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GEOGRAPHY CASE STUDY- WATER AND CARBON CYCLES
- Module
- Water and carbon
- Institution
- AQA
including the amazon rainforest, a river catchment (UK), London abstraction cases studies
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AMAZON RAINFORESTBACKGROUND:
Sits within the Amazon River Basin, covering 40% of the S. America continent
Home to 20 million people who use wood, cut down trees for farms and for cattle
Home to 20% of species on earth
CARBON:
100 pgc in above ground biomass in Amazonia
Untouched Amazon forests take in more CO2 than they put back into the atmosphere (carbon
sink)
Dead amazonian trees emit almost 1.9 billion tonnes of carbon to the atmosphere each year
Tropical forests are becoming less efficient at trapping carbon
Although trees grow more quickly, they die younger
Increased C02 necessary for vegetation, increasing productivity and for photosynthesis, thus
biomass increases
WATER:
Rainfall in the amazon basin is about 2300mm annually but only a third is discharged into the
Atlantic
Up to half of rainfall 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
The moisture contributes to the formation of rain clouds which release water back into the
rainforest so 50-80% of moisture remains in the ecosystems water cycle
Moisture created in the amazon ends up falling as rain in Texas and forests in SE. Asia
Deforestation reduces rainfall and moisture leading to drought
A dense canopy means interception is high, so less flows to rivers where there is slower channel
flow
CHANGES TO CYCLES:
Many of these are positive feedback cycles
Deforestation for growing soya or palm oil, involving cutting down trees for timber sale, which is
either selective or clear-cutting
Road building clears trees for development purposes in Brazil, however, if not paved they are
unusable in wetter periods and the government wanted to create a ‘super highway’ from Cuiaba
to Santarem
Mineral extraction clears forests to make mines for extract nickel, iron, tin, copper, lead, zinc, and
gold
Energy development such as hydroelectric power plans to install 150 new dams which create
energy but displace many people and reservoirs create large flood area of land
The power is used for mining which alters the hydrological cycle and trap large quantities of
sediment behind
Bel monte dam generates 11,000 mw of power
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