The Living World - Hot Deserts Flashcards
Define a Desert
An area recieving less than 250mm of rainfall resulting in extreme arridity
Location of Hot deserts
15-30 North and south of the equator
Tropic of cancer and Tropic of capricon
along lines of Longtitude
Explain the location of the worlds deserts
Air is sinking near the tropics
Leading to areas of high pressure
This results in no clouds
Temperatures are therefore hot during the day and cold during the night
Diurnal temperature range
The difference between the maximum and minumum temperatures within 1 day
Characteristics of soil in deserts
Sandy, rocky soils
Typically about 1m deep
Often have little organic matter due to lack of vegetation
May have white powder on surface - salts drawn to the surface by evaporation
why is desert soil dry and not very fertile
lack of rainfall and sparse vegetation (little decomposing matter to enrich the soil)
how do plants affect soil and soil affect plants
Plants intercept rainfall to prevent soil erosion and excessive leaching
Plants provide shade to keep the soil cool - retain more water
Soils rely on plants to provide extra nutrients through dead vegetation and fixing chemicals
Soil provides the structure for roots to hold and grow
Plants rely on soils for nutrients
How can humans positively impact the interdependence of soils/water/plants/animals in hot deserts
sustainable land management practices
Aforestation
Using underground or surface water at a sustainable rate
How can humans negatively impact the interdependence of soils/water/plants/animals in hot deserts
Footpath erosion - soil is vulnerable to blowing away
Removal of vegetation
Agriculture - minerals from soil
Mining and mineral extraction businesses
xerophytes
plants that can survive in very dry conditions
how do plants adapt to the physical conditions
thick waxy cuticles and shedding of leaves to reduce transpiration
roots - shallow and spread over large area or roots than run deep in search of water
Example - Saguaro Cactus
Grows very slowly in order to conserve energy
Can store up to 9 tonnes of water
Verticla pleats that expand to allow greated water storage
Can lose 82% of its water before dying of dehydration
Example: Fennex Fox
Lives in the Sahara Desert
Adapted to cold nights
THick thur for insulation
Example: Camel
Lives in Sahara and other deserts
Adapted to not a lot of sources for energy
Fat is stored in the hump - it can bemetabolised for energy
Case study
Western Desert, USA
What states does the western desert cover
Arizona
New Mexico
California
Tourism in the western desert
+ Most important source of income
- stess on infasturcture
- Accessibility is difficult
why are tourists attracted
Wilderness areas - The Grand Canyon
Entertainment - economy of Las Vegas
Water sports - Lake Mead and Lake Powell
Mineral Extraction in the Western Desert
+ Source of income
- possible conflicts with land use
- enviromental concerns - risk to wildlife and endagered species, contamination of water supplies
Why does mineral extraction occur
Rich reserves of copper, uranium and coal
Energy in the Western Desert - The Sonoran Solar Project
+ provides employment
+ Provides energy for 10,000 homes
- Expensive
Why is the sonoran solar project happening
Strong insolation
Solar power can generate electricity
Farming in the western desert
+ economic oppurtunities
+ makes use of land
- Cost of irrigation
Why does farming happen
Desert conditions are generally favourable for agriculture
Low population density
WHta are the four main challanges od developing a hot desert
Water supply
Climate change
Transport + accessibilty
Climate
Challenges of water supply in a desert area
As temperature increases, Demand increases = not enough supply
Colorado river has sotred drinking water and irrigation since 1935
Low rainfall and high evaporation - secure water supply is essential for economic development
Challenges of climate change in a desert area
Semi arrid areas are one of the most fragile ecosystems
Climate change is disrupting rainfall patterns causing drought
Challanges of transport and accessibilty in desert areas
low population density = lack of surfaced roads
Access is limited from main cities
Limited road network - vast distances and high maintenance costs
Sand can blow over roads = tarmac melts
Chicago is connected to california through the western desert
Challanges of climate in a desert area
High temp = high rates of evaporation = water shortages
Working becomes hard for farmer
houses have thick walls to stay warm at night, white washed walls to reflect sun during the day
Extreme temperatures - hot and no rain
Desertification
The prcess of land becoming drier and degrading in quality due to both human activities and natural processes
Dessert fringe areas
Semi deserts, semi-arrid areas, dry lands
Borders of hot deserts, support greater biodiversity and larger plants despite higher rainfall
What are the six causes of deseritfication
Climate change
Population growth
Removal of fuel wood
Overtgrazing
Over cultivation
Soil erosion
how does increasaing population cause desertification
Animals are grazed at higher stock numbers to feed - animals eat more vegetation in the area
Land is farmed more intensevly - this farming takes nutrients out of soil and removes the natural vegetation
People collect more fire wood to keep warm at night or for cooking - deforestation
How does decreaseing vegetation contribute to the ‘cycle of desertification’
There are no plants or leaves to intercept rain so soil is left exposed to sun
The sun bakes the soil and it cracks
When it rains the rainwater runs over the surface of the soil rather than soaking in
This means that soil can be washed away
The soil is degraded losing fertility and structure
Soil is worn out/poor quality and it is harder to grow crops/vegetation
Example of a Fringe desert Area
The Sahel
Describe the location of The Sahel
5km long
Runs from west to East through the North of Africa
Runs alongside the great green wall
South of the Sahara Desert
causes of desertification in the Sahel
Natural - rainfall has decreased
Human - Population growth, overgraxing, greater demand for wood
What are the causes of population pressure in fringe desert regions
Natural increase - LICs = poor education on contraception
Migration to fringe areas - drought, poverty, civil war
If desertification occurs people move to fringe deserts
Significant factors causing desertification
Climate change - Global warming and rising temperature, changes in rainfall patterns
Population factors - High fertility among people, migration, poverty
Pressure on resources - Overgrazing, More wood, soil erosion
Facts about the Sahel
One of the poorest regions
Low preciptation - 100-300mm per year
Water scarcity = low crop production
3 Strategies to reduce the risk of desertification
Water and Soil management
Tree planting
Use of appropriate technology
Concept of Water and soil management
Involves water storage and attempts to control the surface of water
water and soil management example
BUNDS
- Low rock walls that follow contour lines
- Slows flow of surface water
- Soil is deposited on other side - then cultivated
Planting trees concept
Protects soil from direct impact of rain
Provides shade for vegetation
Roads bind to soil to prevent it being blown away
Example of Planting trees
The great green wall
- Plant trees across the edge of Sahara desert
- Tree roots bind to soil preventing it from blowing or eroding
- Leaf litter for nutrient cycling protects soil from rainwater
- Provide shade to stop ground drying up
Use of appropriate technology concept
Using cheap and easy technology
Accessible
Example of appropriate technology
Alternative cooking devices
- efficient stoves
- burns small amounts of wood
4 factors to think about when discussing appropriate technology
people
affordability
place
sustainable
