Hot Deserts Geography Paper 1 GCSE

From Living World

The interdependence of desert climate, water, soils, plants, animals and people

The living things that inhabit hot deserts are linked to each other and their physical environment. Many of the elements of the biome are interdependent upon one another. People are dependent upon their animals in deserts, for food, milk and as use as pack animals. For example, the Beja people use camels in North East Africa through Sudan, Egypt and the Sahara Desert. While plants rely upon soils for their nutrients, the soils rely upon plants to provide extra nutrients through dead vegetation and fixing chemicals from the air into the soil. Plants also help soils retain more water, by providing shade from the desert sunlight. Plants also tie the soil together, preventing soil erosion and excessive leaching of nutrients in wetter periods. Oases exist in low points in the desert, where water can be found closer to the surface and some agriculture is possible.

Desert Plant Adaptations

• No leaves or small seasonal leaves that only grow after it rains - this helps reduce water loss during photosynthesis.  These plants conduct photosynthesis in their green stems.

• Plants can store water in their stems or leaves, these are called succulents;

• Many plants have long root systems spread out wide or go deep into the ground to absorb water;

• Short life cycles - some plants germinate in response to rain, grow, flower, and die within one year.  These plants can therefore avoid drought.

• Leaves with hair - these help shade the plant, reducing water loss.  Other plants have leaves that turn throughout the day to expose a minimum surface area to the heat.

• Spines to discourage animals from eating plants for water;

• Waxy coating on stems and leaves - this helps to reduce water loss.

• Many plants are slower growing – this requires less energy.  The plants don't have to make as much food and therefore do not lose as much water.

The cactus shown below is well adapted for survival in the desert.  They have many of the features listed above.

Desert Animal Adaptations

Animals also have to cope in the desert, using adaptations such as being nocturnal or living under ground to survive.

Camels often live in deserts that are hot and dry during the day, coping with wind-blown sand and cold at night. They are well adapted for survival in the desert. Camels have:

• Thick fur on the top of the body for shade, and thin fur elsewhere to allow easy heat loss.

• Large surface area to volume ratio which maximises heat loss.

• Large, flat feet to spread their weight on the sand.

• The ability to go for a long time without water  -  they lose very little through urination and sweating.

• A fatty hump which provides energy in times of food shortages (they don't store water in their humps).

• The ability to tolerate body temperatures up to 42°C.

• Slit-like nostrils and two rows of eyelashes to help keep the sand out of their eyes.

There are considerable threats to biodiversity in Hot deserts including;

climate change – changing rainfall patterns and increased frequency and intensity of droughts threaten the delicate ecological balance as water becomes more scarce.

wildfires – slow-growing shrubs and trees will be replaced with faster-growing grasses, altering the ecosystem.

overgrazing, over-cultivation and logging for firewood destroy vegetation, exposing the soil to erosion by rain and wind, leading to desertification, especially on desert fringes.

desert tourism – off-road vehicles damage vegetation and disturb wildlife.

The extreme nature of desert environments means that plants and animals must adapt to survive. Plants and animals are regularly exposed to extreme temperatures and drought conditions.  They must also cope with extensive water loss.

Opportunities of development in hot deserts, the Western Desert

The western desert has an abundance of valuable minerals such as copper, lead, zinc and coal.

The Sonoran desert has had lots of copper mining for 100s of years which was small scale but because water supplies were discovered below ground has allowed large scale open cast mining to take place.

Other commercial activities such as tourism and farming also exist in the Western desert so some minerals haven't been fully exploited.

Uranium mining was stopped after indigenous people had a campaign about the risks to both water/land contamination and wildlife.

Lots of sun so good for a solar farm to generate electricity

Vast open space so the landscape is exposed with no geographical barriers such as forests to reduce wind speeds so wind energy can be harnessed really well

Colorado river can provide hydroelectric power from the Hoover Dam

Lots of fossil fuels so there can be oil drilling, this also provides lots of jobs

Lots of sun makes it suitable for agriculture and water supply can be managed by investing into irrigation using aquifers and canals. 80% of Colorado's water is used for agriculture even though it contributes only 10% of the economy.

Opportunities for tourism such as; National parks such as Grand Canyon, Las Vegas, Lakes Mead and Powell which is a fishing and sailing touristic hotspot.

Challenges of development in hot deserts, the Western Desert

Low population density such as harsh conditions for Native Americans. This is because places such as death valley in the Mohave desert are inhabitable for humans as temperatures reach 50 degrees in the summer. People live around rivers and aquifers so expansion into the desert is limited.

Inaccessibility leads to a lack of infrastructure development such as few roads and almost no shops/mechanics/fuel stations on the road. Breaking down can be fatal. When roads are ok extreme heat makes driving dangerous.

Las Vegas has a lot of infrastructure including an airport as it was historically a good place for a train station and shops, hotels and industry built around it.

Intermediate technology or appropriate technology

 Technology that is suited to the needs, skills, knowledge and wealth of local people in the environment which they live.

Over-cultivation

Exhausting the soil by over-cropping the land.

Overgrazing

Grazing too many livestock for too long on the land, so it is unable to recover its vegetation.

Soil erosion

Removal of topsoil faster than it can be replaced, due to natural (water and wind action), animal, and human activity.

Subsistence farming

A type of agriculture producing food and materials for the benefit only of the farmer and his family.

The causes of desertification

Desertification is the process by which land becomes drier and degraded, as a result of climate change or human activities, or both.

It is caused by a mixture of climate change and the issues raised by population pressure. As population increases they increase the numbers of animals they keep, such as goats, which eat more vegetation. They also farm the land more intensively, which extracts nutrients and removes the natural vegetation. People also collect more firewood to keep warm at night or for cooking. In addition, Climate change is making temperatures hotter and rainfall less reliable and more variable. All of these things reduce the amount of natural vegetation. There are no plants or leaves to intercept rain and soil is left exposed to hot sun so the sun bakes the soil and it cracks. When it rains, the rainwater runs over the surface of the soil rather than soaking in which means that soil can often be washed away. This means that the soil is degraded; losing fertility and structure. This completes the cycle, as even less vegetation can be supported and the environment declines further.

The effects of desertification

Desertification is a serious issue that affects over 1 billion people around the world. It can have a damaging impact on both people and the natural environment. In 2014 the UN stated that 20million people in the Sahel region of Africa faced hunger and required $2 billion in food aid due to desertification.

The loss of vegetation can cause severe soil erosion. The nutrients in the soil get washed or leached away leaving soil infertile. The loss of vegetation also means that there has been damage to animal’s habitats. In addition, loss of species affects the availability of local medicines. Population pressure has also stopped people moving animals from place to place as they traditionally did and using settled agriculture. This settled agriculture means that people farm too intensively which also drains the soil of its nutrients. This leaves the soil of poor quality where nothing can grow. This leads to regular crop failure. People also draw more water out of the soil for irrigation. Together with the drying of the soil this leaves deposits of salt (Salinisation) and means crops can’t be planted. Lack of food and water can also mean farmed species such as cattle can die of starvation.

People have to migrate out of these desertified areas and often end up in shanty towns at the edge of big cities or in refugee camps. Food aid can be flown in but people can become reliant upon this. However, famines do happen and 250,000 people died in the Sahel drought of 1968 to 73. Desertification also means there are less tree cover and more grasses, which protect the soil less.

Strategies used to reduce the risk of desertification

Desertification is not inevitable and with careful management of water resources, the soil and vegetation via tree planting we can limit the spread of deserts. We have even managed to reverse the effects of desertification. Many of the techniques used have used appropriate technology, which is suited to the needs, skills, knowledge and wealth of local people in the environment which they live.

Tree Planting in Senegal

In the Senegal region of the Sahel (a 5,000km long belt of land that separates the Southern part of Africa from the Sahara) the Food and Agriculture Organisation (FAO) of the UN is trying to help in the fight against desertification. Less than 50 years ago land in this region of the Sahel was productive Savannah, but is now dry desert because of decades of climate change and over intensive farming, forestry and land degradation. This has led to vegetation disappearing.

A project focusing on Acacia or gum trees is trying to help. The FAO and forestry service have provided nursery’s to grow seeds and seedlings. The locals were also taught how to sow and plant the Acacia trees, and how to extract and market the gum they produce.

They were also given a tractor and digger tool specially adapted to dryland conditions. It cuts half-moon shaped holes which collect rainwater ensuring that the young plant roots will have enough water to survive the long dry season. This also massively reduces the amount of labor needed.

Planting the trees reverses desertification by preventing soil erosion and providing nutrients for other plants and crops to grow. The tree is a native tree, it puts nutrients back into the soil, provides shelter for crops under its branches and provides fodder for livestock.

The knock on effects have been good for the whole community.

The Great Green Wall

The Great Green wall is a planned project to plant trees across Africa along the southern edge of the Sahara Desert to prevent the desert spreading south. It has been developed by the African Union to reduce the negative effects of desertification and land degradation on people, the environment and the economies of the countries affected.

Stone lines - water and soil management

Desertification leads to outmigration in countries such as Burkina Faso in the Sahel. This idea was to lay stones along the contours of the land in long lines which traps the rainwater that falls. A contour stone line 25 to 30cm high with other stones behind is constructed. These stones slow down run off water and allow it time to infiltrate the ground and rich sediments to be trapped in the field. This results in less erosion and more water for the crops.

Farmers were trained in laying out contours using a simple water tube level. They marked out the contours and dug out a foundation trench. Large stones are then placed into this trench followed by smaller ones. Grasses can also be planted along the barrier. The villagers work together and it is a collective effort. The technique has spread from Burkina Faso to Mali and Niger. It is a technology that is low cost and requires skills that can be quickly learned.

Planting pits are also used to hold more water around the plant and homemade compost is used to provide a fertility boost for the soil. Barren land has been restored and vegetation re-established so the scheme has been a big success and sustained.