On the bus out of Rio Branco, along a dusty road south and headed to the rainforest town of Xapuri, it becomes clearer than ever that this group of British kids are...well, something else. For a start, they are anti-green. And dogmatic with it.

We are off to meet some rubber tappers in the heart of the state of Acre, in western Amazonia. This is Chico Mendes country. We are, in other words, to meet the men and women whose plight is supposed to epitomise the destruction of Brazil's rainforest. Alongside the dead straight road, just the kind Chico Mendes died protesting against, there are the cattle ranches whose expansion he most dreaded. He became a hero and martyr, the green equivalent of a Che Guevara. That was twelve years ago this December. About the time of Mendes's death John Conroy, now 32 and a Latin American studies graduate, and the best informed man on our bus, was a conventional enough green. Perhaps he was a bit fiercer than most, because he's a fierce sort of man.

Conroy wandered in these parts for six months, living with rubber tappers. The result was a damascene conversion on the dirt road to Xapuri. He learned that the local forest-dwellers wanted and needed to be able to farm more of the rainforest around them. "They want the things everybody wants", he says. That's TVs, cars, education, travel - the works. "Don't forget, these are people whose grandparents and parents were dumped here to tap rubber during a boom, and were left here when the boom collapsed. They have no reason to love the rainforest particularly". He agrees with the view that Mendes was a union man, not a green, and that it's the difficulty of getting secure tenure to decent tracts of land, and the new purism about the forest, which hold the trappers in poverty.

This argument has it that there's a circularity here. The forest dwellers are celebrated by the greens only because they guarantee the existence of the forest, but the greens also insist, wrongly, that the forest can't stand the sort of limited development a respectable life for its inhabitants demands.

A meeting is held. There are 20-odd of us on the air conditioned bus, and Ceri Dingle - rounded, 40-something, the daughter of a Dorset dairy farmer, and the boss of WORLDwrite, which has organised this extraordinary tour - galvanises her troops. "I want you to split into groups and discuss an agreed area of what we're here to see. In ten minutes, you'll report back to the whole group". Yes miss.

Some of the feistiest and most motivated sixth formers, gap-year students, and university undergraduates and graduates you're ever likely to meet, do as they are bid. But the agenda is Conroy's, and the discussion is about the follies of NGOs [Non Governmental Organisations] and the arrogance of far away affluent people prescribing rules for the future of Amazonia from the comfort of offices paid for by gullible western greens. Some of these young people, who meet most weeks in WORLDwrite's London HQ, have read quite widely and all have studied in detail an information pack which puts the cases for and against the green approach to Amazonia. Simply by putting a pro-development case alongside the other, this is a unique document.

Every now and again the bus careens across the empty road to avoid giant ruts. Out of the windows, there is an wide vista of green grass, looking only a little parched, in which the occasional tree stands rather forlornly as a reminder of the rainforest which was here ten or twenty years ago. The grassland stretches back several miles both sides of the road, with the forest lurking as a horizon, where civilisation's maw abruptly ceases. The ranch houses look solid and even luxurious. The cattle are rangy but strong-looking. It is a scene which belies the idea that ranching can only survive for a year or two in ex-rainforest. It's certainly a reminder that Amazonia is all sorts of places, and that Acre has some of the most fertile.

I've been assigned to a group which is discussing the idea of "sustainable development", and find myself defending the concept against young people who have been told that it's an idea which is locking poor rural people into poverty because the greens have run away with it. Hang on, I say: it's a bit of an oxymoron, but at least it invites economists to consider whether development is doing unacceptable damage, and it reminds greens that a bit of damage may be acceptable if it advances people's lot.

In Xapuri, we see the house where Chico Mendes was murdered and, by the river, our first rubber tapper. He is carting resin blocks about the size of small paving stones. As he heaves up the steep bank and dumps his shoulder's load of ecological harvest into a tractor provided by his co-operative, we discover that he's paid about enough for a cheap lunch for a day's work gathering. We are told by locals that even that pay arises only because a tyre company has a special deal in place to encourage such green approaches. Elsewhere, the market has collapsed.

Besides, as an Indian chief had told us back in Rio Branco, it can take a month to get any produce at all out of the jungle. "We need roads", he said. "Now we can only reach one market, and not always that. We need to reach at least two markets". This man, who had obviously grasped the essence of the cash economy, said he had recently been sent away to Sao Paulo to learn about ethnicity. It was hard to resist the feeling that this was part of the politically correct agenda whose underlying purpose may be as much to head local people's minds away from the dream of western development as it is to enlighten indians.

We met the chief whilst he was on a language course. A month's travelling to and fro, and a couple of months learning Portugese well enough to teach it properly to his followers: "We want our own language preserved," he said. But he said many Indians preferred to use Portugese, partly to get a better deal at market, and partly because only in the European language could they speak to neighbouring tribes, each with its own language. It's an argument in favour of a lingua franca which is as old as the imperialism of Rome and Britain. It's also a death knell to the diversity of cultures so beloved of many foreign anthropologists.

Pedro Teles, a rubber tapper and teacher, talked to the group about wanting tractors and fertilisers, and more farmland. His wife was on the solar-powered radio to town as he spoke; his kids were listening to funky sambas on a ghetto-blaster; granny was down the road smoking ready-mades with her son's farm-workers.

He remarked how much he enjoyed taking the family on trips to the outside world. Barely surprising that he endorsed the view of the greenest of local politicians, the Worker's Party senator, Marina Silva: that better transport is vital to people in Amazonia.

Had Chico Mendes lived, he might well have come to accept this view. But he might also be spouting the other half of this message, which the WORLDwrite crew loathed. One afternoon we sat as 12 NGO leaders spouted anti-capitalist, anti-development messages which could have come straight from the UK Green Party. Helen Sewell, one of the youngsters, recalled the meeting: "One NGO woman said that western ideals and western material goods should not be imposed on the indigenous people, but she might as well have been saying western ideas and western goods should not pollute their minds. But the indigenous people know what they want, they're not stupid".

That night, a smaller group listened to Antonio Alves, a journalist and influential green theorist, as he described a curious blend of self-sufficiency and eco-friendly farming and trading. "That's fine", fumed John Conroy. "But they must know there's no real market for this stuff."

It's a thousand kilometres due east from Rio Branco to Manaus. I made the flight in daylight, and most of it across cloudless skies. Five minutes out of Rio Branco, the farmland and the ranching stopped. An unceasing carpet of tractless rainforest - wasteland, one would once have said - stretched for the duration of the journey. This is the state of Amazonas, three times the size of France, with two million mostly urban inhabitants. "We still have 97 per cent of our rainforest", Vicente Nogueira, the state's American-educated head of environmental protection, told the youngsters. He went on to describe the new conviction that very little development should be allowed in the rainforest. But you could be encouraging controlled forestry, the group insisted. "It's like assets in the bank for us", he countered. "We know it's there and one day we may need it". Manaus looks out on hundreds of miles of rainforest in pretty well any direction, and it does so partly because it is a free trade zone. The message was that industry in the right places could help keep the rainforest intact. Besides, Dr Nogueira said, Amazonas' rainforest was less amenable to conversion than Acre's.

"You know, not all indians want economic development", he told the restive group. The city last year invited one proudly traditional group to contribute to Brazil's Indian Day by sending some young people to see the city. "We wanted boys and girls, but they said no, and no it was. They sent only boys."

At the National Institute for Amazonian Research (INPA), also in Manaus, the young people pressed to be told how the rural Amazonians (perhaps 5 million, or a quarter of the total) could be supposed to get the development many of them manifestly wanted. Joa[[[watch accent]]o Ferraz, an INPA ecologist, told them it wasn't just a question of not wanting to allow forest-dwellers more forest land to use. "The challenge we face is that the most sustainable uses of the forest are very small scale, and no-one has the recipe for bigger scale operations". He said lack of capital and markets, corruption, and ignorance all compounded ecological fragility in making development difficult in the hinterland.

The dilemma the officials face is tangible. After years of being castigated for allowing and encouraging all sorts of inappropriate conversion of parts of the forest, the world's aid agencies and the Brazilian government have accepted much of the green rhetoric. The eco-message may go too far, but it's the only message the West will fund in the rainforest, over which satellites are now unsleeping policemen, and in which many areas aren't suitable for much more than tree-growing anyway. And suddenly, out of the blue, there comes a party of young people with a "people first" agenda.

Many of the young were robust to the point of rudeness in their inquiries, though there was much more diversity of opinion amongst them than was at first obvious. But even if the WORLDwrite crew are agenda-laden, the genius of their enterprise was to take their ideas and questions the length and breadth of Brazil, and from top to bottom of Brazil's society. It will take people like WORLDwrite's opinionated adventurers to embarrass the world out of its comfortable, tree-hugging certainties.