Genetic uniformity is at the heart of modern agriculture. This makes us vulnerable to plant diseases.
No one really knows how the Bipolar is may this fungus got into U.S. corn fields.
But in the summer of 1970, it took its revenge, inflicting a disease called southern corn leaf blight, which causes stalks to wilt and die.
The South was hit first, then the disease spread through Tennessee and Kentucky before heading to Illinois, Missouri, and Iowa – the heart of the Corn Belt.
The destruction was unprecedented.
In total, the 1970 corn crop was reduced by about 15 percent.
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Collectively, farmers lost nearly 700 million bushels of corn that could have fed livestock and humans, at an economic cost of $1 billion.
More calories were lost than during the Great Irish Famine of the 1840s, when disease decimated potato fields.
In fact, the southern corn leaf blight problem began years before the 1970 outbreak, when scientists in the 1930s developed a variety of corn with a genetic trait that allowed companies to seed companies to get started easily.
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Farmers appreciated the high yields of this variety.
By the 1970s, this particular variety formed the genetic basis for up to 90 percent of the corn grown in the country, compared to the thousands of varieties' farmers had previously grown.
This particular strain of corn, known as cms-T, has been found to be very susceptible to southern corn leaf blight.
So when an unusually warm and humid spring favored the fungus, it had a glut of corn plants to burn.
At the time, scientists hoped a lesson had been learned.
“Never again should a major crop species be fashioned into such uniformity as to be so universally vulnerable to attack by a pathogen,” wrote plant pathologist Arnold John Ullstrup in a study on the subject published in 1972.
And yet today, genetic uniformity is one of the main characteristics of most large-scale agricultural systems, leading some scientists to warn that conditions are ripe for larger outbreaks of plant diseases.
“I think we have all the conditions for a pandemic to occur in agricultural systems,” said agronomist Miguel Altieri, professor emeritus at the University of California, Berkeley.
Hunger and economic hardship would likely follow.
Climate change adds to the danger: Changing weather patterns are poised to upend the distribution of pathogens and bring them into contact with new plant species, which could worsen crop diseases, said Brajesh Singh, soil science expert at Western Sydney University. In Australia.
Integrating biodiversity into agriculture on a large scale could bring agriculture out of this crisis.
Here and there, some farmers are taking steps in this direction.
But will their efforts catch on – and what will happen if they don’t?
Farms cover nearly 40% of the planet's land, according to a 2019 report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.
Nearly 50 percent of these systems consist of just four crops: wheat, corn, rice, and soybeans.
Diseases are commonplace: globally, $30 billion worth of food is lost to pathogens each year.
Things weren't always like this. In the United States, for example, at the dawn of the 1900s, food was produced by humans, not machines: more than 40 percent of the American workforce was employed on a multitude of small farms growing a wide range of crop varieties.
The British Empire sparked the transition to today's industrialized food system, said historian Lizzie Collingham, who wrote the book Taste of War: World War II and the Battle for Food.
By the early 1900s, the British Empire had learned that it could “essentially treat the entire planet as a resource for its population,” Collingham said.
For example, she bought cocoa from West Africa, meat from Argentina and sugar from the Caribbean. Suddenly, food is no longer something you can buy from the local farmer, but a global product subject to economies of scale.
Intercropping means growing two or more crops in the same field, alternating rows or mixing crops in the same rows.
It is a modern reinvention of centuries-old techniques like those used by Altieri, and a way to introduce biodiversity into large-scale agriculture.
In Muck's case, he sows wheat with soybeans.
Wheat seeds are buried in October, and by February the plants are growing in the ground.
Then in April, he adds soybeans between the rows.
The two crops grow together until harvest, around July 1.
Unlike the wheat that Muck grows as a monoculture, he doesn't spray fungicides on the intercropped wheat at all – they simply don't need help to stay healthy.
The crop combination likely promotes air flow that dries out moisture and prevents fungus growth, Mauck said.
As climate change brings more extreme storms to the region, he welcomes the help.
Mauck's experiences are far from unique. When biologist Mark Boudreau of Penn State Brandywine reviewed 206 intercropping studies involving a wide variety of plants and pathogens, he found that diseases were reduced in 73 percent of the studies.
In China, farmers have been experimenting with intercropping for decades, and the method is gaining ground in Europe and the Middle East, Boudreau said.
But in the American Midwest, Mauck said intercropping makes it “a little weird.” He speaks at around twenty conferences each year to raise awareness of this subject and other sustainable agricultural practices, and he also has a large following on social media.
He has convinced some of his fellow farmers to try intercropping, but progress has been slow.
Lack of equipment is a big part of the problem, said Clair Keene,
a North Dakota State University extension agronomist.
Infectious Diseases Plants and Global Crop Yields
Farm equipment manufacturers have not invented the machine that allows farmers to harvest mixed crops separately, and farmers generally do not have time to harvest multiple crops.
It would be a fairly easy problem for farm equipment companies to solve, Boudreau thinks, if farmers put a little pressure on them.
In North Dakota, the humble chickpea just might provide the motivation farmers and farm equipment companies need.
In recent years, the profit margin on chickpeas has been two to three times that of spring wheat, a common crop in the region.
But there's a problem: Chickpeas are very susceptible to a disease called Ascochyta leaf blight.
“It can just wipe out the field. For example, there will be no more chickpeas to harvest,” Keene said.
To avoid this fate, farmers spray their chickpeas with fungicides between two and five times a year, and the cost of fungicides significantly reduces the profit margin.
Intercropping could be an affordable alternative.
Keene and others have found that Ascochyta leaf blight decreases by at least 50 percent when chickpeas are grown with flax.
Like Mauck's fields, Keene believes the flax promotes air circulation around the chickpeas, reducing humidity and preventing the growth of the blight-causing fungus.
When Keene looks at the vast fields of crops that characterize her home state of North Dakota, she sees two sides of modern agriculture.
On the one hand, monocultures have provided many people with a vital source of calories.
“As Americans, we use our landscape to provide a quality of life that, at least on the whole, generations before us never dreamed of,” she said.
And who is behind this? Farmers. We owe them a lot. »
But the same agricultural system has had a tremendous impact on the landscape, from the native plants that once thrived on Midwestern prairies to the microbes that inhabit the soil.
Changes are brewing in Earth's climate, and a system we rely on may begin to falter.
Modern agriculture has provided comfort to humans: “But,” Keene asked, “at what ecological cost?”