Topic 3 - Hot Deserts Flashcards
Geography Paper 1: Section B - The Living World: Topic 3 - Hot Deserts
How can we tackle desertification by using appropriate technology?
Appropriate technology reduces the need for removing trees for firewood.
People deforest the trees for firewood as a cooking fuel - seen as one of most damaging human activities in desert fringe areas.
Deforestation means there are no roots of trees to bind the soil together anymore so is baked by the sun + easily blown away by the wind, prohibiting any future regrowth.
Unsustainable but rural locals don’t have access to gas/electricity infrastructure.
“Efficient stoves” are an alternate way of cooking made locally using available materials like clay, and less wood and charcoal.
Some stove designs incorporate a thermocouple which generates sufficient electricity from heat to charge a mobile, which growing numbers of Sahel farmers own.
Mobile phone access is helping farmers to gain acces to weather forecasts, which helps them to prepare for drought/rain.
How can we tackle desertification by using magic stones?
Low stone walls are known as bunds/magic stones were introduced in the Sahel countries of Mali and Burkina Faso.
The stones are planted in lines parallel to the slope during heavy rain, forcing the water to spread over the soil so that it can be absorbed + slow the flow of rainwater over the baked ground (low permeability) so less is lost through run off.
Between 0.5 and 1.5m high + built by local people using basic tools and trucks to transport the stones - example of appropriate technology.
Increased yields by 50% in Burkina Faso + enhanced yields in comparison to other farmers in the country who did not apply magic stones on their land.
Argued by farmers to be more climate resistant - able to harvest all year round, others can only harvest in rainy seasons/years.
Increased revenue because of magic stones allows them to provide more for their families.
How has the Great Green Wall reduced challenges in the Sahel?
Before:
People were migrating away from the Sahel - scarce resources, inefficient
People living there were dependent on land for farming, agriculture and livelihood
Farmers + locals were in conflict over land - increasing hostility
Didn’t have garden
Africa’s Great Green Wall has:
allowed people to have a garden and sell produce in the shop they built
allowed land to become more efficient, grow more crops and increase food and security
reduced conflicts related to land depletion
can grow crops unable to before
How can we tackle desertification by planting trees?
Afforestation - Africa’s Great Green Wall 2007
An African-led movement with an ambition to grow a vegetated 8000km long and 30km thick natural wonder of the world across the entire width of Africa - Sahel.
It can’t be straight because of the changing landscape, mountainous - expensive and slower + will need different trees in diff countries due to diff climates
It runs through 11 countries, from Ethiopia to Senegal
Borders the desert - the Sahara, and the savannah
Ethiopia has the most trees (total restored area of around 2mill km)
Djibouti has the least trees (130 hectares of restored area)
Restored more than 18 mill hectares of land since its launch
Created more than 335000 jobs - funded by larger groups like the UN
Cost >$90mill across the 11 countries
What is appropriate technology? What are some of the challenges in the Sahel region?
Appropriate technology - using cheap, sustainable and available materials that local people can use. It is equipment and technology that is appropriate to the people using it.
Challenges in the Sahel:
majority of 50 million people - Sahel runs through 11 countries - live in poverty - economic
Niger is losing 250K hectares of farmland every year through desertification, millet crops have failed - economic
women in some villages walk up to 25km daily to fetch water - social/economic
What are causes of desertification in the Sahel?
Human causes:
pop growth - 1950, 30 mil ppl lived in Sahel, now as high as 1/2bil - caused by ppl having more children, life expectancy increasing + migration as mils of people forced into desert fringe areas by armed conflicts
as the pop rises, demand for resources increases -> overgrazing - livestock/goats feed for too long on vegetation
farmers also farm land more intensively, taking nutrients + removing natural vegetation - compress soil + reduce ability to hold water, allow soil to be blown away by wind - soil erosion
people collect more firewood - when trees are cleared, roots of trees no longer hold soil together so more likely to be blown away by wind
Physical causes:
climate change - hotter temps + less reliable rainfall reduce natural vegetation
no plants/leaves to absorb rainwater + soil left exposed to hot sun - bakes soil + cracks
when rains, runs over soil surface - soil can often be washed away
soil is degraded; losing fertility - vegetation cannot grow effectively
What is desertification? Where is impacted by desertification?
Desertification is the process by which fertile land becomes desert, typically because of drought, deforestation or inappropriate agriculture.
Has affected almost 36 million square km, including the Sahel region in the northern Africa - borders the Sahara desert and is the worst region impacted.
Smaller countries in Europe have very degraded soil
Niger, Chad, Sudan, Eritrea, Mauritania = at risk
South East Asia - at risk
Australasia = least degraded soil
Southern North America = at desertification
Peru, Chile, Bolivia = at risk
What are challenges experienced in the Thar Desert?
Lack of water - desert has low annual rainfall + high temps causing high rates of evaporation meaning water supplies have became a serious issue, especially as the population has grown and farming industries have developed, increasing demand. (Local risk of drought = global impact on trades, lack of efficiency - local social challenges like cholera/dysentery, health issues, famine, hygiene, desertification.)
Accessibility - many places are only accessible by camel, public transport often involves seriously overladen buses. (Can’t get to some places - can’t use resources in desert fully as can’t go to them/don’t have manpower to. Tarmac melts in temps over 50’C - unsafe as sticks to tyres.)
What are opportunities experienced in the Thar Desert?
Access to resources - the desert is rich in resources: kaolin - used to whiten paper, lignite coal, geothermal energy plant has been constructed there, phosphorite - used for making fertilisers. Improves global trade links + GDP, improves job opportunities + reduces reliance on farming.
Tourism - became popular tourist destination - 10,000s annual visitors. Locals benefit by proving food + accommodation + by acting as guides/rearing/looking after camels.
Farming - most locals involved in subsistence farming - surviving in hot + dry conditions by grazing animals on grassy areas.
Irrigation - main form = Indira Ghandi Canal - provide drinking water to many people in the desert - commercial farming has been made possible
Energy resources - sunny cloudless skies offer ideal conditions for solar power generations + home to India’s largest wind farm - The Jaisalmer Wind Park - reduces risk of energy shortages.
Where is the Thar Desert?
The Thar Desert is one of the major hot deserts of the world:
Found in between south east Pakistan and north west India, in the northern hemisphere.
Found just above the Tropic of Cancer - just above 30’ north of the equator.
Located near the Arabian Sea.
No rivers near the Thar Desert.
How do plants adapt to survive in the hot desert?
Prickly pear plant:
sharp spikes not leaves - reduce water loss + protection from predators
pads - store water during drought periods
open stomata at night - create CO2 - temps are less than 0’C, so doesn’t lose much water in the process - closed in day
waxy pads - reduce water loss as rainfall is low
Saguaro Cactus:
downward pointing spines - aim water at roots - temps can reach up to 50’C, so plants need a lot of water
spines - cool outer layer of plant
thick trunk - store up to 5 tonnes of water so plant can photosynthesise to make energy
more than 2000 seeds can lay dormant for years, but when it rains = easily pollinated
1 tap root = 3 feet long, short roots = closer to surface to suck up rainwater as rainfall as limited, helps plant to grow.
How do animals adapt to survive in the hot desert?
Scorpion:
can go for a year without eating food (not many insects to eat)
exoskeleton = hard outer shell, stops crushing
can burrow down in the sand to escape hot temps during the day
nocturnal - comes out in cooler temps
Camel:
stores FAT in humps = energy reserves in case of drought - not water
leathery knees to cope with heat + rugged ground
slit like nostrils = open + close to stop sand going in the nose, like in the case of sand storms (sand is very dry so wind blows it)
tough teeth + tongue - allows to eat desert plants - may be prickly/tough
2 toed feet = more surface area and stops from sinking into the sand
long eyelashes + bush brows - shade + reduce chance of sand blown in eyes
can drink salty water
colour = low albedo = highly reflective of sun/warmth = cool + camouflage
thick hair on back + neck (exposed in sleep) - reduce heat loss in night
less hair on body to lose heat during the day
concentrated urine + faeces to conserve water
What does a hot desert’s nutrient cycle look like?
Most nutrients are stored in the soil in a hot desert.
Climate influences biomass because plants optimally need a warm + moist climate to grow - meaning smaller in areas where not present. High rates of rainfall and temperatures = photosynthesis. Fast nutrient cycle = recycled quickly = more nutrient growth.
Transfers are slower in the hot desert as there is a lack of vegetation and rainfall.
Soils are infertile - surface run off - soil is compact in the hot desert so less water is absorbed.
Leaching + chemical weathering is minimal in the hot desert because there is minimal precipitation and moisture reducing them. Limited nutrients and rainfall in the hot desert.
What are soils like in a hot desert?
Some drought resistant cacti/flowering plants may grow there. Some organinc enrichment. Calcium nodules may be deposited. Rocky material deep down below the soil.
Little moisture reduce chemical weathering of rocks = thin + shallow soils which are sandy and grey in color.
The soil surfaces are impermeable due to beating rain on bare surfaces compacting them.
Due to the hot conditions, water evaporates off the surface of the soil, leaving salts behind. High salt levels in the soil prevent plants from absorbing water into the roots.
Organic matter is responsible for adding nutrients to the soil, so without the organic matter, the soils are mainly infertile.
Little amounts of organic content in the soil due to a low level of vegetation growing there.
The soil forming processes are limited by the shortage of water and vegetation - limiting water content - limited decomposition (hot and dry) as the soil needs to be moist for faster decomposition leading to limited plants and leaf litter.
What are characteristics of the hot desert?
The hot desert is a large-scale ecosystem, which are found along the tropics.
It has an annual average rainfall of less than 250mm.
It is cold at night time as there is a low cloud cover.
It has average annual temperatures of 27’C.
Hot and dry conditions.
Extreme diurnal temperature range - day vs night temp
Ground = cracked/baked dry - impermeable soil - so therefore when it eventually rains, the water will be unable to infiltrate into the soil = surface run off, like the tropical rainforest = both infertile soils.
Xerocles - animals adapted to hot desert
Xerophytes - plants adapted to hot desert
Case study = Thar Desert
Max temp - May = 34’C, Min - Jan = 16’C - range = 18’C
Long periods of little and unreliable rainfall
Min rainfall - Nov = 1mm, Max - July = 59mm - range = 58mm
Jul-Sep = 11x more rainfall than Jan-Apr
