There is a photocopied sign above the desk in the one-room office of the North St Elizabeth Cane Farmers’ Association that reads: “Plan ahead: it wasn’t raining when they built the ark!”

The association represents 564 smallholders growing sugar cane on the hilly margins of the Appleton rum estate in south-west Jamaica – and last week many of them were crowded into this office explaining exactly how their crisis-planning efforts were going.

The forebears of these men and women have been raising and cutting cane here for four centuries, back to slave days, and for nearly all of that time, the sentiment of that office motto would have looked absurd: for the small sugar producers of Jamaica, downpours of one kind or another have never stopped, and there has been precious little time for ark-building.

The last couple of years in “St Bess” have been an exception to that history. The farmers can talk of record production levels, good sugar yields and the first Fairtrade premium – a £39 per tonne bonus paid through a contract with Tate & Lyle – which they have invested in new truck-loading equipment as well as healthcare and education grants.

As ever, however, a flood of bad news is coming. Like most of the bad news this part of the world has ever received, this shift in fortunes has been made in Europe.

From the end of next year a change in EU policy will likely force these cane farmers and hundreds of thousands like them across Jamaica and beyond out of traditional work and into subsistence poverty.

The change is the end to the existing cap on European sugar beet production, which will flood a sugar market already, in anticipation, experiencing historic low prices.

The removal of the cap is part of a drive among finance ministers to curtail long-term arrangements assisting former European colonies in Africa, the Caribbean and the Pacific (ACP countries).

Under fierce lobbying pressure from multinational sugar processors – Coca-Cola, Nestlé, Mars – the EU argues that the reform is made in the spirit of freer markets and better value for the European shopper. (The market will remain, more free for some than others, however. Beet sugar grown intensively on rotation on European farms will, under the new arrangement, still be subsidised by every taxpayer on the continent at around £18 per tonne.)

In his office in Kingston, George Callaghan, chief executive of the Sugar Industry Authority in Jamaica, calls the change in EU policy an “earth-shattering event” for the island.

He predicts that the price farmers are receiving for cane (£390 per tonne) will be cut by 40% in 12 months, well below their break-even point.

“You have 165,000 persons directly and indirectly employed in cane,” he says. “The alternatives are very few. We have hurricanes here and every other type of crop is destroyed by a storm. Only cane survives.”

One irony is that as part of its sustainability agenda, the EU has since 2007 granted €142m (£105m) to the Jamaican government to privatise the sugar mills, improve productivity and pilot schemes to use cane for renewable energy.

“All the progress made will be lost overnight,” Callaghan says. The shockwaves will be felt far beyond Jamaica. Britain’s own Department for International Development (DfID) predicts that a perfect storm of the new EU beet policy and the current low sugar prices could force 6.4 million people into poverty by 2020 in ACP countries where cane is a staple crop.

I was travelling in the hills of Jamaica last week with a small team from Fairtrade to see at first hand how a few of those 6.4 million people plan to cope.

In the back of a minibus on the winding way up to the Worthy Park estate in the centre of the island, Michael Gidney, CEO of Fairtrade UK, explained the unique problems faced by the cane smallholders.

One is the fact that no European politician wants to talk about trade or humanitarian injustices around sugar. Because of associated health issues, it is the commodity without friends. “No brand wants to headline its presence in their product,” Gidney says. “Chocolate manufacturers will highlight Fairtrade cocoa, but never sugar.”

So this seismic change is passing under the political radar. “DfID’s job with our taxpayer’s pound is to lift people out of poverty,” says Gidney.

“A report has passed their desk saying that millions of people will be driven into poverty and they don’t say a word. In many cases, cane is everything for these farmers and their communities.”

You don’t have to travel far from the corrugated iron shacks that line the roads out of Kingston to understand the truth of that statement.

A sign at the entrance to the Worthy Park estate announces that it has been in continuous cane production since 1670. That production – and the (unmentioned) brutal West African slave trade that supported it – was the great cash machine of the British empire.

Towards the end of the 18th century, William Pitt the Younger estimated that four-fifths of British overseas income originated in the sugar trade. Jamaica was “a constant mine whence Britain draws prodigious riches”.

The grand Georgian squares of Bristol and London were built on the forced labour of plantations such as Worthy Park.

A couple of centuries later it was also, naturally, in these hills that the clamour for an independent Jamaica became insistent, with a general strike that began among sugar farmers and cane cutters. Jamaica’s two main political parties grew out of that movement.

The farmers remain at the sharp end of Jamaican history. The irony of their imminent catastrophe is that, in a community that has only ever known back-breaking work and precarious income, they have, these past couple of years, never had it so good.

Fitzroy Douglas, a bright-eyed 72-year-old, is chairman of the 1,500 Worthy Park cane farmers’ association smallholders and farms seven hectares. “When sugar is down, we go down with it,” he says, “when it comes up, we rise.”

The Worthy Park group was the first on the island to achieve Fairtrade certification. The contract with Tate & Lyle (which sells a Fairtrade-branded product in the UK) has given them an aggregated stipend this year of £375,000.

“It took a while to believe,” Douglas says, with a smile. “There were many stipulations, the phasing out of some dangerous chemicals and proper auditing. But we have got the right fertiliser and educated the 17 local groups here in best practice.”

They start to renegotiate their contract with Tate & Lyle, and begin to face the new reality, next month.

Alexia Ludford. Photograph: O'Brien Brown/Fairtrade Foundation

Further up into the hills, we watch some of that association-bought fertiliser (discounted because of bulk rates, and the currency certainty of the premium paid in US dollars) being distributed from the back of a container.

The farmers queue under an awning in the hot sun awaiting their allocation. They are kept in line – in every sense – by Alexia Ludford, the stepdaughter of Fitzroy Douglas and an eloquent advocate of the Fairtrade model.

A farmer herself, she says: “I do this work for free because I see how far the impacts have gone into the community. For the first time the farmers feel that they have a stake in future.”

It was Ludford who organised the shift from paraquat weedkiller to less toxic pesticides. She unearthed research, she says, that showed paraquat could cause impotence. Overnight she achieved what might have taken a government awareness campaign years.

Andrew Wright is Fairtrade’s Jamaican liaison manager. His father was a cane farmer. “Before he died he dragged me into it,” he says, with a laugh.

“He had 144 acres but I used to complain to him that he never made any money. He said: you do it; make a difference. So he would have been proud seeing some of this, I think.”

Wright is full of schemes and strategy papers to mitigate the challenges ahead. He doesn’t underestimate the crisis but he has faith that at least some of the changes – of empowerment, and adaptability – can be lasting.

While we talk he introduces me to Adolphus Ward, a cane farmer waiting for his fertiliser. Ward is 78. He has worked all his life in the same fields.

“I love the cane,” he says. “I tell you something: we need to step up production. We can pay cutters only 2,000 Jamaican dollars a day [about £12] during harvest. They have to find food and a place to live the year round.”

One of his lifelong problems has been getting his cut cane to the factory in the 72 hours before it spoils.

“All my life I have only one donkey and it is not enough,” he says. “Last year I applied for another donkey [from the Fairtrade premium]. I received two!” His best harvest saw him produce 39 tonnes of cane. This year he hopes for 50 tonnes. “I’m expanding,” he says.

There is a resilience about the farmers that they share with their crop. That rootedness in place could not be better illustrated than in a one-room village store in the parish of Trelawny in the north-west of the island, a couple of hours’ bumpy drive up from the all-inclusive resorts of Montego Bay but in another world entirely.

The store is run by Wellesley Bolt, lifetime cane farmer – he still owns some acres – and father of the fastest man who ever lived.

Last Saturday, like every day, Bolt was serving his few regular customers from behind his counter. In front of him was that morning’s paper which featured news of Usain’s ambition to retire in two years. Wellesley Bolt has no such plans. “I’ll die up here, no doubt,” he tells me, with a laugh.

When Bolt began raising his three children he was also farming cane, as his father had before him. In harvest season, his two sons might help in the fields before school.

“It is hard, rough work. I reaped 200 tonnes one year and I never got a dollar to cover the expense,” he recalls. “The juice was no good, they said.”

It was around then that Bolt decided to open his grocery store, which is stocked with a few baskets of yams and plantains and some household essentials. He talks with quiet amusement about how things have turned out.

He used to run at school, “but in those days we had no timing system so I don’t know how quick, but sure not as quick as my son”.

In another life, he suggests, without those extra hundredths of seconds, Usain might conceivably have gone into the farming, or followed him into the shop. As it is, his son’s fame has helped Bolt senior towards a new 4x4 and a small extension on the back of his house. Has he thought of moving away?

Wellesley Bolt outside his shop. Photograph: Nicola Frame/Fairtrade Foundation

Usain has tried to persuade him a few times. “But it doesn’t make sense for me to leave all the ground work here and start business somewhere else,” he says. “This is home.”

Also visiting Bolt’s shop is Paulette Richards, secretary of the Trelawny cane farmers’ association. She grew up carrying cane on her head over the river from her father’s farm.

She chats with Bolt about the two years from 2010 when the local sugar mill closed and the effect it had on people – a case study of what might come. Things fell apart.

“Sugar is the backbone of this place,” she says. “The whole parish was affected and it was like a ghost town. People planted short crops, peas, potato for themselves.”

Farmers took out loans, which they couldn’t pay; many moved away from the fields to she doesn’t know where. “You don’t have money for children in school. If I used to purchase three pounds of yellow yams now I could only purchase a pound. We are totally depending on the sugar.”

That dependence makes the coming shock more alarming. There are some seed projects exploring a shift to coffee or cocoa and to expand the potential for ethanol production from cane, but those markets take time and resources to access, neither of which the smallholders possess.

Jon Walker, the sugar manager for Fairtrade, has lately represented hope for the farmers. He is now in the uneasy position of counselling about alternatives in a bleaker future. How does that feel?

“It feels sad,” he says. “It feels unjust. It feels that we need to make it known that these communities are facing probably terminal decline, very soon.”

Where does he direct those efforts?

“The UK consumer has a big role,” he says. “They need to stick by businesses who stick by these people, who need the Fairtrade premium more than ever.”

And beyond that?

“Those in power have a responsibility to pay attention to people who don’t have votes for them.” Walker says. Currently, 25% of Jamaican sugar comes to Britain. It has been an enduring and one-sided trading relationship. “The problem is these farmers are out of sight and out of mind. And the worst thing is, they always have been.”

FAIRTRADE AND SUGAR

■ The global sugar export trade is worth $47bn.

■ Production is dominated by Brazil, India, the EU, China, Thailand and the US, which produce around 65% of the world’s sugar.

■ Sugar cane is a tall, bamboo-like grass that grows to a height of up to 6 metres (20ft) in mostly tropical countries. It is normally cut by hand and taken to sugar mills. Here the stems are crushed and ground and cane juice is extracted and used to make raw sugar.

■ Fairtrade focuses on sugar cane farmers in African, Caribbean and Pacific countries, including some of the world’s least developed countries.

■ There are just over 37,000 sugar farmers organised into 69 Fairtrade small producer organisations.

■ Half of the €7.4m in Fairtrade Premium funds that Fairtrade sugar farmers earned in 2011 was invested by the producers in business and organisational development or production and processing.

■ Most global sugar production is from sugar cane. About 20% of the world’s sugar comes from sugar beet, which is produced in temperate areas including the EU.

Source: Fairtrade International