CIE IGCSE Geography
Revision Notes
IGCSEGeographyCIERevision Notes2. The Natural Environment2.5 Climate &
Natural Vegetation2.5.1 Climate Characteristics
2.5.1 Climate Characteristics
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Equatorial Climate Characteristics
World climate distribution
•
Climates vary across the world. The reasons for these climate types include:
o Latitude: with distance from the equator temperatures and sunshine
hours decrease as the solar radiation is more dispersed at the poles
and it has to pass through a greater amount of atmosphere
o Altitude: Increases in altitude lead to decreases in temperature
o Continentality: locations further inland heat up more quickly in the
summer and cool more quickly in the winter
o Ocean currents: warm and cold currents circulate in the oceans either
warming or cooling the adjacent land
o Aspect: in the northern hemisphere slopes facing south are warmer
o Prevailing winds: winds coming from warmer areas bring warmer air,
increasing temperatures
o Pressure systems: areas usually affected by low pressure such as the
equator have rising air, condensation and cloud formation leading to
more precipitation, whereas areas affected by high pressure have dry
conditions due to the sinking air
Equatorial climate distribution
Distribution of the Equatorial Climate
Equatorial climate characteristics
Characteristics
Location
Annual Precipitation
Temperature Range
Seasons
Humidity
Prevailing winds
Equatorial Climate
•
•
•
Low latitudes
Within the Tropics 23.5° north and south of the equator
Amazon in South America, New Guinea, South-east Asia,
Zaire Basin
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Over 2000mm
•
•
•
low range of mean monthly temperatures - 26-28°C
Constant high temperatures
Diurnal range is about 7oC
•
No seasons - hot and wet all year round
•
High, usually over 75-80%
•
Winds blow into the equatorial region from high pressure
areas to the north and south.
The winds from the north blow from the north-east and the
winds from the south blow from the south-east.
•
•
The winds are known as the trade winds
Climate graph for Iquitos, Peru
Factors influencing the equatorial climate
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There are a range of factors which influence the climate including:
o The midday sun is almost directly overhead all year meaning there is
maximum insolation
o Low pressure all year which leads to rising air, condensation, cloud
formation and high precipitation levels
o Dense vegetation cover leads to high levels of evaporation and
transpiration
o The warm air stores large amounts of water vapour until the
temperatures start to cool in late afternoon which then leads to heavy,
daily convectional rainfall
Hot Desert Climate Characteristics
Hot desert climate distribution
Distribution of the Hot Desert Climate
Hot desert climate characteristics
Characteristics
Hot Desert
•
Location
Annual Precipitation
Temperature Range
Seasons
Humidity
Prevailing Winds
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15° - 30° north and south of the equator (tropical and subtropical)
North Africa - Sahara, Southern Africa - Kalahari and
Namib, Australia. Middle East
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Below 250mm
•
•
•
•
Daytime temperatures can reach 50°C but average around
25°C
Night-time temperatures below 0°C
Diurnal range is large up to 45°C
Annual range is around 15°C
•
Summer and winter
•
Low often between 10-30%
•
The winds are offshore blowing from the east across the
land, so they do not collect any moisture
Climate Graph for Jeddah, Saudi Arabia
Factors influencing the hot desert climate
•
•
•
•
High pressure all year which means the air is descending and warming so
precipitation does not occur because the air is not rising
Prevailing winds are often from over land masses which means they contain
little moisture
Some deserts are in a rain shadow so there is little rainfall
Cold ocean currents on the west side of continents may reduce summer
temperatures due to the cooling effect of the ocean
Influence of pressure systems
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Hot deserts form between 15o- 30o north and south of the equator as a result
of the atmospheric pressure systems
o
o
o
o
Air rises at the equator and when it reaches the upper atmosphere it
moves north and south
The air cools and starts to sink
This creates a zone of high pressure at about 30o north and south of
the equator
Due to the sinking air, warm air cannot rise, condense and form clouds.
This results in high aridity
Atmospheric Pressure Systems
Worked example
Explain how high atmospheric pressure influences the climate of hot deserts.
[3]
•
Answer:
o Air is descending [1]
o
o
o
It heats up/does not cool [1]
Condensation does not occur/clouds do not form [1]
Precipitation is low/does not occur/drier/only has e.g. 250 mm per
annum etc [1]
CIE IGCSE Geography
Revision Notes
IGCSEGeographyCIERevision Notes2. The Natural Environment2.5 Climate &
Natural Vegetation2.5.2 Ecosystem Characteristics
2.5.2 Ecosystem
Characteristics
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Tropical Rainforest Ecosystem Characteristics
•
•
The Tropical rainforest (TRF) biome is mainly found in a band between
15o north and 15o south of the equator within the equatorial climate zone
Covering only 6% of the Earth's surface the main areas of tropical rainforest
ecosystem are in the following countries;
o Amazon which is the largest remaining rainforest on Earth usually
associated with Brazil but covers parts of seven other countries
o Central America including parts of Belize, Costa Rica, El Salvador,
Guatemala, Honduras, Nicaragua, and Panama
o Central Africa including Cameroon, the Central African Republic, the
Republic of Congo, the Democratic Republic of Congo (DRC),
Equatorial Guinea and Gabon
o Indo-Malaysia, including Malaysia, Indonesia and a number of other
countries in South-East Asia
Biodiversity
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TRFs contain the highest biodiversity of plants and animals on Earth
o Estimates range from over 50% to 80% of the world's plant and animal
species
o One 10km2 area can contain up to 1,500 flowering plants, 750 species
of trees, 400 species of birds and 150 species of butterflies
Nutrient cycle
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The TRFs have a continual growing season with high rainfall and
temperatures all year round
The nutrient cycle is rapid
o
o
o
Trees and plants lose their leaves all year round
The high level of moisture and high temperatures leads to rapid
decomposition and recycling of nutrients
Plants grow quickly which leads to a rapid uptake of nutrients from the
soil
Tropical rainforest nutrient cycle
•
The result of this rapid nutrient cycle is that the soil in the TRF is not very
fertile
Structure of the tropical rainforest
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The TRF has five distinct layers
o Ground layer (0m)
o Shrub layer (3-4m)
o Under canopy (15m)
o Canopy (30m)
o Emergents (45-55m)
Tropical rainforest structure
Adaptations
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The plants and animals within the TRF are very well adapted to the climate
conditions
Plants
Animals
Waxy leaves with drip tips - these ensure that
rainwater runs off the leaf and does not remain
which would encourage mould growth or break
the leaf
Sloth - algae grow in the fur of the sloth helping
to camouflage it
Buttress roots - these large roots above the
ground which help to support the very tall trees
because the roots below the surface are shallow
Toucan - has a large bill to reach and cut fruit
from the branches of trees
Lianas - vines which use the tall trees as support Primates - have prehensile tails to help them
to reach the sunlight
climb trees
Epiphytes - these are plants which grow on
trunks and branches of trees getting nutrients
from air, rain or debris accumulating around the
plant
Geckos - have large, flattened toe pads with
sticky scales which allow them to grip the
smooth tree trunks
Straight, smooth trunks - to reduce the number Stick Insects - their stick and leave shapes help
of epiphytes using the tree
them to be camouflaged
Exam Tip
You may be asked to describe the rainforest vegetation characteristics. As well as
adaption features remember to include information about the different layers and
heights of each layer.
Food web
•
As in all ecosystems the TRF has a complex food web which includes
o Producers
o Primary consumers
o Secondary consumers
o Tertiary consumers
Tropical rainforest food web
Worked example
Study Fig 1, which is a diagram showing information about a tropical
rainforest ecosystem in an area of equatorial climate
Suggest reasons why some animals live in the canopy but others live in the
ground cover in a tropical rainforest.
[3]
•
•
You need to consider the adaptations and diets of the animals which may lead
them to live in a specific layer
Answer:
o Some are able to climb/fly whereas others are not [1]
o Some need shelter/protection [1]
o Food supplies available (in canopy/at ground level) [1]
o Different habitats/nesting areas etc [1]
Hot Desert Ecosystem Characteristics
•
•
Hot desert biomes are mostly found in a band around the Tropic of Cancer
and Tropic of Capricorn
Approximately 20% of the Earth's surface is covered by hot desert
ecosystems including in the following areas;
o North America - the Mojave and Sonoran Deserts of the USA and
Mexico
o South America - the Sechura Desert in Peru and the Atacama Desert
in Chile
o Africa - the Sahara, Kalahari, Namib and Somali Deserts
o Middle East - the Arabian Desert
o Asia - the Dasht-e Lut in Iran, the Gobi, Turkestan, Thar and
Taklamakan Deserts
o Oceania - the Australian Desert
Biodiversity
•
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Hot deserts have one of the lowest biodiversity of plants and animals on Earth
The hot desert biome supports approximately 5000-6000 plant species, many
invertebrates and up to 20 species of bird
Nutrient cycle
•
•
•
The growth of plants is limited due to the extremes of temperature and lack of
water
The nutrient cycle is very slow
Most nutrients are stored in the soil
Hot desert nutrient cycle
•
Due to a lack of organic matter the soils are coarse, sandy and low in
nutrients
Adaptations
•
To be able to survive the extreme temperatures and lack of rainfall the plants
and animals are extremely well adapted
Plants
Animals
Camels have a range of adaptations including
two sets of eyelashes and nostrils which close to
Low growing - this helps to avoid water loss due
keep sand out of their ears and noses. They also
to strong winds
store fat in their humps so they can survive for
long periods without food or water
Fennec Fox - have large ears which help them to
Thick stems - used to store water
lose heat
Shallow roots - these spread out near the surface Burrowing - many animals burrow to avoid the
to catch whatever rain falls
intense day time heat
Long roots - some plants have long tap roots
Insects and reptiles have waterproof skin to
instead of shallow roots to reach water deep
reduce water loss
underground
Small leaves or needles - the smaller surface
area reduces water loss
Nocturnal - some animals hunt at night to avoid
the daytime heat
Food web
•
As in all ecosystems hot deserts have a complex food web which includes
o Producers
o Primary consumers
o Secondary consumers
o Tertiary consumers
Hot desert food web
CIE IGCSE Geography
Revision Notes
IGCSEGeographyCIERevision Notes2. The Natural Environment2.5 Climate &
Natural Vegetation2.5.3 Deforestation of Tropical Rainforest
2.5.3 Deforestation of Tropical
Rainforest
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Test Yourself
Deforestation of Tropical Rainforest in Malaysia
•
•
Deforestation is the felling and clearance of trees
Malaysia, Brazil, India and Indonesia are experiencing the highest levels of
deforestation in the world
o The Malayan government has in the past failed to provide the Food
and Agriculture Organisation (FAO) with figures for forest loss
World Deforestation 2015
•
•
There are six main human causes of deforestation
Wildfires are a natural cause of deforestation:
o The frequency and severity of wildfires have increased this is linked to
human induced climate change
Human Causes of Deforestation
Exam Tip
It is important to remember that deforestation is often the result of a combination of
factors which are linked together rather than any one cause. For example, the
growth of settlements also leads to more land being cleared for agriculture to support
the people in the settlements.
Environmental impacts of deforestation
•
Many of the impacts of deforestation are environmental including:
o Areas that have been deforested are planted with monoculture which
reduces biodiversity
o Interception and infiltration decrease which
reduces evapotranspiration and as a result precipitation decreases
o This also increases overland flow which leads to soil erosion
and sedimentation of the rivers
o Sediment builds up on riverbeds reducing their capacity and increasing
the flood risk
o Lack of interception increases the leaching of nutrients
o
Fewer trees increase the amount of CO2 in the atmosphere adding to
the enhanced greenhouse effect
Impact on the nutrient cycle
•
•
The majority of nutrients in the tropical rainforest are held in the biomass
When trees and vegetation are cleared by deforestation the main store of
nutrients is removed
IMAGE
Environmental Impacts of Deforestation
Social impacts of deforestation
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Indigenous communities have less land to sustain their traditional way of life
this means:
•
o
o
•
•
•
•
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Land does not get the opportunity to recover
Less food available
Improved quality of life for some people due to increased income and jobs
Indigenous communities may give up their way of life leading to a loss of
culture and traditions
Increased risk of landslides which can destroy homes and block roads
Loss of potential medicines
Increased risk of flooding settlements
Economic impacts of deforestation
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•
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More jobs available in mining, forestry, agriculture and HEP
Increased income for the country through the export of goods from the forest minerals, timber, crops
Almost a quarter of Brazil's GDP comes from activities in the deforested areas
of the Amazon
Worked example
Explain why large amounts of deforestation have occurred in tropical
rainforests.
[5]
•
•
•
In your answer you need to explain which means that you if you just state
road building for example you will not achieve the higher marks
You need to explain that road building happens to access remote areas of
forest and requires large areas of trees to be felled and removed
Answer:
o Economic development (for country)
o To earn money (individuals)/valuable wood
o Large area so difficult to monitor
o Corruption
o Logging/timber/furniture/paper
o Firewood/charcoal
o Cattle grazing/ranching/rearing livestock
o Cash crop farming/palm oil/plantations
o Settlement/urban growth/examples of buildings e.g. schools
o Road building/railways
o Mining/quarrying minerals or example e.g. gold
o HEP/dams etc.
Example Case Study: Malaysia
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Malaysia is located in Southeast Asia
Location of Malaysia
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Almost 70% of the land is covered by tropical rainforest
Climate
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The climate of Malaysia is typical of tropical rainforest climates with high
rainfall and high temperatures all year round
Climate Graph of Kuala Lumbar, Malaysia
•
The Malaysian rainforest has high biodiversity with over:
o 15,000 plant species, including 5,500 flowering plants and 2,600 tree
species
o 750 bird species
o 250 mammal species
o 350 reptile species
o 190 amphibian species
o 350 fish species
o 1000 butterfly species
Malaysian Rainforest Food Web
Adaptations
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There are many ways in which the animals and plants have adapted to the
rainforest climate including:
Plants
Animals
Pitcher plants - some of these
are epiphytes which grow on other structures Hornbill - the distinctive bill has multiple
like trees and get their nutrients from
uses. The bird uses it to help it climb trees,
capturing insects in a funnel which contains a like a trowel for digging
sticky acidic liquid which dissolves the insect
Orangutans - long and very strong arms
Orchids - these are epiphytes which grow on which enable them to move easily through the
other structures such as trees to reach the light trees. Fingers and toes are long used for
gripping tree branches
Malayan Tapir - their colour pattern helps to
Lianas - these are vines which attach
camouflage them, and they use their long nose
themselves or wrap themselves around trees to
to forage on the forest floor for leaves, fruit
reach the light
and nuts
Kapur tree - grows up to a height of 60m to
Mulu Flying Frog - can change colour to
reach the light. It has a straight branchless
camouflage it and it uses flaps of skin on its
trunk to deter epiphytes and lianas from
legs to glide from tree to tree
growing on it
Deforestation in Malaysia
•
•
It is estimated that Malaysia has the fastest rate of deforestation in the world
Since 2000 an average of over 140,000 hectares of forest has been felled and
cleared each year
Causes
•
•
•
•
Logging
o Malaysia is the largest exporter of tropical hardwoods
o Although Malaysia has environmental protection policies there is still
evidence of illegal logging in areas of Borneo
o Selective logging is the dominant type of logging but this requires road
construction and settlements which result in deforestation
Energy
o The construction of dams to provide Hydroelectric power result in
flooding of large areas of forest
o The Bakun Dam will result in 700km2 of land being underwater in
Sarawak, Malaysia
Mining
o Tin mines are widespread and require deforestation for the mine itself
but also for road construction
o An iron ore mine planned for the Som Forest Reserve will result in the
deforestation of over 60 hectares
o There is also drilling for oil and gas
Commercial plantations
o Malaysia exports over 30% of the world's palm oil and is the second
largest producer
Many palm oil processes now adopting a zero-deforestation policy so
that they do not buy palm oil from deforested areas. However, Clear
felling permits are sometimes used in Malaysia to clear land and then
sometime later another company will plant palm oil
Settlements
o Up to 1980 people were encouraged to move to rural areas from the
cities to try and reduce the pressure on urban areas
▪ This led to the deforestation of approximately 15,000 hectares of
rainforest
Subsistence farming
o This can sometimes involve slash and burn where areas are cleared
using fires - these can sometimes get out of control and destroy large
areas of rainforest
o
•
•
Effects of deforestation
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•
•
•
•
Soil erosion
o Without the tree roots to bind the soil, the soil is more easily eroded by
wind and rain
o Exposed soil is more vulnerable to leaching of nutrients and the soil
becomes less fertile
Loss of biodiversity
o Habitats are destroyed and the ecosystem affected by deforestation so
the variety of plants and animals decreases
o Oil Palm plantations lead to a 35% reduction in species
o Orangutans, pygmy elephants, Sumatran Rhino and Malayan
tigers are all endangered
Local climate change
o Reduced transpiration and evaporation leads to a decrease in
precipitation and an increase in temperatures
o Rainfall patterns become less reliable and more extreme
Global climate change
o Felling of the trees leads to a decrease in the absorption of carbon
dioxide
o Increases carbon dioxide concentrations in the atmosphere and as this
is a greenhouse gas this increases human induced climate change
o Use of fire for clearance also increases carbon dioxide emissions
Indigenous communities
o Indigenous communities such as the Orang Asli and Temiar have
been forced off land
o Pollination of fruits has reduced due to a decrease in pollinating insects
and animals such as bats
▪ This has reduced the available food sources
o In Kuala Koh village 2019 at least 15 indigenous Batek died after an
outbreak of disease possibly transmitted by loggers working near to the
village
Example Case Study: Hot Desert, Namib Desert
•
The Namib Desert is located mainly in Nambia on the west coast of Southern
Africa
Location of the Namib Desert
•
•
Stretching for over 2,000km from Angola in the north to South Africa to the
south
The desert is 160km wide
Climate
•
The highest day time temperatures can reach over 45oC
•
•
•
•
Night time temperatures can be as low as 0oC
The areas nearest to the coast are cooler due to the effect of a cold ocean
current - the Benguela current
The cooling effect of the ocean can also lead to the formation of fog which can
affect coastal areas more than half the year
Annual precipitation varies between 2-200mm a year
Climate Graph of Swakopmund
•
The Namib Desert has many species which are endemic and has higher
levels of biodiversity than other hot desert areas
o There are approximately 3,500 plant species over 50% of which are
endemic
o 200 mammal species
o 268 reptile species
o Over 6000 insect species
Adaptations
•
There are many ways in which plants and animals have adapted to the Namib
Desert's unique climate, including:
Plants
Animals
Welwitschia mirabilis - with just two leaves
this plant only grows when conditions are
Fog basking beetle - gathers water by standing
favourable. The long leaves wrap around the
on its head in a morning whilst the fog
bottom of the plant to give shade to the roots and
condensates on its back and trickles down to its
reduce water loss. The colour of the leaves
mouth
change turning red when it is very hot to protect
the plant from the sun
Nara plant - this plant has spikes instead of
Desert elephant - have smaller bodies, broader
leaves to reduce water loss and it absorbs the
feet and longer legs than other elephants. The
water droplets from fog through its stems. The
broader feet help to spread their weight on the
bottom of the plant dies off as it is covered with
sand and the smaller body.
sand, this provides nutrients for the new growth
Quiver Tree - these are succulents, they can
store water in their trunks and branches due to
the spongy fibre. Their leaves also store water Wheel spider - these are nocturnal and so hunt
and have a smooth waxy surface to reduce water at night when temperatures are cooler
loss. The yellowish bark helps to reflect the sun's
heat
Golden mole - with powerful digging claws,
Camel Thorn Tree - has a strong tap root which
dense fur which repels dirt so they can almost
can grow up to 60 meters allowing it to absorb
swim through the sand. With very efficient
water from deep underground
kidneys they do not need to drink much water all
Threats and impacts on the desert ecosystem
•
•
Tourism
o
Increasing tourism to the Namib desert has led to more activities such
as off-roading and sand boarding
o Estimates suggest that desert soil takes over 2000 years to recover
from being driven over
o Vehicles destroy the small, but essential lichens and plants which are
the foundation of the food web
Mining
o Mining for diamonds, uranium, copper and zinc all occur in the Namib
desert including the Rössing uranium mine near Swakopmund
o Involves the removal of large areas of sand which then destroys plant
and animal habitats
o Increased pressure on scarce water resources due to the amount of
water used in processing
o Increase in air, soil and water pollution
o Toxic waste may leach into the ground (leachate) which affects water
sources
•
•
Agriculture
o Irrigation increases salt levels in the soil and reduces the plant life
o Increases the pressure on scarce water resources
o Over-grazing in increasingly limited areas reduces the number of plant
species and has impacted on the Golden Mole population
o Farmers shoot and kill the desert lion as they view it as a threat to
their livestock. This lion is now on the vulnerable species list
Poaching
o Illegal poaching of animals such as the pangolin has impacted on the
food web
o Black rhino numbers have also decreased significantly as a result of
illegal poaching
Worked example
Study Fig 1, this shows a waste heap produced by the mining of copper ore.
Suggest how this may pose a threat to the natural environment
[3]
•
Answer:
o loss of vegetation [1]
o loss of animal habitats [1]
o covers a large area [1]
o waste could be toxic/toxic leachate [1] affecting rivers/groundwater
(dev.) [1]
o visual pollution [1]