rainforests

• Tropical rainforests (equatorial climate):

  • Found on or near the equator.

  The main concentrations are:

  • The Congo Basin in central and west Africa.
  • The Amazon in Brazil, Peru, Bolivia and Ecuador.
  • SE Asia.
  • Madagascar.
  • North east Australia.
  • Southern India and Sri Lanka.
  • Central America.
• Temperature:

  • LATITUDE: between Tropic of Cancer and Tropic of Capricorn.
  • DISTANCE FROM THE SEA: places near the sea are cooler in the summer, and places near the sea are warmer in the winter.
  • PREVAILING WINDS: if prevailing wind is from the poles, temp will be lower. But if prevailing wind is from the tropics then temp will be higher.
  • OCEAN CURRENTS: hot ocean currents tend to warm winters and cold ones cool summers.
  • ALTITUDE: temp on average decrease 1°C for every 100m gained.
  • ASPECT: the direction that something faces.
• CS: Manaus, Amazon Rainforest, Brazil:

  Description:

  • Hot and wet, high rainfall and temperature.
  • High temperature through the year/no seasons.
  • Average temp around 30 °C - Manaus temp never below 26 °C.
  • 2000mm of rain or more a year, Manaus in March 340mm of rainfall.
  • High rainfall all year.
  • High humidity.
  • High angle of sunlight.
• CS: Manaus, Amazon Rainforest, Brazil:

  Explanation:

  • High angle of sun/direct sunlight/sun's rays are concentrated.
  • Build up of cumulus clouds.
  • High annual rainfall total - Equator in low pressure area, so air rises causing daily convectional rainfall.
  • High temps mean rapid evaporation so rising air is moist ond brings heavy rain as it condenses.
  • Dense vegetation and high temps also mean rapid transpiration which increases rainfall.
  • Daily cloud cover insulates and prevents heat escaping at night.
• CS: Benefits of TRF, Amazon Rainforest:

  • Tribes like Erigbaagtsa provide food for themselves by hunting. 200,000 people consider the Amazon their home.
  • Rubber tapping - near Amazon river and latex is exported from Manaus.
  • Species of hardwoods e.g. mahogany are logged which provides jobs for people in Amazon and wood for a global market.
  • Natural habitat for 100s of plant/animal species e.g. Pythons etc. This attracts tourists and croates jobs locally.
• CS: Benefits of TRF, Amazon Rainforest:

  • Plants like the Rose Periwinkle, increased the survival rates of children with leukaemia.
  • 25% of medicine uses plants from the Amazon.
  • Cash crops/agriculture: coffee, mango, banana.
• Hadley Cell:

  • Because of hot temp near the equator, the land warms the air above which begins to rise.
  • As it rises it's pushed out towards the tropics where it begins to cool and slowly sink.
  • The sinking air then returns towards the equator where there is low pressure.
  • The rising air causes convectional rain near the equator. However, because of the rain over the equator, the air reaching the tropics is very dry creating arid desert like conditions.
• CS: Causes of Deforestation, Amazon Rainforest, Brazil:

  • Trees are cleared to rear cattle, and farmer's plant grass to feed the cattle.
  • Companies such as Clarks, Nike, Adidas, and Timberland until very recently used leather from cattle reared in the Amazon to make their shoes.
  • Deforestation occurs because there are minerals in rainforest areas. In some places hydroelectric power stations are made to provide electricity for local people.
  • Farmers make more profit by rearing cattle in the rainforest as it is cheap to do so as the land is cheap.
• CS: Causes of Deforestation, Amazon Rainforest, Brazil:

  • Dams provide over 90% of Brazil's electricity.
  • Large areas of land are cleared to make roads through the rainforest. For example, the Trans - Amazonian Highway.
  • Roads are built through the Amazon to transport materials, such as timber, to be sold.
• Impacts of deforestation on local environment:

  • It kills animals.
  • Reduces variety of species.
  • Loss of habitat for animals.
  • Threatening species with extinction.
  • Reduces interception of rainfall.
  • Increasing run off causing floods.
  • Animals scared/run away/killed.
• Global impacts on natural environment:

  • Release of CO2 (as a result of burning).
  • Trees are no longer available to convert CO2 to O2.
  • Carbon dioxide traps heat.
  • Increases greenhouse effect.
  • Melting of ice caps.
• Soil erosion:

  • Trees protect the soil.
  • Roots of plants no longer hold the soil in place.
  • Less interception so more surface run off and floods.
  • Surface becomes compacted by heavy rain/bulldozers.
  • More exposed to the wind erosion.
• Developing TRF sustainability:

  • Selective logging - only cut at a certain height, allows young trees guaranteed life span.
  • Helilogging - lifting tree from sky, no need for roads etc.
  • Rubber tapping - trees keep growing.
  • Tribal reserves; educates people.
  • Ecotourism.
  • Replanting trees.
• Nutrients used in a TRF:

  • Leaves fall to ground.
  • Turned into humus/decompose.
  • Humus mixed with soil.
  • Nutrients returned to plants/taken up by roots.
• Why is reducing deforestation difficult for LEDCs?

  • A source of income for LEDCs.
  • Trees used for furniture/building/construction.
  • Many areas are too large to patrol e.g. Amazon.
  • Pressure on land for food plantations.
  • Lack of and weak government laws.
  • Need trees for cooking/fuel.
• Types of farming:

  • HUNTER GATHERING: hunting wild animals and collecting (gathering) of wild fruits and nuts.
  • SHIFTING CULTIVATION: deforesting one area, growing crops in it for a number of years until the ground become infertile and then moving onto a new area.
  • SLASH AND BURN FARMING: burning down an area of the TRF to make way for farming. It clears an area quickly and the ash fertilises the soil.
  • FALLOW PERIODS: not using the land for a while. The aim is for the soil to regain some of its fertility. Shifting cultivators may return to these areas.
• Main features of natural vegetation:

  • Hundreds of different species/large biodiversity. e.g. mahogany.
  • Evergreen - stays green all year around as no cold season.
  • Different layers of vegetation.
  • Canopy of trees.
  • Shrub layer.
  • Emergent/tall trees.
  • Drip tip leaves.
• Structure:

  • The emergent layer (38m)
  • The canopy (29m)
  • The understory (17m)
  • The forest floor (5m)
• Animals:

  • Tree sloth.
  • Boa constrictor.
  • Grasshoppers.
  • Spider monkays.
  • Toucans.
• Lianas: Vines that have a woody stem and a fleshy root.
• Emergents: Trees grow tall and straight above the canopy layer. Helps them get as much sunlight as they con.
• Epiphyte: A plant that grows on another plant as they have no roots, usually a tree, as they have no roots in the ground.
• Ferns: Adapted to living in the shade. No flowers to save energy, large green leaves to trap as much light as possible.
• Roots: The part of a plant that absorbs water and minerals from the soil.
• Buttress roots: A root that grows upwards from the ground to support the weight of the tree
• Drip tip: Leaves have thick waxy coats, sharp edges and a pointed tip to let the water drip off.
• Tropical desert: an area with an annual average precipitation of less than 250mm.
• Hot desert climate:

  • Less than 100mm rainfall a year.
  • Deserts are a long way from oceans so winds will be dry by the time they reach the area.
  • Not close to sea/large lake.
  • Trade winds like Harmatton from high altitudes are very dry so low rainfall in Sahara.
  • Blow over large areas of land hence no source of moisture.
  • High pressure means low rainfall.
• Camel adaptation:

  • Tough tongue and teeth.
  • Hump - store fats.
  • Sandy colour - camouflage
  • Long legs with leathery knees.
• CS: Desert areas threatened by human activities - Arabian Desert/Dhahban Desert:

  • Large herds of animals are grazed in the area which destroys pastures.
  • Resources/oil is mined in the area such as the Rub Al Khali in KSA. Large parts of the desert have been mined and wildlife is killed as habitat is destroyed. Aramco have build runways for its employees and some industry has been built which spoils the natural environment.
• CS: Desert areas threatened by human activities - Arabian Desert/Dhahban Desert:

  • Deeratna - Quad bikes/4x4 duning/trampling on the dunes wears them away. E.g. the deserts in Saudi (45 mins from Jeddah and Makkah) are big for desert safaris, quad biking etc. Tents are put up which damage the local environment.
  • BBQ are often left behind to burn away.
  • Music/belly dancing takes place which is often loud and creates noise pollution.