deserts Flashcards
where are deserts found
subtropical areas 20 -30 degrees north and south of equator
what is the climate like
hot dry arid less than 250mm rain/year very cold nights due to lack of cloud
name the largest desert
sahara
what is sehel
long strip of semi arid dry land that borders south of the Sahara
what are desert fringes or drylands
border hot deserts
are deserts fertile
some are because of the nutrents needed for plant growh are present, once irrigated land can be productive
why do sand dunes form
in hot climates soil formination is limited by shortage of water and vegetaion. Weathering creates deep deposits of sand and loose material in some places wind build up tall sand dunes
what are the challenges to biodiversity in hot dessets
biodiversity is limited because of
dry conditions
high temperatures
short periods of rainfall
what are plants called
xerophytes they have thick waxy cuticle and shed leaves to minimise water loss by transpirtation
how are plants adapted for desert(4)
1 have the bulk of their biomass below ground where it is cool
2 cactus thick waxy cuticle has rolled leaves to reduce transpiration and water loss
3 trees have long roots to go deep into soil, short 4 fat trunks to store water and are fire resistent
4 flowering plants have seeds that only germinate after heavy rain and can lie dormant for years and 5 complete lifecycle quickly
6 lichens do not need soils to grow they get nutrients by using chemicals to break down rocks
can water be found in the desert
yes from aquifers or rivers eg nile
how have animals adapted to desert kangaroo rats (4)
1 kangaroo rats do not need to drink water they get it from food,
2 live in burrows during the day to avoid heat and do 3 not sweat,
4 they have kidneys which produce small amounts of urine
how has desert fox adapted to the desert (2)
1have thick fur on feet to protect from hot ground,
2 light coloured fur on bosy reflects sunlight and keeps them cool
what are abiotic components of the desert
soil rocks water
what interdependence exists in hot desets
links between parts of food web -
1 animals eating plants that gained nutrients from water and soil
2 vegetation roots stabalise the soil and plants stop soil from being blown away
What makes up USA’s western desert
3 hot deserts Mojave Desert Sonoran Desert and
Chihuahuan Desrt
what are the Western Deserts developmental opportunities
1urban residents can find work in retailing and service industries . In less populated areas farming, mineral extraction and tourism
what are aquifers
stores of water below desert brought to the surface from wells
can western deserts be farmed
yes high temperatures and sunlight are good if water can be fond
name 2 important sources of irrigation in western deserts
aquifers and canals
which minerals are western deserts rich in (5)
copper uranium lead zinc coal
why is it not all the minerals are extracted
there are possible conflicts with land use eg tourism and farming
which type of power are western deserts ideal for
solar power, there are also oil sources
which is the western deserts most become western desserts most important for of income
tourism
national parks heritage museums, las vegas entertainment water sports
why is there uneven development of western deserts (3)
1some of the environments are more challenging - to hot so no population
2 indigenous farm near water sources
3 accessibility can be challenging - lack of roads or it is dangerous if you break down in extreme temperatures train stations built near water sources
how have people adapted to the climate
1 traditional native homes were adapted to the climate earth houses made with wooden frames packed with clay and thatched with grass kept homes cool in day warm at night
before air conditioning flat roofs collected water
homes small to reduce sunlight getting in
whitewashed to reflect the sun
outdoors they wear wide brimmed hats to prevent sunburn
why was the hoover dam built
to supply water to the western desert during the summer when the colorado had low flow
what were the benefits of the hoover dam (2)
water brought to the cities throughout the western desert
colorado aquaducts bring water to farms and irrigate land agricultural benefits =41.5 billion per year
what are the disadvantages of the dam (3)
1 silt gets trapped behind the dam
2 and the water is colder changing the eccosystem and losing some species
3 sandbanks at the side of the river have been starved of sediment and this has caused some species to have decline.
4 the banks can no longer be used for fishing and rafting
what problems will the western desert face in the future
1 as the population grows there is a limit to the amount of water that can be taken from the colorado
climate change will effect the rainfall in an already scarce in water
what are the characteristics of desert fringe areas (3)
rainfall patterns are predictable
they support greater biodiversity and larger plants
more
drought resistent trees grow
why are desert fringes classed as fragile environment
climate change and poor land management can have huge impact so they are at constant risk of desertification
what is desertification
when habitable desert fringe areas are turning into hot desert areas
what is main cause of dersertification
change in natural rainfall cycle declining rainfall
will climate change result in less rain in deserts - why
we do not know if global temperatures rise there is a possibility of more rain in these areas due to the heating of the oceans and thus more water vapour in the atmosphere = more rain
but ckimate could become drier
what role does population growth and human factors have on desertification
1 population growth is linked with poverty and lack of education, growth caused by increase in children and people living longer
2 migration is another factor - drought and desertification in one region displaces people to another fragile area. As desertification happens there the number of people increase and the problem spreads
3 other people have been forced to move into desert fringe areas because of armed conflict
why has desertification become a problem in Darfur
1 one year in five brings drought - crops fail and cattle die
2 the ability to produce food has not kept up with growing population
3 conflict between nomadic farmers and settled farmers who fight over water supplies and land- it has led to overgrazing
4 some fled to refugee camps but this to has put stress on the land causing desertification
3 human causes of desertification in populated areas
1 overcultivation - overcroppng land exhausts soils fertility. more crops planted to cope with growing population
2 overgrazing - to many cattle grazing for to long eating all the vegetation means it may not be able to regrow because of new political reasons nomadic tribes can no longer leave land to let it recover
3 soil erosion - over cultivation and over grazing result in soil erosion. if vegetaion is eaten by cattle of destroyed by drought the exposed topsoil is baked hard in the sun. When rain eventually comes it washes over the soil rather than soaking into the ground as it flows it carries the topsoil away . making it impossible for vegetation to grow back.
what land management measures can help preserve soli quality and water (6)
1 tree planting schemes to bind and protect soil
2 planting grass on slopes to help stablise topsoil
3 collect rainwater on roofs
4 build small rock dams to trap water
5 build terraces on farmed slopes
6 construct low stone walls - bunds tjey help prevent flow over rainwater off baked ground and allows it to soak in
how does planting trees help with desertification
roots help to stabalise soil
decomposing leaf litter add nutrients
what is the green wall project
the plan to plant a wall of trees across the Sahel
it will secure physical environment and generate work and will help bring about political cooperation which might reduce conflict and number of refugee camps
what threatens the green wall project
climate change may prevent the survial of the trees
how can changing cooking methods help against desertification
removing trees for firewood for cooking and heating is most damaging human activity
it has increased with population growth
when trees are cut down soil errosion stops future regrowth
what is an alternative way of cooking (2)
using efficient stoves which are made locally using more available materials eg clay and use smaller amounts of wood or charcoal. Some can generate electricity to power a mobile phone which allows farmers access to weather forcasts and so can prepare for drought
move to solar power as well as energy for cooking earning can be used to tackle desertification
