Deserts Flashcards
characteristics of a hot desert
hot and dry
low biodiversity
little rainfall
define desert
an area receiving less than 250mm of precipitation a year
describe the distribution of deserts
along the tropics of cancer and capricorn
between 15 and 35 degrees north/ south of the equator
give 3 examples of deserts
sahara, arabian, sonoran
define diurnal
24 hour period
explain the location of deserts
at the tropics, air is sinking- this creates areas of high pressure so there is less clouds and rainfall
lack of cloud cover means hot days and cold nights
describe the characteristics of desert soils
sandy, infertile, rocky soils
1m deep
little organic matter due to little vegetation
white powder on the surface (salts drawn to the surface by evaporation)
interdependence between soil and plants
-roots of plants hold the soil in place and stop it from blowing away
-when the plant dies, decomposers break it down and return nutrients to the soil
-plants provide shade and stop the soil from drying out
-soil provides the plant with nutrients
positive human impacts on interdependence
afforestation
wilding
moving animals from area to area to allow land to regenerate
negative human impacts on interdependence
urbanisation- building cities
footpath erosion (E.g grand canyon) makes soil vulnerable to blowing away
overgrazing
reasons for low biodiversity
dry conditions- not ideal for plants growth
high temperatures
short periods of rainfall- plants grow quickly to make use of the rain, complete their life cycle quickly
define xerophytes
-plants that can survive in dry conditions
-some have waxy cuticles which reduces transpiration and minimises water loss
adaptions of the desert yellow daisy
waxy cuticles and small leaves reduces transpiration- minimises water loss
needles- protects against predators
adaptions of the prickly pear cactus
shallow roots which spread over a large area- absorbs as much rainfall as possible
adaptions of the saguaro cactus
grows slowly to conserve energy
stores it’s own water
adaptions of the fennec fox
large ears- rids of excess body heat
thick fur- insulation for cold nights
sandy fur- reflects heat, camouflage
hunts at night instead of day
adaptions of the kangaroo rat
dont sweat
produce little urine- conserves water
lives in burrows during the day
adaptions of the desert camel
store fat in their hump- used for energy
wide feet- walk on sand easily
thick lips- can eat prickly plants
case study desert
the western desert, USA
the western desert is made up of 3 smaller deserts- what are they
mojave, sonoran, chihauhau
what 3 states does the western desert cover
arizona, nevada, new mexico
tourism in western desert and challenges
lake mead- boating, sailing
need more water for hotels and tourists->lack of water for locals
farming in western desert and challenges
coachella valley- grow vegetables
only possible with irrigation->less water for locals
energy generation in western desert and challenges
sonoran solar farm- powers 100,000 homes
oil undergound- still dependant on fossil fuels
mineral extraction in western desert and challenges
earth is rich in minerals, E.g copper
uranium mining in grand canyon was halted due to conflicts between tourists and farmers
risk to wildlife species- habitat destruction
contamination of groundwater
define carrying capacity
the maximum number of people an area can support before environmental damage occurs
challenges in desert areas
inaccessability- lack of surfaced roads
water shortages- little rainfall
extreme temperatures- no cloud cover
management of water shortages
xeriscaping- changing the landcape, E.g instead of grass, have a rock garden
management of inaccessibility
highways- connect cities and deserts
E.g route 70 through Utah
travel by air
why are deserts inaccessible
low population density so a lack of surfaced roads
management of extreme temperatures
whitewashed walls- reflect heat
thick earth walls- keep homes cool
how many visitors a year to Las Vegas
37 million
define desertification
land becoming desert as the soil quality degrades over time.
explain over grazing as a cause of desertification
as the population increases, animals are grazed at a higher stock to feed more people. the animals eat the vegetation so amount of vegetation decreases.
soil is exposed to erosion and leaching
this makes soil infertile and dry
explain the cycle of desertification
amount of vegetation decreases
no plants to shade soil or intercept rainfall
soil is exposed to sun so it cracks
when it rains, water runs on the surface
nutrients are leached
soil becomes degraded and infertile
hard to grow crops
3 ways increasing population leads to the desertification cycle
- overgrazing animals to get more food for more people, animals eat vegetation -> lack of vegetation
- more people require more firewood for cooking, cut down trees -> lack of vegetation
- land is farmed more intensively to get more food for more people, takes nutrients from soil -> vegetation decreases
describe location of the Sahel region
sahel is a desert fringe area
stretches along central Africa
south of sahara desert
across countries like sudan, niger, chad
what is the sahel like
very low income
low life expectancy
population is 50 million
causes of population pressure in fringe desert regions
- conflict- refugees migrate to neighbouring countries. E.g civil war in south sudan.
- natural increase/ high birth rates- lack of family planning and contraception leads to high birth rates
causes of desertification
climate change- decrease in rainfall, vegetation decreases (less water for photosynthesis= less growth)
overgrazing- animals eat vegetation, soil becomes exposed to heavy rainfall, causes leaching and soil erosion
migration and refugees- leads to population increase, leads to overgrazing
management strategies to reduce desertification
encourage contraception- reduces overpopulation- reduces overgrazing
grow drought-resistant crops such as maize
rotate crops
management (water and soil) bunds
bunds are circles of stones placed on the ground
they hold water on the soil rather than letting it run quickly over the surface.
retains soil moisture for longer
not effective on uneven land
E.g Burkina Faso
management (tree planting)
tree roots bind soil together, prevents soil from blowing away
trees intercept rainfall, prevents leaching
E.g great green wall project 2007
-trees planted across the sahel
-brought 350,000 jobs
management (appropriate technology)
efficient stoves that burn small amounts of firewood- less trees cut down so there’s more vegetation
great green wall project 2007
line of trees across the sahel
less successful in chad and south sudan as they are dealing with conflict
brought 350,000 jobs
