because evapotranspiration reduced
- fewer trees = decreased interception, compacting the ground and encouraging overland flow
- soil more exposed to sunlight, becomes baked, dry and more vulnerable to erosion
- increased runoff = increased flood risk
How has evapotranspiration changed in Mato Grosso in Brazil?
- in 2000, contributed around 50km^3 per year of evapotranspiration
- however deforestation has reduced forest flux rate by approx 1km^3 per year
- as a result, by 2009 forests were contributing around 40km^3 per year of evapotranspiration
How can deforestation reduce cloud formation?
- forests emit salts and organic fibres when they transpire
- this acts as condensation nuclei and can assist in rain and cloud formation
- their loss inhibits cloud formation and reduces rainfall
How will temperatures change due to deforestation and what will the effect be?
- temperatures will increase by 2-3 degrees by 2050
- a 4 degree increase could kill at least 85% of the rainforest
How much forest was lost between 2000-2010?
3.6m ha per year
How has river discharge changed as a result of deforestation?
20% increased river discharge
What is the amazon carbon cycle like?
- warm and wet climate is ideal for plant growth, promoting photosynthesis which absorbs huge quantities of carbon dioxide from the atmosphere
- plants and trees are a huge carbon store, wood is 50% carbon
- respiration from plants, trees and animals returns carbon dioxide to the atmosphere
- decomposers thrive in the warm and wet conditions which released carbon dioxide into the atmosphere
- carbon stored in the soil
What effect has deforestation had on the rainforest carbon cycle?
- turning carbon sinks into sources
- between 2000-2007, an area of rainforest larger than Greece has been destroyed
How has burning affected the rainforest carbon cycle?
- releases carbon stored in trees back into the atmosphere
- around 30% anthropogenic carbon emissions come from burning
- forests that have experienced disturbances such as logging and burning store 40% less carbon than undisturbed forests
What is the effect of deforestation on stores and flows within the carbon cycle?
- photosynthesis ceases so no carbon dioxide absorbed from atmosphere
- plant and animal respiration drops
- rain washes ash away into the ground increasing carbon content of the soil - this may increase carbon in runoff
- decomposers largely absent from environment
