Summary Amazon Rainforest & Arctic Tundra case studies for OCR A-level Geography (ELSS topic)
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Earth\\\'s Life Support Systems
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OCR A Level Geography Second Edition
Detailed case studies of the Amazon rainforest and Arctic Tundra for OCR A-level Geography, including carbon and water cycle features and metrics, problems and management strategies as well as exam top-tips that I used to achieve an A*
Earth's life support systems case studies (amazon rainforest & arctic tundra)
27 septembre 2023
9 octobre 2023
4
2022/2023
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elss
environmental science
environmental geography
amazon rainforest
water
carbon
management strategies
carbon cycle
water cycle
ocr
a level
geography
arctic tundra
earths 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
tonnes released by decomp./yr, 60% of carbon stored above ground in biomass =
o Dense Vegetation: absorbs & stores water from soil, releases it through
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 Human Factors Affecting Carbon Stores & Flows:
in 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)
rapid run-off BUT limestone near Andes stores rainwater & slow run-off 9 countries ➢ Less cooling effect from transpiration & VOCs = climatic change (global & local
70% of rainforest in Brazil scale) = 20% decline in rainfall predicted = effects forests downwind
2. Relief: mostly extensive lowlands (gentle relief) = water moves by overland
25,000 km2 deforestation/yr ➢ Exhausts carbon biomass store as grasslands store less carbon & have lower inputs:
flow/ throughflow to streams and rivers. West Amazonia = Andes create
Produces 20% of global oxygen 16.3tonnes/ha biomass in rainforest vs 2.7tonnes/ha in soya cultivation
steep catchments with rapid run-off. Widespread inundation across extensive
27°C average temp. ➢ Exposure to sunlight = fewer decomposers = slower rate of carbon return to soil
floodplains (eg: Pantanal) occurs annually, storing water for several months =
slowing movement into rivers
Dynamic, fast moving biome in terms of ➢ Loss of forest cover = bio-spheric carbon is replaced with atmospheric carbon
cycles of water/carbon ➢ Increased drought = increased fire risk for scrublands/grasslands (former forest) =
3. Temperature: High temperatures year-round = high rates of evapotran. World’s largest tract of rainforest with CO2 released by combustion (Eg: 1997 and 1998 El Nino fires)
Strong convection = high atmospheric humidity, development of mostly evergreen, hardwood trees
➢ Woods Hole Research Centre: 400,000km2 of Brazilian Amazon highly vulnerable
thunderstorm clouds & intense precipitation. Water cycled continually Avg. deforestation = 17,500km2/year to fire in 1998 = amplified by worse droughts in 2005 & 2010
between the land surface, forest trees & atmosphere by evapouration, 1970-2013
➢ CO2 emissions from deforestation add ~10% to global warming by reducing
transpiration & precipitation. Almost 1/5 of primary forest
quantity of CO2 pulled by world's forests from atmosphere
destroyed/degraded since 2017
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
, Strategies for Managing the TRF to protect carbon and water cycles
• Deforestation of Amazon is an issue of international & national concern because it has implications on global climate change
• Brazil has committed to restoring 120,000km2 of rainforest by 2030
• Indigenous people have lived sustainably as hunter-gatherers and shifting cultivators for 1000s years in the Amazon
• Exploitative colonial industries (logging/mining/etc) have upset this balance in the last ~50yrs
Protection through legislation of large expanses of primary forest so far unaffected by commercial developments:
• 1998: Amazon Regional Protected Areas established, now covering an area 20x size of Belgium
• 44% of Brazilian Amazon comprised National Parks, wildlife reserves & Indigenous reserves where farming is banned (2015)
Projects to reforest areas degraded or destroyed by subsistence farming, cattle ranching, logging & mining:
• Slow progress as reliant on sponsorship by local authorities, NGOs & businesses
• Eg: Parica project in Rondônia, western Amazon = sustainable forestry scheme aiming to develop 1000km2 (400 smallholdings) commercial timber plantation (20mil fast-growing, tropical hardwood
seedlings) on government-owned, deforested land, over the next 25 years. Financial assistance for preparation, planting & maintenance as well as nurseries are provided. Timber will be exported
along Amazon & tributaries to Manaus or Port Velho. HOWEVER monoculture so cannot replace biodiversity of primary forest BUT still sequesters carbon, reduces CO2 emissions from
deforestation, re-establishes water & carbon cycles, reduces run-off and loss of nutrients
• Eg: Surui Indigenous people's scheme in Rondônia = aims to protect from further illegal logging and reforest areas degraded by deforestation in the past 40yrs. Seedlings of species useful for
food/timber production are planted by tribe members in local nurseries in deforested areas near villages to provide sustainable income. Surui joined UN REDD (Reducing Emissions from
Deforestation and Degradation) scheme in 2009 - first Indigenous group to do so = pays tribe to protect rainforest from logging = grants carbon credits to tribe that can be purchased from them by
international companies that have exceeded their carbon emissions quotas (eg: Natura purchasing 120,000 tonnes of credits from Surui in 2013)
Improved agricultural techniques to make permanent cultivation possible:
• Farming = main source of deforestation in Amazonia but low-fertility soils = unsustainable production = smallholdings eventually converted into low-quality grassland & extensive ranching could
barely support stocking levels of 1 head of cattle/ha
• Diversification: rotational cropping & combining livestock & arable = improved soil fertility, 5x increase in ranching productivity & slowed rates of deforestation
• Human-Engineered soils: colonialists noticed that 'dark soils' with manure, charcoal and waste could support permanent cultivation around urban centres - charcoal attracts micro-organisms & fungi
= allows soils to retain long-term fertility. Recreation of these 'dark soils' are being investigated by scientists
Extension Questions:
1. Why is there a need for management of the Amazon rainforest to maintain the water and carbon cycles?
Capitalist economic system of society demands that the rainforest must be economically productive or there is no incentive to protect it from deforestation. Colonialist managment of the rainforest since
invasion in 1500 has caused water and carbon cycles to become imbalanced, contributing to global warming and reduced resilience of the rainforest. The rainforest must continue to provide a safe and
supportive home for the Indigenous people who have lived on it sustainably for thousands of years
2. How does legislation help sustainable management of the rainforest?
Legal protection for rainforest = a lot harder to carry out illegal activity that harms the rainforest (eg: poaching/logging/farming) PROVIDED incentives are in place to push people towards working with
the forest in legal industries and the policies are enforced. Creates an exemplar framework that different groups can follow to use the rainforest in an economically productive and sustainable way
3. Describe the benefits of reforestation on the Amazon
More trees = less soil erosion and nutrient loss through run-off due to more complex root systems + more evapotranspiration + VOCs = more clouds + rainfall = less variable temperatures and more
rainfall = greater absolute humidity = more stable climatic conditions to support wide diversity of species + more rapid carbon cycling. More trees = more CO2 fixed by photosynthesis = more carbon
sequestered
4. Explain how improved agriculture techniques look to preserve the water and carbon cycle in the Amazon rainforest
Rotational agriculture: using multiple species in rotation, mixing arable/animal farming/using perennials prevents the soil from becoming nutrient-depleted after just a few years & suffering from soil
erosion/leaching = more carbon can be stored in the soil and in plants used around crops such as intercropping with trees. Making low-quality land that has already been deforested more productive
prevents more deforestation from occurring to clear new land = reduced emissions of CO2 and continuation of carbon sequestration. Planting trees = more evapotranspiration + carbon sequestration =
helps to restore tropical rainforest weather conditions in long term
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