4.2 Rainforest

• The rainforest PSD

  Occupies more than 6 million km^2

  70% in Brazil - some in Peru, Ecuador, Venezuela, Bolivia and Colombia
• The rainforest water cycle

  - Dominated by tall, evergreen, hardwood trees

  - High average annual temperatures of 25-30

  - Small seasonal variation in temperature

  - No dry season
• Explain why there are high average temperatures

  - Response to intense isolation throughout the year

  - Significant cloud cover ensures maximum temperature does not reach extremes

  - Seasonal differences in temperature are small and convectional rainfall all year round
• Describe the characteristics of precipitation in the amazon

  - High average annual rainfall >2000m

  - High intensity convectional rainfall intercepted by forest trees are high

  - Intercepted rainfall accounts for 20-25% of evaporation
• Describe the characteristics of evapotranspiration in the amazon

  - High rates due to high temperatures, abundant moisture, and dense vegetation

  - Strong evapotranspiration feedback loops sustain high rainfall levels

  - Half of incoming rainfall is returned to the atmosphere by evapotranspiration

  - Most from intercepted moisture from leaves
• Outline the run off process in the amazon

  - Rapid run off is related to high rainfall, intensive rainfall and well-drained soils
• Identify the atmosphere as a store in the amazon

  High temperatures allow the atmosphere to store large amounts of moisture

  - absolute humidity is high
• Identify how soil and groundwater are a store

  Abundant rainfall and deep tropical soils lead to significant water storage in soils and aquifers
• How does vegetation perform as a store

  Rainforest trees absorb and store water from the soil and release it through transpiration
• Explain the carbon cycle in the rainforest

  - NPP is 2500 grams/m2/year

  - Biomass between 400-700 tonnes/ha

  - Large forest trees 180/tonnes/Cha above ground and 40 tonnes C/ha in roots

  - Absorbs 2.4 million tonnes of carbon a year

  - Warm humid conditions ensure speedy decomposition of dead organic matter and release of CO2

  - Leached acidic soils contain limited carbon and nutrients but also support a biome with the highest NPP of all ecosystems - emphasises the speed of which organic matter is broken down
• Explain how geology affect the water cycle

  - Impermeable catchments (large parts of the basin which are impermeable crystalline rocks) have minimal water storage capacity resulting in rapid run-off

  - Permeable and porous rocks such as limestone and sandstone store rainwater and slow run off
• Explain the affect relief has on the water cycle

  - In gentle areas of relief, water moves across the surface or horizontally through the soil to streams and rivers

  - In the west, the Andes create steep catchments with rapid run off

  - Widespread inundation across extensive floodplains occur annually and store water for several months and slowly release it to rivers
• Describe how temperature affects the water cycle

  - High temperatures result in high rates of evapotranspiration

  - Convection is strong which leads to high atmospheric humidity, development of thunderstorms, and intense precipitation

  - Water is cycled between continually between the land and forest trees and atmosphere by evaporation, transpiration and precipitation
• Determine and explain the physical factors affecting the stores and flows of carbon

  Forest trees :

  - Principle carbon store

  - 100 Billion tonnes of carbon locked in the rainforest

  - Absorbs 2.4 million tonnes a year and releases 1.7 million by decomposition

  - 60% stored above ground in branches, leaves, stems etc, rest in soils

  
  

  Living organisms :

  - Photosynthesis connects rainforest to atmosphere

  - High temperature, high rainfall and intense sunlight stimulate primary production

  
  

  Leaf litter :

  - Accumulates at soil surface and is decomposed quickly by high temperatures by bacteria and fungi

  - Decomposition releases nutrients for the soil for take-up by tree roots which emits CO2 back into the atmosphere

  
  

  Geology :

  - Ancient igneous and metamorphic rock

  - Carbonates are absent
• Outline and describe how deforestation has affected the stores and flows of water

  Deforestation:

  - 17,500 km^2/year from 1970 and 2013

  - Since 1970, almost 1/5 of the rainforest has been destroyed

  - Reduced water storage in forest trees, soils (which have been eroded), permeable rocks (due to more rapid run off) and in the atmosphere

  - Fewer trees mean less evapotranspiration and therefore less precipitation

  - Total runoff speeds have increased, raising flood risks in the basin

  
  

  - Between 2000 and 2012, 30,000 km^2 of Bolivian rainforest was cleared for subsistence farming and cattle ranching on the lower slopes of the Andes which resulted in massive reduction in water storage and accelerated run-off

  - Deforestation has had a huge impact on water cycle and has changed the climate local and regional scales

  - Converting rainforest to grassland increases run off by 27x, half of rainfall goes directly into rivers

  - Rainforest extracts moisture from the soil, intercepting rainfall and releasing it to the the atmosphere through transpiration as well as stabilising forest albedo and ground temperatures

  - Deforestation breaks the convectional rainfall cloud cycle and can lead to permanent climate change

  
  

  - Future deforestation predicts a 20% decline in regional rainfall as the rainforest dries out and turns into grassland

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• Human factors affecting carbon and nutrient flows and stores

  Deforestation:

  - Exhausts carbon biomass store

  - Croplands and pasture contain a small amount of carbon 16.2 tonnes/ha

  - Reduces inputs of organic material to the soil which is depleted of carbon and exposed to strong sunlight, support fewer decomposer organisms which reduces the flow of carbon from the soil to the atmosphere

  
  

  - Calcium, potassium, and magnesium are stored in forest trees

  - Deforestation destroys the main nutrient store and removes nutrients from the ecosystem

  - Nutrients not taken up by the roots are washed out the soils by rainwater and the unprotected plants are quickly eroded
• Explain an indigenous strategy to manage tropical rainforests

  - Indigenous people have lived sustainably in the rainforest for thousands of years, maintaining the water balance, carbon cycle and forest biodiversity

  - Shifting cultivators

  - Contrast : exploitative commercial farming, logging and mining of the past 50 years, indigenous people pursued a way of life adapted to the limited resources and fragility

  
  

  Strategies :

  - Protection through legislation of large expanses of primary forests so far unaffected by commercial developments

  - Projects to reforest areas degraded or destroyed by subsistence farming, cattle ranching, logging and mining

  - Improving agricultural techniques to make permanent cultivation possible

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• Explain the Brazilian government strategy for managing the tropical rainforest

  - Since 1998, the Brazil government has established many forest conservation areas

  - 20x the size of Belgium

  - By 2015, 44% are national parks, wildlife reserves and indigenous reserves where farming is banned

  - Reforestation projects sponsored by NGOs are underway
• Explain how NGOs are managing the rainforest

  Parica Project

  - Western amazon

  - Sustainable forestry scheme aims to develop a 1000 km^2 commercial timber plantation on government owned, deforested land

  - 20 million fast-growing, tropical hardwood seedlings to be planted on 4000 small holdings, to mature over a period of 25 years

  - Financial assistance given to smallholders for land preparation, and maintenance of plots

  - Tree nurseries provide them with seedlings

  - Timber exported along the Amazon and its tributaries
• Evaluate the strategy used by NGOs

  - monoculture and cannot replicate the biodiversity of the primary rainforest

  - sustainable

  - sequesters carbon in the trees and soil

  - reduces CO2 emissions from deforestation

  - re-establishes water and carbon cycles

  - reduces run off and loss of plant nutrients and carbon from the soil
• Describe the strategy used by indigenous Surui people

  - Rondonia

  - Scheme which aims to protect primary rainforest on tribal lands from further illegal logging

  - Reforest areas degraded by deforestation in the past 40 years

  - Plant seedlings bred in local nurseries in deforested areas around villages

  - Native species planted are chosen to provide them with timber for construction, food crops and through logging

  REDD

  2009 - first indigenous group to join Reducing emissions from Deforestation and degradation (REDD)

  - Scheme provides payment vto tribe for protecting the rainforest and abandoning logging

  - Market-based approach involving granting carbon credits to the Surui

  - Credits are purchased by international companies which have exceeded annual carbon emission quotas

  2013 - Natura, a large cosmetics TNC purchased 120,000 tonnes of carbon credits from the Surui - first carbon credit sale by indigenous people
• Explain the methods in which agricultural techniques have been improved

  Farming

  - Main cause of deforestation

  - Low fertility soils meant that cultivation was unsustainable

  - Smallholders abandoned plots which have been turned into low quality grassland

  
  

  1 = diversification

  - Soil fertility being maintained by rotational cropping and combining livestock and arable operations

  - Integrating crops and livestock could allow a fivefold increase in ranching productivity and help slow rates of deforestation

  
  

  2 = dark soils

  - European explorers observed that the Amazon rainforest supported high population densities, and large urban centres

  - contradicted that natural resources are too poor to be settles

  - Human engineered soils: dark soils, made from inputs of charcoal, waste and human manure.

  - Charcoal in the soils attract micro-organisms and fungi and allows the soils to retin their fertility for long-term

  - Scientists are investigating the soils which would allow permanent cultivation which would reduce deforestation and carbon emissions