Case study

• Tropical rainforest in the Amazon:

  Background:

  • 300 billion trees and 15,000 species
  • 20% of all the worlds biomass carbon.
  • 9 countries
  • home to 34 million people who depend on the resources it provides.
• Tropical rainforest in the Amazon:

  Carbon cycle:

  • 76 billion tonnes of carbon
  • increasing in biomass by 0.2-0.5 % per year - carbon sequestration
  • Amazon is a carbon sink, absorbing 600 million tonnes per year
  • trees are growing quicker, they are also dying younger
• Tropical rainforest in the Amazon:

  Water:

  • 15% of all fresh water enters the pacific ocean each day
  • River Negro second largest river in the world of water flow (100m deep & 14km wide)
  • 2,300mm annually. dense canopy so half never reaches the ground as it is intercepted & re-evaporated.
  • lots of evaporation over the Atlantic ocean
  • warm temperatures = high evaporation = increases precipitation
• Tropical rainforest in the Amazon:

  Drivers of change:

  • 2000-2007, deforested at a rate of 20,000 km2 per year
  • Brazil is the worlds fourth largest climate polluter
  • slash and burn techniques; reduces the retention of humidity in the soils top layer
  • erosion increased
  • humidity decrease is 15% less
• Tropical rainforest in the Amazon:

  Climate changes:

  • 0.26 degrees Increase every 10 years
  • severe drought in 2005 and 2010, leading to forest fires
  • more frequent and extreme temperatures
  • plant and animals die in dry weather
  • 4% increase in temperature could kill 85% of rainforest, this would result in carbon being emitted as the dead material decomposes
• Tropical rainforest in the Amazon:

  Vegetation changes:

  • 20% lost and that will rise to 27% by 2030
  • droughts and high temperatures = killing species
  • 2 degrees rise above pre-industrial levels would see 20-40% of the Amazon die off within 200 years
• Tropical rainforest in the Amazon:

  Soil changes:

  • when forests are cleared & burned, 30-60% of the carbon is lost.
  • soil fungi & bacteria that used to recycle the dead vegetation die off.
  • forest clearance = soils exposed to heavy rainfall this rapidly washes away top soil & attacks deep weathered layer below.
• Tropical rainforest in the Amazon:

  river changes:

  changes in the total precipitation, extreme rainfall events and seasonality may:

  • decrease in river discharge
  • changes river biodiversity
  • flash flooding
  • destroy freshwater ecosystems
  • destroy water supply which fulfils the needs of Amazonian peoples
• Tropical rainforest in the Amazon:

  Mitigation:

  • natural parks and forest reserves
  • forest biofuel production could compete with ethanol production from sugar cane by 2030
  • afforestation
  • selective logging
  • agreements: Amazon cooporation to promote harmonious development and Latin american cooperation on watershed management
• River catchment - River Eden

  • december 2015
  • rainfall higher than national average, because of relief. Mountains encourage orographic rainfall, from the irish sea
  • high rainfall = lots of water enters channels in drainage basin = increase flood risk
  • long and narrow which decreases lag time, however as all rivers converge into Carlisle, all water enters city at the same time
  • steep, decreases lag time and increases peak discharge
• River catchment - River Eden

  • highest ground made up of indigenous rock, impermeable increasing surface runoff and decreases lag time
  • lower is made up of limestone and sandstone which is permeable. Infiltration quick so little surface run off, increase lag time. Water in ground storage increases.
• River catchment - River Eden

  factors:

  rainfall - relief rainfall due to, mountains. Soils become saturated. 2800mm annually.

  storms - record rainfall, 262mm in 48 hours

  geology

  drainage basin shape - long and narrow

  relief - steep

  land use - agriculture (compacted soils = decreased infiltration)

  land use - urban areas

  land use - deforestation = decreased interception
• Deforestation in the amazon:

  water cycle

  • in deforested areas no tree canopy to intercept rainfall, so more water reaches the ground surface. soil is too saturated so there is increased surface run off = increased flooding
  • deforestation reduces rate of evapotranspiration, this means less water vapour reaches the atmosphere, fewer clouds form and rainfall is reduced = increased drought
• Deforestation in the amazon:

  carbon cycle

  • without roots to hold the soil together, heavy rainfall washes away nutrients in the top layer of the soil, transferring carbon stored in the biosphere into the hydrosphere
  • deforestation means there is less leaf litter, so humus isnt formed. The soil cannot support much new growth, which limits the amount of carbon that is absorbed
  • trees remove co2 so fewer trees means more co2 in the atmosphere enhancing greenhouse effect and global warming
• Changes in the water cycle - River Eden

  • Farming
  • Construction
  • Deforestation
• Changes in the water cycle - River Eden

  Farming:

  • more intense farming has caused soils to become compacted, reduces infiltration = surface run off is higher. Water levels in rivers rise quickly during heavy rainfall = increase flooding
  • grazing in upland areas so less vegetation = less inerception
• Changes in the water cycle - River Eden

  construction:

  • built up areas have increased
  • impermeable surfaces, which reduces infiltration and greatly increases rate of surface run off flows
  • some new developments have been built on flood plains. This has created flood risk to property and required construction of flood defences. This can cause flooding downstream
• Changes in the water cycle - River Eden

  Deforestation:

  • trees increase Interception and decrease run off so fewer trees mean more run off = greater risk of flooding
• Storm Desmond - river eden

  • December 2015 - caused devastating flooding in Cumbria
  • 262.6mm of rain fell in 48 hours
  • 2000 properties flooded in Carlisle, leaving many homeless