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What is a desert

What is a desert

[A desert is] a water-controlled ecosystem with infrequent, discrete and largely unpredictable water inputs. [I Noy-Meir, 1973]

Imagine a world where water is in such short supply, and so unpredictable, that it determines the pattern of life. Not just across the landscape, or through the cycle of a year, but across a decade, a century or a millennium. Deserts are difficult places for people because of their aridity, their unpredictable ecology, and also because they are patchy environments where food, water and plants are often concentrated in small pockets.

Three ways of desert living

How you live in a desert is important if you expect to be a long term resident. One response is to be highly mobile and opportunistic. Another way is to use your social networks to escape the constraints of the environment. Some desert communities have grown rich, trading with outside groups. Or you could invest heavily in technology and infrastructure, to harvest or move water, or to store water and food to buffer the hard times.

What is a desert?

From left to right:

Leslie Stafford, extracting honey from a tree, Central Australia. Photo: George Serras, National Museum of Australia. Harvesting !nara melons, !Khuiseb River, near Walvis Bay. Photo: Wilfrid Haacke. Pascualina Mamani, Rio Grande, Chile, cultivates onions, carrots and garlic which she sells in Calama. Photo: Guy Wenborne.


Acknowledgements
I Noy-Meir, 1973 . 'Desert ecosystems: Environment and producers', Annual Review of Ecology and Systematics, 4, 2551.

Perishing in the desert

To perish

How long would you survive? In the desert, in 38 degrees Celsius heat, without water or shelter, dehydration will kill most people within a couple of days. Few would survive a week.

How long would you survive in a desert? And if you had a choice, which desert would you choose? Not all deserts are barren rock and shifting sands. Some, like the Australian desert, are a sea of spinifex and acacia shrubs. But all deserts are uncertain places, often with long dormant periods between pulses of life. The people of the southern deserts have ridden out the boom and bust of desert environments for millennia, and created distinctive ways of living. The risks of getting it wrong are shown by the stories of explorers and travellers who perished.

The elixir of death

In 1874, explorers Ernest Giles and Alf Gibson pushed deep into the Australian desert. When one of their horses died, Gibson rode on ahead, and perished. Alone, Giles walked for seven days carrying a few litres of water. 'I became so thirsty ... that I longed to drink up every drop of water I had ... but it was the elixir of death ... to drink it was to die.' Giles walked at night, eked out his water - and survived.

What happens to your body in the desert?

The human body's margin of survival is dangerously thin. You spend your entire life less than 5 degrees Celsius away from fatal overheating. Although the human body is designed to endure the heat far better than the cold, no one can survive the burning heat of a desert sun, and no one can live without water for an extended period of time.

In desert heat, you sweat to regulate your body temperature. This is an effective method of cooling, but unless you drink water, sweating will kill you. Two-thirds of the human body (or 50 litres) is composed of water. Lose 1 litre and your body's functions become impaired. Lose 5 litres and fatigue and dizziness set in. Lose 10 litres and vision and hearing are impaired. Lose more, and the consequences can be potentially deadly. Sweating fails and your blood becomes a salty sludge. Internal organs overheat. Your kidneys no longer filter the thick blood. Muscles spasm. You become confused as your brain chemistry is disrupted. Cells swell and burst, triggering a cascade of fatal damage.

Acknowledgements
Giles, E 1964 [1889]. Australia Twice Traversed, Libraries Board, South Australia, p.39.
Kamler, Kenneth 2004. Surviving the Extremes, Hodder, Sydney.

The first desert people

Today, four million people live in the southern deserts. When did people first moved into such extreme places, and how did they get there?

At some point, people arrived in each of the deserts, stepping out across land that until then no human had ever visited. No one knows for sure what these pioneers looked like, but rock art and stone tools give clues about their way of life. People arrived in southern Africa's Namib and Kalahari deserts 300,000 years ago. In both Australia and South America, moving into the desert was part of settling a new continent. By 30,000 BP, people were living in the Australian desert, and in the Atacama by 11,000 BP. In the Extremes exhibition you can see artefacts that represent the earliest traces of these people.

First traces in the Namib, 300,000 years ago

The gravel plains and hills of the southern Namib Desert preserve the earliest traces of people living in the southern deserts. Hunters followed game and water into the Namib about 300,000 years ago, wherever springs and floodwaters provided an accessible route into the desert. Hand-axes and the bones of elephants and buffalo are found in ancient campsites along the Tsondab, an old river channel now choked off by dunes.

Australia: Settling a desert continent, 30,000 BP

The boom and bust nature of the Australian desert provided the opportunity to move into the desert almost as soon as people reached its borders. The real problem was staying there, when the hard times returned. By 30,000 BP, small groups of highly mobile hunter-gatherers were using pockets of country across the interior of the continent, from central Australia to the Pilbara, and from Lake Mungo to the southern Kimberley.

From the mountains into the Atacama, 11,000 BP

As soon as the glaciers retreated, hunters moved into the Andes mountains. They followed the puna (extensive grasslands) south into the Atacama region, then dropped down into the deserts on either side of the Andes. The pioneers found a desert with better summer rainfall than today, and some grasses and shrubs. In summer, people lived in the high country, hunting guanaco, deer and guinea pigs. In winter, they moved down the quebradas (ravines) to the desert floor.

Uncovering deserts past

Archaeologists have worked hard to reconstruct the human histories of the southern deserts. In Extremes you can see some of the key archaeological finds.

Some items are easy to understand, like the pots, baskets and tools used by farmers. Others, such as stone tools, small pieces of pottery, beads and red ochre, need a bit more imagination, but are just as important. You need to remember that some are only parts of larger artefacts. Archaeology is a forensic science; it is not just 'art history with a shovel'. Small clues are usually more important than beautiful objects.

Uncovering deserts past - 3 photos in 1 image

From left to right:

The famous rock paintings at Taira, Río Loa area, AtacamaDesert, Chile. Photo: Mike Smith, National Museum of Australia. Farmer's sandals and pouch with feathers, Chiu Chiu, Atacama Desert, Chile, about 1000-1400 AD. Photo: George Serras, National Museum of Australia. Archaeological dig at Puritjarra rock-shelter, Central Australia, May 1988
Photo: Mike Smith, National Museum of Australia.

While browsing through the Extremes website, and  in the exhibition, you can see that some dates are given as 'BP'. This means radiocarbon 'years before present'.