Take up 20% of the Earth's surface (climate change/desertification)

30ºC north and south of the Tropic of Cancer and Tropic of Capricorn

• On the coast
• Wind blows over land and this looses its coastal water

HADLEY CELLS

• Moist, warm air rises over the equator, it rises, cools and turns to rain (convectional rainfall)
• The air hits the stratosphere then gets pushed to the north and south
• Sinks as very dry air (no precipitation) (constant cycle)
  

Explanation to this with images

• Can become dangerous to people's health
• Difficult to cook
• Difficult to build (temperatures and things like concrete need water)

• Difficult to concentrate in extreme temperatures
• No one will want to work strenuous hours in uncomfortable temperatures

• The Sahara’s rainfall is unpredictable and very low – no more than 70mm in some places
• Most rivers only flow for part of the year, so getting access to enough water all year round is difficult
• Most settlements in the Sahara don’t have running water or electricity – it is too remote and too expensive to set up
• Since 1969, water stored under Morocco has been used up for mining and farming. The underground lake (aquifer) has lost 1.5m of water every year since 1969

• Daily temperatures can range from over 40ºC during the day to below freezing at night – working in these temperatures can be dangerous
• The hot season is often too hot for tourists so work and employment in the tourism industry is seasonal – doesn’t last all year round
• Physical work is difficult in high temperatures, so mining and farming can be restricted to certain times of year and certain times of the day

• Providing services such as medical care is difficult in areas where there are no roads
• It can take 5 days by truck to transport salt from salt mines in Mali out of the desert – that is a long time!
• Lots of pipelines have to be built to transport products e.g. oil and gas from and to remote areas. This is very expensive.
• As the Sahara Desert is so big, with very few roads, people, products and materials have to travel long distances, often by air which is very expensive

Extreme temperatures make it difficult and stop people making money because, it would be difficult to concentrate, working outside would be uncomfortable and difficult

Limited water supply would make life difficult as builders and construction workers won't want to work in 50℃ heat, this is hard labour and uses large amounts of energy, this means they will become dehydrated and this could endanger their health

Inaccessibility can make life difficult as there are barely any roads (people can't access or afford cars), there are no forms of public transport and people can't walk everywhere

• 40% of the food we consume is imported (this can be because of growing conditions (mangos, bananas) or because we want food that isn't in season)
• Irrigation is happening and this can waste water
• 500 litres of water to grow 1 kilogram of potatoes

• Food choices all year round
• 400,000 tonnes of potatoes are exported to the UK each year (provides jobs for farmers, pickers etc, this means they pay taxes, quality of life improves and they are provided with healthcare, education etc)
• Money from exports (taxes)
  

• Food miles (rather than growing them i the summer and storing them correctly, we import them and present the challenges of CO2)
• 500 litres of water to produce 1 kilogram of potatoes
• Using these aquifers rapidly (once they are gone, they are gone)
• Potato pickers have poor pay and is very physically demanding

This is an 8,000 km wall of Acacia trees are being planted on the walls of Africa and this is planning to stop the expansion of the Sahara and desertification

• Stopping the Sahara from spreading
• 7 kilometres thick
• 11 million trees (carbon sink)
• Tree roots hold water (the crops will then get the water that is on the soil)
• Former dry wells are being replenished naturally (frees women and children (they are travelling to a closer place and can live a more fulfilled life) and this clean water helps reduce water related diseases (cholera etc), this clean water is helping their economy, by not spending money on these diseases and healthcare and by being ill from water diseases, they are too unwell to work on their farms (subsistence farmers), this means their families wouldn't eat)
• Trees provide leaf litter and this provides nutrients that are put back into the soil, these nutrients mean that other crops and vegetation can grow
• The canopy increases

• Costs 8 billion to build
• Very long and time consuming to build (effects won't be seen immediately)
• Many countries aren't planting the trees (1/11 countries have done it, only Senegal)
• Trees take a long time to grow

Hose pipe system that is entered underground that means no water is lost via evaporation

• No water is lost (the water needed is given, this means they are not overwatered, no water is lost by evaporation, the water goes straight into the soil so it is taken up by the roots, use less water but the farm is the same size)
• Cheaper to install
• More sustainable (grow there for longer and makes the soil more fertile because of more crops growing)

• Initiacial costs are high (subsistence farmers are unable to access these)
• Not accessible for everyone

Low cost, Local people, Low tech
Work out the contouring (hilliness), and put down stone, this traps the water and nutrients

• Easy to do (don't need maintenance (the occasional check up))
• Local people do the work and can teach each other (use simple models which means it is cheap and easy, local people can then water their crops and this can speed the growing process)
• They can plant crops immediately (subsistence farmers can immediately start filming their families and may have extra to sell and make them money)

• Only works in semi-arid deserts (wouldn't work in Sahara)
• Some wouldn't want to get involved and get on board (makes the process slower and harder)
• Manual labour

Only work in semi-arid deserts as they get a more sustainable amount of rainfall