Deserts are extremely dry arid places True deserts

• Deserts are extremely dry (arid) places. • True deserts normally have less than 250 mm a year, although some deserts like the Atacama to the right can go years without any water. • Deserts are very dry because the air that descends over them is very dry

• • The air is dry because most of the moisture has fallen as precipitation over the Equator (tropical rainforests) before being pushed out and falling near the tropics. The air is also very dry because the air travelling from the equator to the tropics travels over land not the sea. This means that no additional moisture is picked up. Because there is no moisture in the air, there are very few clouds in deserts which means desert areas are exposed to high levels of incoming radiation from the sun. This means that daytime temperatures in the desert are very high. However, the lack of cloud cover also means that a lot of outgoing radiation is able to escape, making desert temperatures very cold at night presence of high pressure creates cloud-free conditions mountain ranges create RAIN SHADOWS

NO CLOUDS!!!!

Succulents e. g. cacti: Succulents tend to be fairly fat fleshy (carnoso) plants that are able to store water in their leaves, trunks and roots.

Ephemeral: These are plants with very short life cycles - typically 6 -8 weeks. This means that they can take advantage of very short wet seasons in order to pollinate. desert plants that grow, flower, and set seed in brief periods of rain. then came back in a more or less long dormancy phase.

Long and wide roots: Plants in deserts have very long roots so that they are able to absorb the maximum amount of rainfall during periods of rainfall. It also makes them more stable in very lose soil. Shallow enaugh to reach the water of rainfall

Spiky (spinose) and waxy (cerose) surface • Many plants like cacti protect themselves with spikes and wax so that they are not eaten or damaged by animals. • Lustrous, shiny leaves are not only visually attractive but have a practical purpose. • Plants often grow a waxy coating as protection against certain environmental factors. • Waxy coatings are barriers between the leaf and the environment, and they can help the plant retain moisture in hot environments. • The coatings can also deflect the rays of the sun to keep the plant from transpiring too quickly, and may also discourage pathogens, like fungi and bacteria, from entering the leaves.

Succulents e. g. cacti: Succulents tend to be fairly fat fleshy (carnoso) plants that are able to store water in their leaves, trunks and roots. Ephemeral: These are plants with very short life cycles - typically 6 -8 weeks. This means that they can take advantage of very short wet seasons in order to pollinate. Long and wide roots: Plants in deserts have very long roots so that they are able to absorb the maximum amount of rainfall during periods of rainfall. It also makes them more stable in very lose soil. Spiky (spinose) and waxy (cerose) surface: Many plants like cacti protect themselves with spikes and wax so that they are not eaten or damaged by animals. Lustrous, shiny leaves are not only visually attractive but have a practical purpose. Plants often grow a waxy coating as protection against certain environmental factors. Waxy coatings are barriers between the leaf and the environment, and they can help the plant retain moisture in hot environments. The coatings can also deflect the rays of the sun to keep the plant from transpiring too quickly, and may also discourage pathogens, like fungi and bacteria, from entering the leaves.

Which animals live in the desert? Animals in the desert must survive the intense heat, searing sun, and lack of water. Animals that live in the hot desert have many adaptations. Some animals never drink, but get their water from seeds (some can contain up to 50% water) and plants. Many animals are nocturnal, sleeping during the hot day and only coming out at night to eat and hunt. Some animals rarely spend any time above ground.

THE THORNY DEVIL DRINKS WITH ITS SKIN. The thorny devil has developed skin that can absorb water like blotter paper (carta assorbente) (called “capillary action”). The way the scales (squame) on the body are structured, it collects dew and channels it down to the corners of the mouth.

Big Ears Act Like Radiators. The fennec fox of North Africa • has large ears which serve a dual purpose: • they are great for listening for bugs (insetti) to eat that may be moving around underground; • they are also loaded with blood vessels, allowing the animals to dissipate excess body heat. • While big ears are wonderful radiators during hot days, the fox’s thick fur coat also acts as insulation during cold desert nights.

The Camel Is a Living Desert Adaptation. The hump stores fat, which can be used as both a food and water source. Camels also have thick hairs in their ears for keeping out sand, and the same can be said of their eyelashes wide feet that act snowshoes in the sand. like

Scorpions Can Slow Their Metabolic Rate, allowing them to “Hibernate” While Awake.

Some of the animals that live in the desert. A sidewinder is a small agile snake. It is mainly nocturnal and takes shelters from the heat of the day in the burrow (cunicolo) of another animal or under a bush. The fat sand rat overcomes the problem of the unpredictability of desert food supplies • by laying down a thick layer of fat all over its body when there is plenty of food It then lives off this fat when food is short. • Active day and night, collects seeds which it carries back to its burrow.

Human Threats • Even though deserts are very hot arid environments that normally have very low population densities, humans can still threaten them. Some of the threats caused by humans include: • Extraction of resources e. g. copper (rame) in the Atacama Desert • Hunting e. g. Oryx (antilopi) and Cheetah (grandi felini es. ghepardi) in the Namib Desert • Tourists damaging dunes e. g. dune boarding and desert bashing (gara di fuoristada )in the Arabian Desert • Overgrazing killing what little vegetation there is and overcultivation e. g. Southern Sahara • Deforestation: There is limited vegetation in deserts, but often it is removed for fuel or to make space for crops • Toyotarisation: 4 X 4 vehicles being driven across the desert disturbing animals, killing vegetation and creating dust storms

Physical Causes of Desertification • Rising Temperatures: As global temperatures increase it is becoming increasingly hard for vegetation to grow thus reducing vegetation cover and increasing the risk of wind and water erosion. • Falling Rainfall: As the amount of rainfall reduces in some areas like the Sahel, then it is increasingly hard for vegetation to grow again making the ground more vulnerable to wind and water erosion. • Flash floods: Intense periods of rainfall can also cause erosion of topsoil which leads to land degradation. • Wind: If a region is particularly windy then the amount of wind erosion is likely to increase.