The so-called “lungs of the world” are belching smoke as farmers set out after 10 August in a “day of fires” to clear forest for grazing cattle and planting soybeans. The result was more than 10,000 new fires spreading in the Brazilian rainforest, kindled by drought that drives wildfires raging from Russia to Africa.

Brazilian deforestation is no act of non-government organizations, as the president, Jair Bolsonaro – who called himself “Captain Chainsaw” – absurdly claimed. He ran for president last year exhorting homesteaders to stake their claim by cutting or burning. They scoff at scientists and outsiders alarmed that the planet could cook that much faster if the rain forest is torched, and have openly stated their goals shielded in sovereignty.

The number of fires increased more than 80% this year as the US trade war with China peaked. The Day of Fires was called just as China declared it would no longer buy US agricultural products. The biggest import from China was soybeans, accounting for over half Iowa’s annual crop.

This is part of a long-term development that has seen China invest in production capacity in Central and South America to shift its soy dependence away from the US.

Brazil is now the top exporter of soybeans to China. It is also building its beef export business in Asia as an African virus cut the Chinese hog herd in half, which will take years to rebuild.

As Brazilian savannas that grazed livestock give way to soybean cultivation, cattle move into the rain forest along with row-crop production.

As if the world were not already awash in soybeans, and corn. Upper midwest farmers have watched their soy prices drop by a third as Donald Trump and the Chinese president, Xi Jinping, ratchet up their rhetoric and tariffs.

Iowa soybean growers carefully cultivated China for decades to open up new export markets. Since the days that Nixon’s agriculture secretary, Earl Butz, commanded farmers to plant fencerow to fencerow to feed the world, China became Iowa’s top soy customer. When the state’s governor, Terry Branstad, was appointed ambassador, Iowa farmers thought the key to the door of the Forbidden City had been given to them. Then Trump, who said he loves farmers, started the trade wars with China, Mexico and Canada.

“You will never see the Chinese market the way you had it,” former Mexican ambassador to China Jorge Guajardo told me. “They will never make the mistake of depending on the United States again.”

He adds that Mexican buyers also are leery of counting on US agriculture suppliers. They have a free trade agreement with Brazil. They do not have one with the US.

Arrangements have been made. The supply chain has been twisted another direction. Now, Brazilians are using that language of feeding the world, and planting every last acre by expropriating rain forest from indigenous people if Chinese demand dictates it. And it does.

The soybeans sit in the bin in Iowa and Illinois awaiting a better day, as a harvest fast approaches, while the rain forest burns. In the rolling hills of southern Iowa painted in green pasture you can’t scare up a cattle buyer anymore. The beef slaughter plants in Fort Dodge and Denison are closed now, as the action moves to South America’s new frontier. We are growing so much soy and corn that the Gulf of Mexico is choking from excess fertilizer streaming down the Mississippi River. What we can’t feed to hogs and poultry we burn for ethanol, competing with the Brazilian cane growers who create environmental disasters all their own. Because of the trade wars, Trump has doled out $30bn over two years in disaster payments to make up for depressed soybean markets. We can’t seem to give it away. It has many Iowa farmers talking with presidential candidates about doing things differently – like growing less corn and beans, and instead fighting the climate crisisby planting crops that capture carbon while restoring soil.

Yet the forest burns, and its carbon-capturing capacity goes up in smoke. All for some cheaper soybeans and hamburger. Trade wars may end, but supply chains are hard to bend back.