When the vast expanse of rural Iowa was carved up for settlers in the 19th century, it was often divided into 160-acre lots. Four farms made a square mile, with a crisscross of dead-straight roads marking the boundaries like a sprawling chess board.

Within each square, generations of families tended pigs and cattle, grew oats and raised children, with the sons most likely to take over the farm. That is how Barb Kalbach saw the future when she left her family’s land to marry and begin farming with her new husband, Jim, 47 years ago.

“When we very first were married, we had cattle and calves,” she says. “We raised hogs from farrow to finish, and we had corn, beans, hay and oats. So did everyone around us.”

Half a century later, Kalbach surveys the destruction within the section of chessboard she shared with other farms near Dexter in southwestern Iowa. Barb and Jim are the last family still working the land, after their neighbours were picked off by waves of collapsing commodity prices and the rise of factory farming. With that came a vast transfer in wealth as farm profits funnelled into corporations or the diminishing number of families that own an increasing share of the land. Rural communities have been hollowed out.

And while the Kalbachs have hung on to their farm, they long ago abandoned livestock and mixed arable farming for the only thing they can make money at any more – growing corn and soya beans to sell to corporate buyers as feed for animals crammed by the thousands into the huge semi-automated sheds that now dominate farming, and the landscape, in large parts of Iowa.

Kalbach comes from five generations of farmers and suspects she may be the last. As she drives the roads around her farmhouse, she ticks off the disappearances.

Facebook Twitter Pinterest Barb Kalbach on the land she and her husband farm. Photograph: Scott Morgan/The Observer

“That’s the Shoesmiths’ place,” she said. “Two years ago, it had cattle, pigs and pasture.”

Now the land is rented out and is all given over to corn. A little further along, the Watts family’s farmhouse stands empty, its roof falling in. There are a few relics of the old farm at the place that used to be owned by the Williamses – an abandoned hen house and a bit of machinery – but the land is all corn and soya beans. The Denning house, on Walnut Avenue, was bulldozed after the land was sold and rolled into a bigger operation.

It’s a story replicated across America’s midwest, with the rapid expansion of farming methods at the heart of the row over US attempts to erode Britain’s food standards and lever open access to the UK market as part of a post-Brexit trade deal. Last weekend, the US ambassador to Britain, Woody Johnson, appealed to the UK to embrace US farming, arguing that those who warned against practices such as washing chicken in chlorine had been “deployed” to cast it “in the worst possible light”.

His message was greeted with anger by campaigners. Nick Dearden of Global Justice Now warned: “It is really an animal welfare issue here. If UK farmers want to compete against American imports, they will have to lower their standards or go out of business.” His words would come as no surprise to Rosemary Partridge, who farms in Sac County, western Iowa. She grew up on an Iowa family farm and then moved with her husband in the late 1970s to raise pigs and grow crops.

“In the past 20 years, where I am, independent hog farming just silently disappeared as the corporates came in,” says Partridge. “I live on a hilltop. I can see seven farm families, people my kids went to school with. They’re all gone now. My county has 11 small towns, and it’s almost like I could look back in slow motion and just see the businesses change and disappear. We’ve become poorer. Our communities are basically shattered and in more than just an economic way – in a social way too.”

Facebook Twitter Pinterest Across the state, farmhouses where generations grew up lie abandoned. Photograph: Scott Morgan/The Observer

This collapse has in good part been driven by the rise of concentrated animal feeding operations, or Cafos. In these industrial farming units, pigs, cows and chickens are crammed by the thousand into rows of barns. Many units are semi-automated, with feeding run by computer and the animals watched by video, with periodic visits by workers who drive between several operations.

“That’s how I end up with 40,000 hogs around me,” says Partridge.

Cafos account for only a small proportion of America’s 2 million farms, but they dominate animal production and have an outsize influence on crop growing, particularly in the midwest.

By one calculation, the US has around 250,000 factory farms of one kind or another. They have their roots in the 1930s, with the mechanisation of pig slaughterhouses. By the 1950s, chickens were routinely packed into huge sheds, in appalling conditions.

In the early 1970s, US agriculture secretary Earl Butz pushed the idea of large-scale farming with the mantra “get big or get out”. He wanted to see farmers embrace what he regarded as a more efficient strategy of growing commodity crops, such as corn and soya beans. Some farmers invested heavily in buying land and new machinery to increase production – taking on large amounts of debt to do so.

A decade later, the farm crisis hit as overproduction, the US grain embargo against the Soviet Union and high interest rates dramatically drove up costs and debt for family farms. Land prices collapsed and foreclosures escalated.“Every blow to independent farming made it more of an opportunity for large corporations to come in,” said Partridge.

In 1990, small and medium-sized farms accounted for nearly half of all agricultural production in the US. Now it is less than a quarter.

As the medium-sized family farms retreated, the businesses they helped support disappeared. Local seed and equipment suppliers shut up shop because corporations went straight to wholesalers or manufacturers. Demand for local vets collapsed. As those businesses packed up and left, communities shrank. Shops, restaurants and doctors’ surgeries closed. People found they had to drive for an hour or more for medical treatment. Towns and counties began to share ambulances.

Facebook Twitter Pinterest Rural Iowa communities such as Williams are seeing business and services close down. Photograph: Scott Morgan/The Observer

Corporate agriculture evolved to take control of the entire production line from “farm to fork”, from the genetics of breeding to wholesalers in the US or far east. As factory farms spread, their demands dictated the workings of slaughterhouses. Smaller abattoirs, which offered choice and competitive prices to family farmers, disappeared, to be replaced by huge operations that were further away and imposed lower prices on small-scale breeders such as the Kalbachs.

“By the time you paid to transport them the extra distance, and they were paying you less than they paid the corporations because you weren’t bringing the big numbers, there was really no money in it,” says Kalbach.

The buying power of the Cafos also helps drive farmers’ decisions on which crops to grow. With no livestock, the Kalbachs were forced into gowing corn and soya beans to sell to factory farms as animal feed or to corporations for ethanol.

Iowa is not alone. Missouri, to the south, had 23,000 independent pig farmers in 1985. Today it has just over 2,000. The number of independent cattle farms has fallen by 40% over the same period.

Tim Gibbons of Missouri Rural Crisis Center, a support group for family farmers set up during the 1980s farm crisis, says the cycle of economic shocks has blended with government policies to create a “monopolisation of the livestock industry, where a few multinational corporations control a vast majority of the livestock”.

Gibbons explains: “They are vertically integrated, from animal genetics to grocery store. What they charge isn’t based upon what it costs to produce, and it’s not based on supply and demand, because they know what they need to make a profit. What they have done, through government support and taxpayer support, is to intentionally overproduce so that the price stays low, sometimes below the cost of production. That kicks their competition out of the market. Then they become the only player in town.

“Over time, it has extracted wealth and power from communities. We can see how that has impacted rural main streets. You can see the boarded-up storefronts. You can see the lack of economic opportunity.”

Gibbons says that corporations game the system by obtaining low-interest, federally guaranteed loans to build Cafos that then overproduce. But they know the government will buy up the surplus to stabilise prices.

Facebook Twitter Pinterest Activist Nick Schutt in Williams, Iowa. Photograph: Scott Morgan/The Observer

“The system has been set up for the benefit of the factory farm corporations and their shareholders at the expense of family farmers, the real people, our environment, our food system,” he adds.

“The thing that is really pervasive about it is that they control the rules of the game because they control the democratic process. It’s a blueprint. We’re paying for our own demise.

“It would be a different argument if it was just based upon inevitability or based on competition. But it’s not based upon competition: it’s based upon squelching competition.”

There are about 70 million pigs in the US at any time, most of them destined for the dinner plate. But one in 10 are breeding sows, and the majority of those are in Cafos. The biggest pig farmer in the country is Virginia-based Smithfield Foods, which has nearly a million sows in the US (and more in Mexico and eastern Europe). Iowa Select Farms has one of the fastest-growing Cafo operations in the country, with 800 farms spread through half of the counties in Iowa.

Yet few of the economic benefits spill down to the communities around them. Workers are often poorly paid; many are bussed in. That they often include immigrants has sharpened the criticism from men like Nick Schutt, who used to work at Iowa Select, driving pigs in livestock trucks and handling sows. He says he earned $23,000 a year for 12-hour days and no overtime.

“These companies claim they’re creating all these jobs, but who’s coming? Not people with families who create communities.”

Schutt lives in Williams, a small town in central Iowa, which is surrounded by Cafos and currently fighting to keep a big new one out, saying factory farms pollute the environment and depress property values. When the wind blows in the wrong direction, the stench from huge lakes of pig manure wafts across the town.

The high school Nick Schutt attended has closed. His daughter was in the last class to graduate. As Williams declined, the only doctor shut his clinic and left town. Schutt’s mother used to own a restaurant: that closed along with the town’s three grocery stores.

In Blairsburg, seven miles away, pretty much every shop except the post office is gone. The neighbouring hamlet of Wilke now consists of three animal sheds on land where dwellings were bulldozed from existence. Two-thirds of the counties in Iowa, almost all of them rural, have seen their populations decline since 2010, according to the US census.

North of Williams is a Cafo whose name, Quality Egg, has come to represent the worst of factory farming. In 1988, New York temporarily banned the sale of its eggs after salmonella killed 11 people. In 2017, its former owner, Jack DeCoster, went to prison, along with his son Peter, over a 2010 salmonella outbreak that made tens of thousands sick, left some with permanent injuries and prompted the recall of more than half a billion eggs shipped from Iowa factory farms. Quality Egg pleaded guilty to selling eggs with false expiry dates and to bribing an agriculture department inspector to approve the sale.

Facebook Twitter Pinterest Farmer Jon Shelley moves bales of hay to feed cows in front of an abandoned school house. Photograph: Scott Morgan/The Observer

DeCoster had a long history of paying fines worth millions of dollars for animal cruelty, falsifying records, swindling contractors and polluting – without much impact on the way he did business. He was found to have made immigrant workers, many of them in the US illegally, live and work in squalid and unsafe conditions. The company paid $1.5m to settle allegations that supervisors at Iowa plants raped female workers.

DeCoster is an extreme case, but around Iowa he’s seen as emblematic of how the industry uses its money and influence to impose its will, including changing planning and environmental regulations.

Much of this is the result of agricultural corporations pouring millions into lobbying state governments. But Gibbons says Washington also bears some responsibility. He accuses President Barack Obama’s administration of failing to deliver on promised reforms that would have benefited smaller farmers. It is this, he says, that damaged Obama’s standing among farmers and drove up their support for Donald Trump.

Barb Kalbach is not optimistic about the future. Her son will not be taking over the farm. She hopes the land will stay in the family for at least another generation, but expects it to be rented out and subsumed into some larger operation.

But Kalbach fears something bigger than the loss of her own farm. Farmers are ageing and their children either have little interest in working the land or cannot afford the sophisticated equipment needed to compete with corporations.

“Investors buy the land, and they have tractors and combines that you can run by computer,” she said. “They’ll hire somebody to sit in a little office somewhere and run that stuff off the computer and farm the land that way. Now what you’ve done is you have lost the innate knowledge of how to grow food and raise animals. You’ve lost a whole generation of it, probably two. Now we are going to rely on a few corporations to decide who is going to eat and who isn’t. We’re one generation away from that picture right now.”

In Williams, Schutt says he’s seeing a community of owners becoming workers: “It’s going to be like Russia with serfs. If you want to work on a farm, you’ll have to work for them. We’ll give you a job, but you’re going to be working on our terms. We control everything. Small farms can’t survive.”

Kalbach agrees. “I think they’re done,” she said.