Highly detailed case study of the carbon and water cycles in the Amazon Rainforest, including the features of these cycles, human and physical factors that impact them, future changes and management strategies
Summary notes OCR A Level Geography Coastal Landscapes
Summary notes OCR A Level Geography Earth's life support systems
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Amazon Rainforest Carbon Cycle:
Amazon Rainforest Water Cycle:
High NPP due to humid equatorial climate: 2500g/m2/yr
Water cycles between basin and Atlantic ocean Biomass carbon store: 400-700 tonnes/ha
20-25% of intercepted rainfall is evapourated Large forest trees store: 180 tonnes carbon/ha above ground, 40 tonnes in roots
Soil carbon stores: 90-200 tonnes/ha
Dense forest canopy intercepts up to 75% of rainfall
2.4bil tonnes of carbon stored/yr overall
50% of non-evapourated water is used by plants and returned by
Limited carbon and nutrient stores in leached & acidic soil BUT speed of recycling
evapotranspiration, remaining water infiltrates into soil & stored/groundwater
allows biome with such a high NPP and biomass to be supported
flow Amazonian rainforest accounts for 15-25% of all NPP in terrestrial ecosystems
50-60% of water recycled by evapotran.
Physical Factors Affecting Carbon Stores & Flows:
Stores & Flows of Water:
1. Forest trees: principal carbon stores, 100bil tonnes locked up in rainforest, 1.7bil
o Dense Vegetation: absorbs & stores water from soil, releases it through tonnes released by decomp./yr, 60% of carbon stored above ground in biomass =
carbon sink of GLOBAL IMPORTANCE
evapouration, high rates of evapotranspiration due to high temps. & high absolute
2. Decomposition: leaf litter & organic matter accumulates temporarily at soil surface
humidity = high precipitation feedback loops. Transpiration water brings
but quickly broken down by decomposers due to warm, humid conditions = emits
dust/minerals into atmosphere with it = aids cloud formation CO2
o Soil/Groundwater: abundant rainfall & deep tropical soils = significant water 3. Geology: limestone acts a significant regional carbon store near the Andes
storage in soils & aquifers
o Run-Off: rapid run-off due to intensive rainfall events & well-drained soils = peak in Human Factors Affecting Carbon Stores & Flows:
river discharge for 1-2 months/yr based on seasonal distribution of rainfall Pollution of water from oil spills = dead organisms = water is unusable for local
o Precipitation: >2000mm average rainfall, no dry season but some months with Key Idea 2a: Case Study of people.
slightly less rain, mostly high-intensity convectional rainfall Tropical Rainforest Amazonia Extraction for residential/industrial purposes = lower water levels = less water
o Atmosphere: high absolute humidity & relative humidity due to high temps. taken up by plants = less evapotranspiration = less clouds + rainfall = area becomes
Fact File: drier
Physical Factors Affecting Stores & Flows of Water: 1 football pitch deforested every minute for farming, infrastructure, hydropower &
6 mil km2 oil exploration
1. Geology: large parts of Amazon basin = ancient shield area with 30mil people Rainforest -> grassland = 27x more run-off & ½ precipitation lost to rivers which
impermeable, crystalline, igneous rocks = minimal water storage capacity = Amazon mainstem, Rio Negro, etc. contains important trace nutrients (Ca/Mg/K)
9 countries Less cooling effect from transpiration & VOCs = climatic change (global & local
rapid run-off BUT limestone near Andes stores rainwater & slow run-off
70% of rainforest in Brazil
2. Relief: mostly extensive lowlands (gentle relief) = water moves by overland scale) = 20% decline in rainfall predicted = effects forests downwind
25,000 km2 deforestation/yr
flow/ throughflow to streams and rivers. West Amazonia = Andes create Exhausts carbon biomass store as grasslands store less carbon & have lower inputs:
Produces 20% of global oxygen
steep catchments with rapid run-off. Widespread inundation across extensive 16.3tonnes/ha biomass in rainforest vs 2.7tonnes/ha in soya cultivation
27°C average temp.
floodplains (eg: Pantanal) occurs annually, storing water for several months =
Exposure to sunlight = fewer decomposers = slower rate of carbon return to soil
Dynamic, fast moving biome in terms of
Loss of forest cover = bio-spheric carbon is replaced with atmospheric carbon
slowing movement into rivers cycles of water/carbon
World’s largest tract of rainforest with
Increased drought = increased fire risk for scrublands/grasslands (former forest) =
3. Temperature: High temperatures year-round = high rates of evapotran.
mostly evergreen, hardwood trees CO2 released by combustion (Eg: 1997 and 1998 El Nino fires)
Strong convection = high atmospheric humidity, development of Woods Hole Research Centre: 400,000km2 of Brazilian Amazon highly vulnerable to
Avg. deforestation = 17,500km2/year
thunderstorm clouds & intense precipitation. Water cycled continually fire in 1998 = amplified by worse droughts in 2005 & 2010
1970-2013
between the land surface, forest trees & atmosphere by evapouration, Almost 1/5 of primary forest CO2 emissions from deforestation add ~10% to global warming by reducing
transpiration & precipitation. destroyed/degraded since 2017 quantity of CO2 pulled by world's forests from atmosphere
Upper Madeira Basin flooding, April 2014
o largest tributary of Amazon River
o 19.68m above normal levels at Porto Velho
o 60 deaths, 68,000 families evacuated, outbreaks of cholera & leptospirosis
o deforestation in Bolivia (2000-2012 = 30,000km2) and Peru = reduced water storage in
vegetation, soils, permeable rocks & atmosphere = increased speed of total runoff
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