Hot deserts 1 Flashcards
Characteristics, desertification, plant and animal adaptations
What are the conditions of a hot desert?
-Hot, dry ecosystems
-Harsh environments
-Extreme temps (huge diurnal range)
-Little rainfall
How much rainfall does a hot desert receive per year?
under 250mm
What is the diurnal range of hot deserts?
-Up to 45°C during the day
-Can drop below 0°C at night
The harsh environment means that…
…plants and animals have lots of adaptations to suit the difficult conditions.
What is interdependence?
How two or more species depend on each other.
Describe the interdependence of plants and animals in hot deserts.
-Plants take up nutrients from the soil and provide water and nutrients to the animals that eat them.
-In turn, animals spread seeds through their dung, helping plants to reproduce.
Describe the interdependence of climate and soils in hot deserts.
-The hot and dry climate affects soils
-High evaporation rates mean soils are salty
-Soils are relatively low in nutrients as there is little decomposition of dead material by fungi and bacteria
Describe the interdependence of soils and plants/animals/people in hot deserts.
-Little decomposition means infertile soils
-This means that plants struggle to grow
-Sparse vegetation limits the amount of food available
-Which means that deserts can only support low density populations of animals and people
Biodiversity
The variety of all the different species of organisms living in an ecosystem(plants + animals)
Why is biodiversity in hot deserts low?
-Little rainfall and extreme temps make it hard for plants and animals to survive
-Soils are infertile so nutrient cycling is very slow
How will climate change impact biodiversity in hot deserts?
It will lead to more extreme temperatures which make survival even harder. So, it will lower biodiversity.
Camel adaptations
-Thick insulating fur
-Hump (stored fat) that can be broken down for nutrients
-large, thick, wide feet preventing the camel sinking into the sand, or getting burnt by it
-2 sets of interlocking eyelashes (see in sandstorms)
How is thick insulating fur an advantage for animals in hot deserts?
-Protects them from the sun by day
-Keeps warmth in by night
-(so insulates both from cold and heat)
Fennec fox adaptations
-Thick insulating fur
-They live in underground burrows (where the heat is less extreme)
-Small to shed heat faster
-Large ears give them a large surface area to lose heat from
-Camouflage coat (protects from predators)
-Furry pads on feat (maximum traction across sand)
Hot Desert animals are adapted to…
…cope with the harsh (hot and dry) physical conditions.
Hot desert plants are adapted to…
…cope with the high temperatures and limited supply of water
Cacti adaptations
-Are succulents (store water in stems)
-Have thick, waxy skins (to hold water and reduce the rate of transpiration)
-Spines
How are spines on cacti an advantage?
-Having spines rather than leaves reduces the surface area through which water can be lost by evaporation
-They often contain toxins to protect from predators (such as Jackrabbits)
Mesquite tree adaptations
-Taproots which are long to reach deep water supplies (up to 50m underground)
-Fibrous roots
Fibrous roots
Laterally spreading roots widely dispersed around the tree, near the surface of the ground, to absorb as much water as possible when it rains.
Where is biodiversity the highest in hot deserts?
Around water sources, such as oasis.
Why is biodiversity in hot desert environments particularly vulnerable to human activity?
-Most animal and plant species live near water sources
-This is also where human populations are the highest
-Human activity in these areas is therefore likely to have a negative impact on biodiversity
-If water sources are used up (e.g. for irrigation) or contaminated (e.g. by livestock) there is no water available for animals and plants so they might die
-Also, human activities are thought to be contributing to climate change
-CC is likely to cause temperatures in hot deserts to become even more extreme (hotter during the day and colder at night)
-So species that are not adapted to these conditions may die out or have to migrate
What is desertification?
The process by which semi-arid land becomes desert.
How does population growth cause desertification?
-There is a clear link between migration and desertification
-More people in an area puts more pressure on the land by increasing the likelihood of overcultivation and animals overgrazing
How does climate change cause desertification? (rainfall)
-It will reduce rainfall in areas that are already dry
-This means less rainfall is available for plant growth, so more plants will die, which reduces biodiversity
How does climate change cause desertification? (temps)
-As global temperatures are increasing, more water will be evaporating from the land
-This makes the soil drier, so plants will struggle to grow, and soil erosion is more likely
How does desertification in one area lead to the risk desertification in another?
Desertification often causes people to migrate which puts pressure on the land they’ve moved to, increasing the risk of desertification there too.
How does overgrazing cause desertification?
-Allowing cattle to overgraze can lead to soil erosion as the vegetation is eaten away faster than it can regrow.
-Fewer plants stabilising the soil increases the risk of desertification in that area.
-The trampling of the soil by animals also erodes it.
How does over-cultivation cause desertification?
-Crops are grown to provide food or to sell as produce for profit
-Too many crops in an area can lead to soil degradation, whereby the soil loses its nutrients before it has time to replace and recharge them.
-This leads to desertification.
How does soil erosion cause desertification?
-Once the top-soil layer is removed from an area by either wind or water, this makes it harder for vegetation to grow.
Each time land is used for grazing or crops…
…the soil loses fertility.
How does the removal of fuel wood cause desertification?
-Indigenous people who live in the desert rely on wood for fuel to heat their homes and cook as these communities aren’t often developed.
-Cutting down the few trees there are in the desert leaves the soil exposed, and the area at risk of desertification.
Name the activities which can lead to desertification.
-Population growth
-Overgrazing
-Over-cultivation
-Soil erosion
-Climate change
-Removal of fuel wood
What is soil erosion?
The removal of top-soil (containing the most nutrients) from an area by either wind or water.
What strategies can be used to combat desertification?
-Water and soil management
-Tree planting
-The use of appropriate technology
Why it it the areas on the fringes of hot deserts that are at risk of desertification?
These areas are most vulnerable to human activity as most people who live in deserts live on the fringes (or around water sources).
Activities such as over-cultivation and allowing animals to overgraze can lead to an increased risk of desertification.
How does water management combat desertification?
-Growing crops that need little water reduces water use
-Techniques can be used to make sure that the little water available is being used efficiently
-For example, farmers could use drip irrigation techniques instead of surface irrigation to water crops, which ensures that the soil isn’t eroded by lots of water being added at once.
How does soil management combat desertification?
-Leaving areas of land to rest (fallow) between planting crops, or letting animals graze, lets the soil recover its nutrients
-Rotating crops that take different nutrients from the soil prevents the same nutrients being continually removed
-Compost can be used to add extra nutrients to the soil
How does tree planting combat desertification?
-Trees act as windbreaks, reducing soil erosion by wind.
-Trees can stabilise the sand, preventing the desert from encroaching on farmland (by increasing soil fertility and water retention).
-If grown in amongst crops, the trees provide shade which reduces temperatures and evaporation rates.
How does the use of appropriate technology combat desertification?
-Appropriate technology is technology suited to the needs, wealth, and knowledge of people who live in a local area
-This means that it is cheap and easily available to them.
-It often provides sustainable solutions that help to combat desertification
-For example, sand fences can be constructed to stabilise the soil, reducing erosion
-Solar cookers reduce the rate of deforestation as they use the sun’s energy to heat food.
Native
An animal/plant that lives in an area.
Indigenous
An animal/plant that has always lived in an area.
Endemic
An animal/plant that only lives in one area and cannot be found anywhere else.
What are temperature like in hot deserts? Why?
Extreme due to a lack of cloud cover. (temps can reach 45 degrees during the day and 0 degrees at night). We would call this an extreme diurnal range.
Pressure is …
…permanently high.
Describe the location of hot deserts.
Hot deserts are mainly found on or around the tropics of Cancer and Capricorn (30 degrees N and S of the equator).
They are found in every continent bar Antarctica.
The largest hot deserts are found in Africa and Australia, the largest in the world being the Sahara in Northern Africa.
For an area to classify as a desert, it needs…
…less than 250mm of rainfall per year.
Is soil fertile in hot deserts? Why?
No.
There are few plants and animals in hot deserts.
This means that very little decomposition occurs, which means that the soil cannot gain many nutrients from the dying plant and animal material.
Hence, it is infertile.
Semi- arid land
An area on the fringe of a desert with semi- fertile soil. These areas are vulnerable to soil erosion and desertification.
Overgrazing
Farmers have more livestock in an area than the environment can sustain. This can damage the whole ecosystem.
How many seasons do hot deserts have?
2 (The summer being the part of the year where it is significantly warmer).
(or the wet and dry season).
How many people live in hot deserts?
Over 1 billion.
Biodiversity in hot deserts.
Hot deserts have a relatively low biodiversity.
Small areas around ephemeral (temporary) ponds and rivers or along the desert margins have the highest levels of biodiversity, and contain a high proportion of species that are endemic (unique) to the desert.
Areas with water also have the highest density of human populations.
How can people threaten biodiversity in hot deserts?
People can threaten biodiversity by increasing desertification and by over contaminating water supplies.
Give an example of how changing one part of the ecosystem will have a knock on effect.
Allowing cattle to overgraze can cause soil erosion.
With fewer plants stabilising the soil, the wind can blow fine sand particles into the atmosphere, forming dust clouds.
This reduces rainfall, making deserts even drier.
Without rainfall, water supplies can dry up and people, plants, and livestock may die.
The nutrient cycle is …. than that of tropical rainforests, and involves …
much slower
fewer nutrients
Why are hot deserts sterile environments?
Bacteria cannot function without water/moisture.
What human factors might affect the nutrient cycle?
Overgrazing
Burning firewood
What physical factors may affect the nutrient cycle?
Dry climate
Low rainfall
Tree planting example
In the Sahara desert there is a project called the ‘Great green wall’ - a wall of trees is being planted that aims to span 8000km across the Sahara.
