Background
The Sahara
The Sahara has not always been just sand. Millions of years ago, it was a green and pleasant land. But over the centuries, wind, sun, heat and lack of rain turned it to sand. Desertification had struck.
The Bedouin manage a nomadic but sustainable life, as long as there is pasture to graze the animals (goats and sheep) on which they depend for food and drink. They live in sophisticated tents which can be packed up and moved by camel as soon as the pasture is grazed.
For thousands of years the Bedouin have known how to find exotic riches like frankincense and myrrh, but above all, they know how to find the most precious thing of all: water, when all that anyone else would see is sand.
But life for nomads is getting harder.
The Tuareg have a strong culture, which is unique: their own language and alphabet and a fearsome reputation for independence. The continuing drought has meant that some Tuareg are being forced to abandon their nomadic ways and move to cities to find food. Meanwhile, those who remain in the desert are having to give up travelling and build irrigation systems in order to survive.
The development of southern Spain
A thousand years ago, Arabs from Morocco settled in southern Spain, bringing with them the desert culture of the Middle East. They developed ways of watering the hot, dry land, as they still do in North Africa.
Cleverly built aqueducts collected rainwater, which was stored in cool stone vaults. It was then metered out along irrigation channels to crops, which blossomed. For six hundred years agriculture flourished. Farmers were taking what the land could give and not abusing its fertility.
In the end, the Spanish Christians wanted the whole of Spain. After a long war, the Arabs were finally expelled at the end of the fifteenth century, and they took their knowledge with them. Their farming ways were slowly forgotten, woods and forests were cleared, and water resources were over-exploited.
The Mid-West, USA
When native Americans roamed the Mid-West, hunting bison and gathering wild rice and herbs, the land was left unharmed. There was plenty of it, and it had never been ploughed.
Where only buffalo had grazed, the newcomers cultivated what became huge farms to provide wheat and beef from the vast, rugged area between the Rockies and the Appalachians.
Every year, cool dry air blowing from the north meets warm moist air from the south. The result is tornadoes: twisting winds that suck everything up into the atmosphere, ravaging the soil and wrenching it from farms.
When desertification struck in the 1930s, the weather made the situation worse.
Some farmers still remember it as the worst time of their lives. They had taken the land for granted, and now they could not grow anything.
The recovery programme was paid for by the American government - just in time, as it turned out, to feed the armies of Europe fighting the Second World War.
The droughts of the 1980s, though, were so bad that even the new agricultural methods were not sufficient to save farmers from being ruined.
The native Americans tried an ancient method - rain dances - but without success. There was talk of diverting the great Mississippi river, to irrigate the parched land, but the drought had affected it too. It was at its lowest level in living memory, and vital cargo-carrying barges were unable to travel on it. Global warming
Normally, the Sun's rays heat the Earth and the heat gives off infrared rays. Many of these don't escape because the atmosphere traps them, and so the Earth is a comfortable place to live. But now, power stations and cars send carbon dioxide into the atmosphere. This pollution means that fewer infrared rays escape from the Earth. This "global warming" is changing the climate and causing droughts to happen more often.
