DESERTS --- ENVIRONMENTAL ISSUES

THE   HOT   DESERTS --- ENVIRONMENTAL   ISSUES

The desert areas are growing in size due to a process called desertification. This happens because: land has dried up as the Earth's climate has warmed; less rain has fallen, killing trees and grasses on the edges of deserts; overgrazing of animals has meant the land has become bare; an increase in population has forced people to grow crops on unsuitable land, making it become exhausted and prone to soil erosion. As it becomes harder for people find food and water in the deserts, widespread famines and droughts can occur. In Somalia in Africa, 2 million people were forced to leave their homes and become refugees in the neighbouring country of Ethiopia to survive a drought in 2011. In Egypt, the Aswan High Dam was built in the early 1900s to provide irrigation for the local farmers and many people have built their own anti-sand shields to stop dunes from spreading.

DESERTS ---- PEOPLE

THE   HOT   DESERTS

Only 5% of the world's people live in desert areas. Many live in groups or tribes and are nomads, travelling from place to place in search of: food, water and fresh grazing for their animals. Examples include the Bushman people living in the Kalahari desert and the Bedouin nomads from Arabia. Image Credit: Edward Wachtman Others live in small, fertile areas called oases. Oases form around springs or well where people can settle permanently. In the Sahara and Arabian desert, the date palm is a major oasis crop. Its: broad leaves as used for roofs; dates are eaten as a nutritious fruit; trunk is used for building with. Many people live in round tents in the desert, called yurts. They are made by putting up felt and animal hides on a wooden frame. Desert people have learnt ways to help them survive in the desert climate - they know which plants contain water and wear long, loose clothing to protect them from the heat and dust.

DESERTS -- PLANTS

  THE   HOT   DESERTS -----PLANTS

Those plants that do grow in deserts have special ways of surviving in the dry climate with very little water: Cacti - which are only fond in American deserts - are a type of succulent plant because they store large amounts of water in their thick, fleshy stems when it rains. They have spines instead of leaves because spines allow less moisture to escape. The tallest are saguaros which can reach 15m tall and live for 200 years. Some desert plants only grow when it rains. Their seeds may lie dormant, or inactive, in the ground for years, just waiting. When rain comes, they: grow, flower and die within a few days. The century plant, for example, produces just one flower in its lifetime. Trees such as the acacia have leaves pointing upright to protect them from the intense sunlight and have developed a resistance to fire. Many desert plants have long, shallow roots which spread out over a wide area. The roots absorb any rain which soaks into the ground. Their leaves are always very small, to minimise water evaporation from their surfaces. When it does rain, deserts are often scattered with bright flowers.

DESERTS --- ANIMALS

THE  HOT   DESERTS  ---- ANIMALS

Desert animals need to keep their bodies as cool and moist as possible. Many only come out at night when the desert cools down and have special features and types of behaviour to help them live more easily in the hot, dry desert conditions during the day: carnivores like the desert fox take in moisture from the blood of their prey; many desert animals like the jerboa have long ears, which lose heat easily; the elf owl nests in the stem of a cactus; geckos have tough, scaly skins to protect them from the sun and have webbed feet to help them move across the sand; the red kangaroo can keep itself cool by licking the fur on its arms; the ground squirrel can use its large, bushy tail as a sun umbrella; termite nests point north-south so only a small area faces the general direction of the sun. There are two types of camel - a dromedary has one hump on its back and a bactrian camel has two humps. They: can drink 100 litres of water at a time, then survive for up to a whole week without another drink; have no fat under their skin to keep them cool - it is stored in their hump(s) instead; have long eyelashes and hairs in their nose to protect them from dust storms; have wide, padded feet to stop them sinking into the sand.

DESERTS ---- CLIMATE

THE    HOT   DESERTS ---- CLIMATE

Clouds hardly ever form in deserts because the air is so warm that it can hold lots of water vapour without it condensing. This makes rain very rare. The Atacama desert in northern Chile is the driest desert on Earth. Parts of the desert had no rain for 400 years, from 1570-1971, and in other parts, rain has never been recorded. With no clouds to block the Sun's rays, the ground becomes baking hot. Surface temperature of at least 40oC are not uncommon. At 57oC, Death Valley is the driest, hottest place in North America. Gold prospectors died there, in 1849, when they ran out of food and water on their way to the Californian goldfields - which is how the valley got its name. Nights can be very cold, though, and even frosty in winter, because cloudless skies let heat escape. Strong trade winds blow across the deserts. In sandy deserts, the wind sweeps up fine sand and causes dust storms up to 3,000m high. As sand is blown along, it erodes rocks in its path. Over many years, the rocks may be sand-blasted into weird, sculptural shapes. The total rain for the year usually falls in just two or three heavy storms. The water does not soak in straight away, but runs rapidly across the surface, sweeping up valley debris and carrying it along wide channels called wadis. Deep canyons may be formed too.

DESERTS ---- LOCATION AND AREAS

THE    HOT  DESERTS

Deserts are dry, barren areas where less than 25cm of rain falls each year. They are mostly located in tropical areas, between about 15o and 30o north and south of the Equator. Deserts are found in areas where dry winds blow across the land. These can be a long way from the sea, where moist sea winds do not reach (e.g. the Gobi desert in Asia). They can also be in areas separated from the sea by high mountains, called the rainshadow (e.g. the Atacama desert in Chile). Sandy deserts are made up of sand which has been blown from rock faces to form smooth hills called dunes. The Sahara in Africa is a sandy desert. Stony deserts are made up of bare stone, such as the Sturt Stony Desert in Australia, for example. In some places, such as Salt Lake City in the USA, large lakes have dried up, leaving behind a layer of salt crystals. World's Largest Tropical Deserts Desert  Location Area (km2) Sahara North Africa 9,065,000 Gobi China 1,295,000 Kalahari Southern Africa 582,000 Great Victoria Australia 338,500 Great Sandy Australia 338,500 There is little to protect a desert from the action of the wind. Strong winds pick up fine surface debris and blast it again exposed rock, eroding it away to form rock pillars and isolated hills - such as Ayers Rock (Uluru) in Australia.       The most common dunes found in sandy deserts are called barachans. They are crescent-shaped and may be up to 30m high. As sand is blown up one side and slips down the other, these dunes can creep forward between 10 and 50m a year and can engulf villages.

EQUATORIAL REGIONS ---- ENVIRONMENTAL ISSUES

ENVIRONMENTAL   ISSUES

Huge areas of rainforest are cleared each year: drug companies want to use plants to help them create medicines; developers want to build new roads and settlements; mining companies want to extract precious minerals (such as zinc, iron and diamons) and fossil fuels (such as oil and natural gas) from the ground; logging companies want timber to make paper and to build furniture with; energy companies want to construct dams and lakes for hydro-electricity power stations; farmers want more open land to ranch cattle and grow crops such as: coffee, cocoa and rubber on. Although deforestation helps countries develop and can create new jobs, some people worry that it will be bad because it will: lead to a shortage or natural resources in future; destroy the habitats of many plants and animals, possibly making some species extinct; lead to soil erosion as there are fewer roots to hold the soil together; make the ground less fertile (healthy) as nutrients can be easily washed away if there is no tree canopy; increase pollution levels with more: timber lorries, cattle trucks and petrol takers around; affect the climate. In recent years, more sustainable ways of using the rainforests have been developed to help conserve and protect them: farmers can only grow crops on limited areas of land; logging companies have to plant new trees to replace the ones they cut down; eco-tourism is being promoted where people just come to: admire the animals, go on scenic jungle tours and visit native villages.

EQUATORIAL REGIONS --- THE KAYAPO TRIBE

THE    KAYAPO   TRIBE

The Kayapo people are a tribe of about 8,638 indigenous (native) peoples who live in the Amazon Rainforest. They like to call themselves Mebengokre, meaning 'the men from the water place'. The Kayapo tribe live alongside the Xingu River in several scattered villages ranging in population from one hundred to one thousand people. They have small hills scattered around their land and the area is criss-crossed by river valleys. Their villages are typically made up of about dozen huts. A centrally located hut serves as a meeting place for village men to discuss community issues. Their appearance is highly decorative and colourful, using: face and body paint, beads and feathers. The Kayapo believe their ancestors learnt how to live communally from social insects such as bees, which is why mothers and children paint each other's bodies with patterns that look like animal or insect markings, including those of bees. Men wear the flamboyant Kayapo headdress with its outwardly radiating feathers (representing the universe) at ceremonies to mark the changing of seasons as well as rites of passage. The Kayapo people use shifting cultivation where land is farmed for a few years, after which the people move to a new area. New farmland is cleared (using cutting and burning) and the old farm is allowed to lie fallow and replenish itself. Crops they grow include: weet potatoes, yams and papaya. Since the initial arrival of Europeans around 500 years ago, the Kayapo have experienced forced migration further west into the rainforests. They have lost: land, habitat and they have also suffered from the introduction of diseases from the outsiders. The Kayapo are keen to preserve the rainforest and since 1989 they have worked with The Body Shop to raise awareness about the destruction of the Amazon. They have also been involved in protests against the building of hydroelectric dams on their land. Despite the prospects of new job opportunities and the providing of an essential power supply to the area, they argued that: entire Kayapo communities would be forced to move; huge areas of untouched rainforest would be lost; pollution from construction would damage the air quality; fish would be killed which are an important food supply for the Kayapo; diseases would be more easily spread near the stagnant water.

EQUATORIAL REGIONS --- PEOPLE

PEOPLE

Various tribes of people live in the tropical rainforests, such as: the Pygmies in central Africa, the Lumad peoples in the southern Philippines and the Amazonia Indians of South America. Whilst some are keen to trade high value forest products such as: animal hides, feathers, and honey with agricultural people living outside the forest, others prefer to remain elusive - it is believed that there are 67 different uncontacted tribes in Brazil and 44 on the island of New Guinea, for example. Different tribes of rainforest people live different lifestyles: Some are nomads, which means that they move from place to place. They chop down trees to make small clearings and then spread the ashes to make the soil fertile for a while before moving on to a new patch, in a way of farming called slash and burn. Some are hunter-gatherers, which means that they have a central camp and hunt animals and gather food from around them in the forest, such as: nuts, fruit and honey. Many people who live in rainforests find that using boats on rivers is the easiest way to travel around.

EQUATORIAL REGIONS ---- PLANTS

PLANTS

Hundreds of types of hardwood trees grow in tropical rainforests, like: mahogany, rosewood and ebony.

Rainforests are so dense that the trees have to fight for sunlight. They grow very tall and spread out their upper branches to catch more light.

The trees are adapted for living in the hot and wet climate. They have:

• flared buttress roots to help hold them up;

• waxy leaves to stop fungi growing on them and reduce transpiration (loss of water) in the heat;
• large, flat leaves to catch as much sunlight as possible;
• drip tips on their leaves to help drain water quickly when it rains heavy;

• branchless trunks to grow up quickly and fill any gaps in the canopy;
• an evergreen appearance as the continuous growing season allows them to shed their leaves at any time.

Coffee, chocolate, banana, avocado and sugarcane all originally came from plants growing in tropical rainforests.

EQUATORIAL REGIONS --- ANIMALS

ANIMALS

A diverse range of millions of different animal species live in the rainforests because there is plenty of: food, water and warmth for them. Arboreal animals that live among the branches need to be able to move from tree to tree whilst only small creatures live on the forest floor because they can move about the tangled shrubbery more easily than larger animals. Eagles sit on the branches of the tallest trees, looking for animals below who they can swoop down on to eat. Parrots have strong, curved bills (beaks) to break open nuts and seeds from giant trees. They have multi-coloured feathers to help them stay camouflaged (hidden) among the colourful blossoms of the trees. Sloths have hook-like claws to help grip the branches. They move very slowly and sleep hanging upside down. Flying squirrels glide between trees using a flap of loose skin that connects its front and hind legs. Spider monkeys have a powerful tail which they use to help them swing quickly from branch to branch. Tree frogs are light in weight and have discs at the tips of their fingers and toes to help them grasp tree leaves. Jaguars have a dark, spotted body so that they can creep up on and ambush prey without being seen. To kill, they bite directly through the skull between the ears and into the brain. Chameleons can change the colour of their skin to help them camouflage (hide) from any predators. They also have long tongues that can flick out and stretch up to twice their body size to catch insects. Howler monkeys make lots of noise to tell each other where they are in the gloomy forest floor. They are the loudest land animal in the world and their growls can be heard clearly for 20 miles. Tapirs are active at night and they have a long snout to pull food into their mouth, such as fallen fruits and nuts. Leafcutter ants cut out tiny pieces from leaves and carry them back to their nest. Weevils like to feed on the decaying wood of fallen tree trunks.