The living world - Hot deserts Flashcards
Appropriate technology (or Intermediate technology)
Technology that is suited to the needs, skills, resources, knowledge and wealth of local people in the environment in which they live.
Biodiversity
The variety of life in the world or a particular habitat.
Desertification
The process by which land becomes drier and degraded, as a result of climate change or
human activities, or both.
Hot desert
An ecosystem that is characterised by high average temperatures and very low precipitation.
Mineral extraction
The removal of solid mineral resources from the earth. These resources include ores, which contain commercially valuable amounts of metals (e.g. iron and aluminium), precious stones
(e.g. diamonds), building stones (e.g. granite), and solid fuels (e.g. coal and oil shale).
Over-cultivation
Exhausting the soil by over-cropping the land.
Overgrazing
Grazing too many livestock for too long on the land, so vegetation cover is depleted and is
unable to recover.
Desert fringe areas
semi-deserts, semi-arid areas, drylands
borders of hot desert, they support greater biodiversity and larger plants
despite higher rainfall, still classified as fragile environment, at constant risk of desertification
Case study opportunities: The Western Desert, USA - mineral extraction
- rich reserves of copper, uranium and coal
- copper mining in Sonoran Desert –> open cast mining on a large scale since underground water found in ancient lava flow
Case study potential challenge of the opportunities: The Western Desert, USA - mineral extraction
- conflicts with other land uses i.e. tourism and farming
- contamination of water
Case study opportunities: The Western Desert, USA - tourism
- Grand Canyon and California’s Joshua Tree National Park, Colorado
- Museum in Parker, Arizona celebrates culture and heritage of Native Americans
- Las Vegas attracts 37 million visitors a year
- Lake Mead and Lake Powell attracts 2 million visitors a year for fishing and water sports
Case study potential challenge of the opportunities: The Western Desert, USA - tourism
- jobs encourage population increase in an already fragile environment
- tourists demand water –> showers, food requires huge amounts of water, swimming pools
Case study opportunities: The Western Desert, USA - farming
- Aquifer based farming in California’s Coachella valley produces lush crops of vegetables, lemons, peppers and grapes (–> wine)
- farmers allocated 80% of Colorado water despite it making up just 10% of the economy
Case study potential challenge of the opportunities: The Western Desert, USA - farming
- a lot of water is needed for irrigation of crops
Case study opportunities: The Western Desert, USA - farming. Why does it happen?
High temperatures and sunlight are favourable for agriculture
Case study opportunities: The Western Desert, USA - tourism. Why does it happen?
People have more money and leisure time
Chance to experience a wilderness area
Case study opportunities: The Western Desert, USA - mineral extraction. Why does it happen?
The area is rich in minerals - copper, uranium, lead, zinc, gold
Case study opportunities: The Western Desert, USA - energy
- Sonoran Solar Project (Arizona) energy for 100,000 homes and requires 360 workers to help build it
- Hoover Dam (Lake Mead) generates hydraulic power –> employed 5,000 people when in peak construction
- Navajo National oil and gas company for benefit of Navajo people –> 100 employees –> produce oil worth $50 million
Case study potential challenge of the opportunities: The Western Desert, USA - energy
- Hoover Dam increases evaporation
- contamination of water downstream
Case study opportunities: The Western Desert, USA - energy. Why does it happen?
Strong insolation, fantastic for solar power
HEP Hoover Dam
Fossil fuels (oil)
Carrying capacity
is the maximum number of people an area of land can support before environmental damage occurs
Case study: challenges of developing in a hot desert - extreme temperatures
- average temperature is 27 degrees C, summer temperatures can soar above 50 degree C
- work outside is very hard, especially for famers who have to work during the day
- leads to high rates of evaporation and water shortages
Case study: challenges of developing in a hot desert - water supply
- Colorado river has a very low flow between September and April
- silts and sands get trapped behind both dams –> river ecosystems change and many species are lost
- high temperatures cause evaporation
Case study: challenges of developing in a hot desert - inaccessibility
- low population density means that part of the Western Desert lacks surfaced roads
–> tourist and explorers must find their own way
–> extreme temperatures make this a dangerous place if your car breaks down - in 2015 elderly couple died of dehydration in the Los Coyotes Reservation near the edge of the Mojave desert
What are the causes of desertification?
- climate change
- population growth
- removal of fuel wood
- overgrazing
- over-cultivation
- soil erosion
Causes of desertification - climate change
- since 1970s the Sahel region of West Africa has experienced significant reductions in annual rainfall
- scientists believe climate change is disrupting the normal patterns of rainfall and causing more droughts
Causes of desertification - population growth
- in the Sahel region, population has increased from 30 million people in 1950 to almost 500 million
–> this is expected to double by 2050 - demand for food increases –> puts land under large amounts of pressure –> leads to vegetation destruction, soil erosion and ultimately desertification
- made worse by people migrating away from drought stricken regions or areas affected by war or natural disaster
Causes of desertification -removal of fuelwood
- millions of people living in semi-arid regions depend upon wood as their primary source of fuel
- when land is stripped of its trees, it is vulnerable to erosion by wind and rain –> can quickly become degraded and turn into a desert
Causes of desertification - overgrazing
- overgrazing by animals such as goats, sheep, cattle results in vegetation being stripped from an area and soil being left bare –> vulnerable to erosion
- happens because the available pasture land is reduced by natural causes (such as droughts) or human factors (such as political conflicts)
- population pressure can also lead to overgrazing
Causes of desertification - over-cultivation
- similar to overgrazing but takes place when land is over-cultivated for growing crops –> exhausting the soil of its nutrients
- soils in semi-desert regions are not very fertile and contain little organic matter
- when soils are over-cultivated - often in response to population pressure or restrictions in available land - the soil becomes dry, dusty and infertile –> then prone to soil erosion
Causes of desertification - soil erosion
- when vegetation is stripped or killed, the soil is left bare –> to be baked hard by the Sun
- when rainfall occurs, it washed over the hard surface, eroding rills and gullies and washing away the top soil
- this leaves behind very infertile sub-soil that cannot be used for anything
- soil can take thousands of years to form but can be eroded away in just a matter of hours
What are the causes of population pressure in fringe desert regions?
- natural increase
- migration
- armed conflict
What are the strategies that can be used to reduce the risk of desertification?
water and soil management –> addresses rainfall washing away loose soil and causing soil erosion –> often involves water storage and attempts to control the surface flow of water
tree planting –> protect soil –> roots bind soil together
use of appropriate technology –> low walls to manage water –> alternative cooking devices that uses efficient stoves
Definition of deserts
an area receiving less than 250mm of rainfall resulting in extreme aridity
Describe the location of Deserts
- found between 15 degrees and 35 degrees North and South of the equator –> where the air is sinking –> leads to areas of high pressure –> few/no clouds –> temp high in the day, low in the night
- the Tropic of Cancer and Tropic and the Tropic of Capricorn pass through most of the World’s Hot Desert regions
- there are no deserts located in Europe
diurnal temperature range
the difference between the maximum and minimum temperatures withing 1 day
Desert soils
- sandy, rocky soils
- typically about 1m deep
- often little organic material due to lack of vegetation
- may have white powder on the surface because salts are drawn to the surface by evaporation
irrigated
artificial process of applying controlled amounts of water to land
How are soil and vegetation interdependent?
- the canopy of leaves intercepts rainfall –> falls gently to the ground by dripping from leaf tips –> without this interception, raindrops would strike the soil, eroding the small soil particles
- the leaves provide shade –> can reduce air temperatures by up to 20 degrees C than in the open –> so soil stays cooler
- plants prevent the surface soil being baked in the heat –> without vegetation cover more moisture in the soil is drawn upwards from the surface
- roots of plants help to bind the soil together and prevent gulley erosion
State some primary consumers found in hot desert
insects, lizards, rodents, kangaroo rats
How do humans positively impact interdependence in hot deserts?
- sustainable land management practices
- wilding
- afforestation
- using underground or surface water at a sustainable rate
How do humans negatively impact interdependence in hot deserts?
- urbanisation putting pressure on scarce resources
- deforestation/removal of vegetation
- footpath erosion in busy places like the Grand Canyon, making soil vulnerable to blowing away
Challenges related to biodiversity
dry conditions
high temperature
short periods of rainfall
Plant adaptions - leaves
small, linear leaves or needles in order to reduce loss of water through evapotranspiration
leaves often also have a waxy resin, again to reduce evaporation
Plant adaptions - roots
adapted roots to make the most of sudden rainfall
some species have shallow roots that spread over a large areas
others have tap roots which run deep in search of water (up to 25m)
xerophyte
a plant that is adapted to living in an environment with little water
Examples of 4 animals that live in the desert
fennec fox
peringuey adder
kangaroo rat
camel
How are kangaroo rats adapted to hot deserts?
don’t sweat/have oily skin to reduce water loss
produce little urine
live in burrows during the day
don’t need to drink - get water from food
How are peringuey adders adapted to hot deserts?
move sideways - means less than 50% of body in contact with hot sand
How are fennec foxes adapted to hot deserts?
large ears help dissipate excess body heat
kidneys are adapted to restrict water loss
their extensive burrowing may cause the formation of dew, which can be consumed
they will receive moisture from their food
thick fur helps insulate them from the cold desert nights
sandy fur helps to reflect heat and provides camouflage
thick fur on the soles of their feet, which insulate against against the hot sand of the desert –> also provides excellent traction in the loose sand
How are camels adapted to hot deserts?
can go a week or more without drinking water and they can last several months without food
they can drink up to 32 gallons (46 litres) of water at one drinking session
store fat in the hump –> can be metabolised for energy
healthy body temperature is from 34-41.7 degree C –> allows camel to conserve water by not sweating as the environmental temperature rises
feet are wide so they can walk on sand more easily –> without sinking
thick lips so they can eat the prickly desert plants without feeling pain
ears covered with hair –> keeps out sand or dust that might blow into the camel’s ears
