Tibet.

The flight from Kathmandu to Lhasa, past Everest and its cousins, must be the most spectacular in the world. Carved into the landscape beneath, the geological past is as easy to read as a book: two continents crash into each other, waves of percussion take form in rock, the bed of a sea is squeezed up until it becomes the planet's highest plateau on which little puddles of sea remain in the form of vast and salty lakes. It is from this "roof" that most of Asia's great rivers tumble, including the Yangtse and the Yellow.

From here the steppes and deserts of Central and Inner Asia stretch north to the mountains of Mongolia and beyond to the Siberian taiga, forming the largest natural pastureland in the world. Its grasses clothe most of the Tibet Autonomous Region (TAR) and four other Chinese provinces--the "Western regions" where China's ethnic minorities are concentrated.

Past the glass-sharp peaks, the "hills" of the plateau look like tawny velvet thrown over bones. Some are dusted with summer snow. The Yarlung Tsangpo River (Brahmaputra), must be at least two miles wide, swollen by seasonal rains, its opacity representing millions of tons of mountain, worn and torn down by water. Along valleys, there are tiny pockets of arable land containing the only grain that will thrive at this altitude--barley. There are minute, walled plantations of willow and poplar on the banks of the river. Higher than that, not a tree to be seen. That arduous, wind-battled niche belongs to nomadic herders. I have come to witness for myself one of the last great examples of a way of life once common in many regions of the world. From what I have read, Tibetan pastoralists have escaped the bleak future facing nomads in other countries, because at this altitude, and in this astonishingly unpredictable and ferocious weather, they have no competitors.

The origin of pastoralism has been much debated. Some scholars, assuming the superiority of settled cultures over nomadic, believed it to be an evolutionary stage in human progress, wedged between hunting-gathering and agriculture. But recent archaeological data suggest that agriculture actually preceded it. Perhaps proto-farmers selectively bred wild animals, and when their herds grew too large to graze locally, some took to nomadic pastoralism. Or perhaps early nomads managed wild animals, much as reindeer-herding Sami still do in regions of the sub-Arctic. Probably different forms developed frequently and spasmodically across different environments, with different domesticable species. But no one knows for sure. Nomads don't leave much material evidence behind them.

Livestock provide fresh food on the hoof: that is, it keeps from spoiling until needed. Secondary products--milk, yogurt, cheese, fertiliser and fuel--can be bartered with farmers, a trade that must have lubricated the interface between settlement and nomadism, leading to a somewhat symbiotic relationship, but with ancient suspicions built in. Nomads outside city walls can always turn to raiding. And from the other perspective, small bands of herders are usually no match for punitive armies.

However you imagine its origins, pastoral nomadism put to use the intimate knowledge hunters had of animals. Herders continued to rely on those first principles that humans had developed throughout their history--observing, learning from and accommodating themselves to the natural world. Ultimately, pastoral nomadism provided an alternative to the sedentary cultures of agricultural and urban societies.

Here on the Tibetan Plateau, it was made possible by the domestication of wild yak. Later, horses, sheep and goats were included, making for complicated mixed herding methods, with different animals requiring different pasture, and grazing at different bands of altitude.

Effective management requires constantly moving the herds to the best pasture possible during the short summer growing season. The animals must lay down enough fat in those few months to survive the plateau's appalling winter and a grim starvation spring. To accomplish that, a herder requires tremendous skill and knowledge.

Before the Chinese takeover, nomads were ruled by Buddhist lamas, in a quasi-feudal estate system. They owned their own herds, and whatever products they didn't consume themselves were bartered for barley and tea. Family members jointly managed their animals, without interference from the lamas, who, in return for tax revenue, mediated disputes and provided religious services. The nomads couldn't graze their herds wherever they chose, but individuals could travel freely and pilgrimage was an important part of social and spiritual life. There was class mobility too--anyone could enter the nobility through government or military service, and anyone could embark on a religious career. Sometimes pastoral nomads increased income by trading--travelling to Ladakh, Nepal, India, China and Mongolia. Tibetan society was a mediaeval melange of nomads, traders, farmers, hunters, bandits, merchants, monks, nuns, pilgrims and artists, united in the main by Bon-influenced Buddhism.

Modernity arrived in October 1950, when the communist Chinese Army marched into Eastern Tibet. The occupation was initially orderly, but chaos followed soon enough, ultimately resulting in over a million Tibetan deaths, the destruction of thousands of monasteries and temples, and the flight of the Dalai Lama to Dharamsala in India, where the Government in Exile now resides. Hollywood popularity and audiences with Bill Clinton notwithstanding, the chances of a "free Tibet" are vanishingly slim, and the Tibetans remaining in their "land of snows" make accommodation with the new dispensation as best they can. There is no doubt that some are materially better off than ever before. The problem is that those most benefiting are necessarily the most deracinated. The values of Chinese communism (atheism, materialism) do not mix well with the values of Buddhism. And a unique interpretation of Buddhism is at the very heart of Tibetan civilisation and identity.

It was during the Cultural Revolution, from 1966 to the '80s, that the nomads (like everyone else in China) suffered the most. Religion, so central to their identity, was banned, practitioners persecuted, and the private ownership of livestock was replaced by people's communes. All the traditional grazing structures were dismantled, and for the first time the grasslands felt the bite of the plough. That era was an ecological, social and moral catastrophe.

It ended with the ousting of the Gang of Four. Then under Deng Xiaoping's leadership, modernisation replaced class struggle as China's dominant propaganda. The communes were dismantled; livestock was returned to family ownership. Since then, meat has become popular with China's burgeoning middle class, cashmere wool is selling well on the international market, and the expanding towns of new Tibet provide local markets for livestock products.

Pastoralism has recuperated to such an extent that the nomads of the Tibetan region are doing pretty well.

That, as I say, is what I have read.

The Chinese-built road from the airport is impressive. Where once pilgrims limped into the capital after many trials of will, I am swept towards my goal at a swift post-industrial clip, in a brand-new Land-Cruiser. A centuries-old nunnery flashes by the left window; a cliff where Guru Rinpoche impaled a daemon zips past the right. The road is a strip of modernity through previous time.

Lhasa is no Shangri-la, certainly, but there are wide streets, VW taxis assembled in Beijing, gimcrack apartment blocks--all the crassness and glitter of an opportunistic materialism let loose on the frontier, but no worse, and in some ways better, than many developing Asian towns. It is clear what the employment opportunities will be. Tourism, construction, small businesses, government jobs from which to pocket a retirement fund of corruption money, and crime. It is also immediately apparent that most of the jobs are taken by immigrant Han Chinese, fallouts of China's new economic policies, who have come to the borderlands for certain perquisites available there. They will work hard, save their cash, and return to their provinces as soon as they can. In Lhasa they outnumber Tibetans by two to one, and there is no love lost between the communities.

My plan is to attend a horse festival on the Chang Tang Plateau, a couple of hundred miles north of, and a thousand or so metres higher than, Lhasa. I'll take as many days as I like getting there, camping with different nomad families along the way, or spending night-halts in nunneries.

The jeep is booked and so are my driver, A-den, an ex-nomad, and my translator, Tenzing. We head out before dawn the next day.

Sunrise clips the tops of hills, and the clouds are just as Tibetan embroidery artists depict them--curly, with a tail. The light is blinding, even at this hour, and the shadows as sharp as blades. It is so hot along the road that we keep the windows open wide, but to our right, just a hundred yards away, a snow flurry whitens the slopes.

We stop at a little "restaurant"--a tiny room, grimy and gloomy, low tables and chairs, flasks of Tibetan butter tea, and a big television set showing DVD Chinese soaps. The street is churned-up mud. The weather has turned bleak and bitter, with tattered snow clouds driven along the sky. We are enjoying the balmy delights of high summer--that window of weather opportunity in which grasses and herbage can grow. Nomads are playing pool on tables set out in the street. Their physical beauty is matched by their sense of style--cowboy hats over plaits, full-length black coats, boots and white shirts. Others, their plaits tied up in red silk tassels, squat nearby selling chunks of yak that they cut from a carcass. We buy very good sirloin. (Yak meat, tsampa (barley flour) and buttery tea are what we will live on from now on.) All the little towns are more or less the same. The ubiquitous pool tables are there in the muddy streets, surrounded by handsome nomads. Some have a wild alcoholic look in their eyes. Eventually I ask why they aren't out with their herds, or working.

At first my companions are careful what they say. Everyone assumes that everyone else is spying for the Chinese, and it's often true. But soon enough they are setting me straight regarding what I have read--a process of re-education that will continue throughout this preliminary foray, and later, when I meet researchers in the field.

Unprecedented sandstorms erupted from China's Western regions recently and threatened to stifle Beijing. There was unprecedented flooding of the Yangtse. And unprecedented drought. And disappearing lakes. Consequently, the government is investing vast sums of money in environmental projects in those regions, one aspect of which is to "improve livestock production". International development agencies and the World Bank provide the ideology for these projects, which look convincing on paper because they use eco-speak to claim that traditional ways of using grasslands are detrimental to both profit and habitat. In other words, the nomads are responsible for the ecological destruction now causing such anxiety to the Chinese state.

The solution is to transform them into sedentary cattle farmers, such as we have here in Australia. To quote a government document, this will involve "changing the traditional and backward ideas of the pastoralists, and constructing a new pastoral region with the co-ordinated development of material civilisation, spiritual civilisation and ecological civilisation ..." In other words, agri-science, settlement and free enterprise.

The steppe, symbolic of a kind of wild, marauding freedom, which in all time has not been marked by a physical fence, is to be parcelled up into stock enclosures and paddocks, and planted with improved (introduced) grasses.

And all nomads are to be housed.

Unsurprisingly, the nomads themselves have not been consulted for this next great leap forward, despite an expertise gathered over generations, which has allowed them to make a living in surely the most difficult landscape on earth. Such knowledge is regarded as a hindrance to progress.

It is something of an idee fixe that nomads in marginal environments "overgraze" and therefore damage their pastures. Because they keep their stock numbers as high as possible at all times, it is assumed that grasses never fully regenerate. But contemporary research shows that high stock rates don't destroy pasture, as long as herds remain mobile. Nevertheless, the unsubstantiated assumption keeps re-circulating until it becomes received wisdom.

Tibetan nomads argue that the weather is so harsh, so unpredictable that even the best pastoralist can lose an entire herd in a winter storm, or a drought, or through some other random calamity. Increasing herd size during good years provides necessary insurance against such inevitable misfortunes. The strategy also makes for genetically strong animals; weak ones simply don't make it. Proof of the pudding is that this system has worked for millennia without damaging the pastures.

But when herds are kept in one place, nodes of over-grazing are inevitable. As the case studies coming out of Central Asia indicate, it is decreased access to traditional migration routes and increased no-go areas that cause soil compaction and advancing desertification.

Mobility is essential not just to the success of herding, but to social life as well. When animals are fenced in, the shepherds have little work to do. Women still have to keep a household functioning, still have to milk the animals, make cheese, and so on. But men with time on their hands gravitate to the towns to drink and play pool.

The new policy builds houses for the nomads and offers monetary incentives to abandon pastoralism. But the houses are often in newly constructed towns, completely off the rangelands. There are no jobs in these towns. Where there are jobs, in cultivation for example, these are usually contracted out to Han Chinese farmers from the east, or to locals who are better qualified.

When I asked A-den whether nomads could set up their own enterprises, he said: "To start up a business, you need good connections and money, and we who have lived as herders on the Chang Tang--where would we find either? I myself am illiterate. I have left the herds because I do not wish my children to suffer as I have. They must have an education. They must learn Chinese, and find good jobs. I am very lucky to have this job as a driver. It is because I can speak a little Chinese."

Wherever we drive that first day, modernity is constantly present in the form of a massive railway construction, connecting Lhasa with China. "You have to admit," I say, "that is an extraordinary engineering feat. And isn't it good that Tibetans can travel cheaply into China?"

Tenzing gives me a look and replies, "It will mean cheap travel for Chinese immigrants coming to take Tibetan jobs. And a cheap way for China to empty Tibet of its minerals."

We had intended to spend the first night in a monastery, but the road up to it is an impassable bog. A-den prevails upon a "rich" nomad lady to let us stay in her house. She is a fabulous-looking woman, carrying herself with confidence and poise. She is alone in the house, while her men are away shepherding in the summer pastures. Her fourteen-year-old daughter is herding female yaks, alone, up in the higher meadows.

The mother holds no concern for the girl at all. She takes for granted her ability and knowledge. They will be reunited in a couple of days.

The woman and her family would fit the statistic of "settled" nomads, but this is something of an illusion. The truth is that many "sedentary" families are still nomadic, only returning in winter to their houses. And even those who have settled permanently, and no longer own animals, refer to themselves, and indeed think of themselves, as nomads.

So far I've experienced no altitude problems, other than sudden attacks of narcolepsy. Like everyone else, I have had to shit outside, in the rain and hail. I am cold, wet, and I long for sleep. The rain pours down. Thunder roars and rattles around the mountains, lightning illuminates the monastery up above, stuck to its crag like a barnacle. The lady notices that I am in danger of falling face down into my boiled yak meat. She wraps me in a blanket, leads me to my cot and stokes the kitchen fire. I drift off while they murmur on, firelight flickering on her kitchen walls where large paper portraits of Deng and local communist officials gaze benevolently down upon us.

In the morning, she quietly enquires if I have a photo of the Dalai Lama with me and, if so, might she have it. Possessing such a photo can land you in jail.

Over the following days, I meet or camp with many families--some rich, some poor--but all of them proud of what they do. Whenever I comment on how tough their lives are, they laugh and assure me that it isn't so. Compared to farmers, their lives are easy. Nomads never have to dig, or carry heavy weights, or plant crops. Nomads let nature do the work. Farmers on the other hand have to struggle day in, day out. They never have a moment to relax. The nomads see their environment as generous and benevolent. Which isn't to say that they aren't interested in improving their living conditions with such modern innovations as mobile phones and motorcycles.

There is a surprising variety of responses to fencing. Some say they want it; others say it leads to all kinds of problems and conflict. I begin to sense that they see the parcelling out of land as inevitable, and they want to grab something while the going is good. Who knows what the government will do next? If you wait, or stick to the old ways, you might miss out on everything. Nomads are nothing if not opportunistic.

In any case, fences seem to be a fait accompli. They mark the end of Tibet's open space, and the transformation of a unique way of life.

The desire to control nomads politically and to incorporate them into non-nomadic cultures must have existed since the beginning of cities, when that schism between the settled and the mobile occurred. The city or state became the centre; beyond it was the outsider, the marauder, the barbarian. The colonial assumption that the "other" must be raised from dark bestiality into the light of civilisation began right there.

Han Chinese ethnocentrism--the belief that the more Chinese you are, the more civilised; and conversely, the further from Beijing you are, the more barbaric--is 2,000 years old. Communism didn't alter it much. According to that view the borderlands can be elevated by being incorporated into the body of the Motherland. It is this gradual Sinicisation that many in those borderlands fear.

One day, we pass through a small, ugly town in order to visit A-den's daughter. She is attending a college there, and learning to speak Chinese. Another of these gloomy, treeless towns on the outskirts of which is a cement barracks. She lives there, in a one-room cell. It contains a television set which is showing the usual Chinese soaps. I think to myself that there could be nothing more symbolic of the sedentary life than a cement room containing a television set and a sofa. Nevertheless, she is dressed as a nomad. And, like her father, she thinks of herself as a nomad. They can never go back to their life on the range. But the colonisers will have to work very hard indeed to assimilate such people.

Nomadism is the best strategy to employ in fragile and marginal ecosystems: it is a resilient, rational response to a variety of unpredictable circumstances. Yet governments the world over seem intent on destroying it. States have always felt uneasy about peripatetic peoples, who have little respect for borders, are difficult to control, evade taxes and tend towards independence of spirit. They are almost universally seen as unproductive members of society. But perhaps their greatest crime, in our times, is that they do not participate fully in the conspicuous consumption of unnecessary stuff. As a Mongolian proverb puts it:

Supreme treasure--knowledge

Middle treasure--children

Lowest treasure--material wealth

Towards the end of our time together, A-den, Tenzing and I make a visit to a high-altitude lake--one of those puddles of primordial sea left behind when two tectonic plates collided. We drive up to yet another pass and as we climb, the rain turns to sleet which turns to needles of horizontal snow. The road is a rutted track beside a partly frozen stream. How do people survive here in winter? What are they made of?

At the top of the pass a howling wind claws at millions of prayer flags distributing compassionate verses throughout the universe. Ten minutes later we are descending beneath the clouds into a different world.

White peaks inscribe an horizon of pure blue. Below us, the lake, turquoise, extends beyond the reach of sight. Green pasturelands, flecked with sheep and goats, stretch from the lake shore to the hills, and above that are the darker dots of grazing yak. Yak-wool tents are distributed throughout the flocks, like black spiders ready to pounce on the white specks around them.

Some cloud appears out of nowhere, scudding low and fast, dying the water petrol-green. A sudden squall. Tiny hail peppers our heads.

We make a dash for one of the tents, past the blue truck parked outside it, past the lines of milking goats, past the shepherd's motorbike.

The heavy tent flap is lifted and we are welcomed inside. A dung fire is crackling away, sending shafts of smoke up through a gap in the black wool roof. There are pieces of furniture and carpets. Warmth, comfort and courtesy. A shrine, photographs, devotional objects and butter lamps. The lady of the house is making cheese on a portagas stove. She plunges her red hands into almost boiling milk, again and again, until long scoops of gluey substance form, which are hung out to dry like stockings on a clothesline. It is delicious--a tough mozzarella. I am given a bed to stretch out on, and a prickly rug which smells of lanoline. Everyone gathers around to drink the inevitable butter tea, and talk and laugh. I ask if there might be a horse I could hire, in order to visit the lama living in a cave on the far shores of the lake.

A couple of days later, I am invited into his well-appointed cave, equipped with portagas, Tibetan furniture, library and hundreds of butter lamps, to which he constantly attends. A woman--his wife?--lives in the cave next door, and brings tea.

Afterwards I head "home" across the grasslands, following the shores of the lake, on a willing little pony who gallops at the touch of a heel. There are no fences from horizon to horizon.