The secret to curbing farm emissions is buried in the Stone Age

The secret to curbing farm emissions is buried in the Stone Age

2020-04-01 08:00:20

Reduced tilling, cover crops, and more trees can pull more carbon from the air and into the ground. (Patrick Leger/)

Along a stretch of rural highway in the coastal plains of North Carolina sits an unusual forest. The viridian-green branches of loblolly pines rise 60 feet above a carpet of soft, tufted grasses, rippling slightly in the breeze. The trees are widely spaced, 20 to 30 feet apart, with their lower limbs removed, creating an airy, cathedral-like canopy speckled with sunlight filtering through the needles.

The woodland has a strangely serene, primeval feel. A sudden wave of grunting reveals large black shapes moving in the distance. A pickup approaches, further breaking the reverie, and out hops a slender middle-aged man in a ball cap.

“Buron Lanier,” he says, extending a hand. “Sorry I’m late. I was just finishing up with a calf.”

The shapes, Lanier’s Red Angus cattle, amble over. This forest, 100 acres of his 400-acre Piney Woods Farm, is their grazing ground—a modern incarnation of an ancient technique called silvopasture, an integration of forest and fauna.

To Lanier—a third-generation grower whose ancestors raised tobacco where his pines now stand—the unusual scheme, which he’s cultivated over the past 30-plus years, is common sense. The trees boost his bottom line through periodic timber sales, and cattle fatten up 20 days quicker when not forced to munch on sudangrass in 90-degree heat.

He waxes eloquently about the wildlife habitat, erosion control, and sense of calm this land provides. “I love the pristineness, the peacefulness of the trees,” he says in a soothing drawl as he drives through his ranch as if on a Jurassic Park agriculture safari. He points out the calf he midwifed earlier, wet and wobbly in a sweetly scented glade. “Who wouldn’t want to give birth in a nice shady bed of grass?”

Minus the pickup truck and some electric fencing, it’s a scene one might have encountered in the Neolithic period, when humans first domesticated cows from the aurochs roaming the Fertile Crescent. The practice was among the earliest agricultural endeavors, but the bare fields and feedlots of modern farms and ranches have largely swept it away.

Environmental scientists, though, see the reemergence of silvopasture as a means to slow down climate change. Livestock produce two-thirds of all agricultural emissions, and methane from burping cows is the largest slice of that. Lanier is skeptical that global warming is real, but his pines, in siphoning CO2 from sky to earth, are nonetheless helping cancel out his bovine contribution to planetary disaster.

Farmers and ranchers across the country are turning back the agricultural clock in order to convert the land they steward into ammunition in the climate fight. In total, cultivation sends about 8 billion tons of carbon into the air each year. That’s nearly one-quarter of emissions—​roughly the same as heat and electricity production combined, and far more than transportation.

Anecdotally, the United States Department of Agriculture sees a tiny but growing number of silvopasture farms, while other methods that suck greenhouse gases from the air—​collectively known as carbon farming—​are experiencing greater resurgences. The once-ubiquitous practice of plowing, which chucks soil-bound carbon into the atmosphere as it churns the ground, has disappeared from 21 percent of acreage. Cover crops, typically sown in the offseason and left in fields to decompose, are also rising in popularity.

Such practices have been on the upswing since the 1990s, even among the large-scale operations that supply the likes of General Mills and McDonald’s. But for the cash-strapped midsize farmers who represent the bulk of American growers, adoption can be a challenge. While these methods can slash costs (less tillage means less tractor fuel, and richer soil requires fewer fertilizers), they can also risk yields. Agronomists are working on a road map to help folks invest in changes—and to elevate climate-conscious practices to a place where we can feed the world’s 7.5 billion people.

Finding those answers is vital for the planet. According to analysis from Rattan Lal, director of Ohio State University’s Carbon Management and Sequestration Center, farm-​based emissions trapping could get us most, if not all, of the way to the goals of the Paris Agreement. “This is if somebody at the United Nations turns a switch and says, ‘Thou shalt do everything perfectly,’” he says. “Even if we can achieve half, or a third, of what’s possible under optimal conditions, we will have made a difference.”

Combining grazing grounds with cultivated forests can help cancel out the methane from cow burps.

Combining grazing grounds with cultivated forests can help cancel out the methane from cow burps. (Patrick Leger/)

At Cherry Farm, a 2,200-acre facility affiliated with the University of North Carolina, not far from Lanier’s ranch, biologist Tomás Moreno weaves down narrow aisles of organically raised cornstalks and stops at an airtight metal chamber resting atop the soil. Slipping a syringe through a rubber gasket in the lid, he draws air that’s percolated up from the ground. This sample is bound for a USDA lab that will analyze its greenhouse-gas content.

As part of a long-term project kicked off in 2018, Moreno and his colleagues repeat this process throughout the year on plots representing more than a dozen cultivation regimes. “We still have more questions than answers,” Moreno says, as he shoos a giant black-and-yellow spider. Many of the methods they track—including varying levels of tillage, cover crops, and livestock integration—are modern-day analogs of Neolithic agricultural life. What they find will help determine how best to replenish the carbon the ground has lost.

Land naturally wants to hang on to carbon. Vegetation (the more, the better) inhales the element from the sky. Roots excrete some of it into the soil, feeding underground microbes, which poop and die and aggregate with decomposing flora and fauna to form humus, a dark, crumbly substance that is 50 to 60 percent carbon. A sponge for nutrients and moisture, the material can remain stable in the soil for millennia.

Early farming scarcely disturbed this cycle. Chickens tamed by Southeast Asian hunter-gatherers some 10,000 years ago foraged in forests rich with early crops like bananas and mangoes. Similarly, the Amazon was once a loosely kept garden of more than a hundred species, including cacao and pineapple. Parts of the rainforest still hold terra preta—​“dark soil” in Portuguese—​a nutrient-​filled groundcover.

As societies grew and needed to scale up agricultural production, carbon-rich landscapes became carbon-impoverished. Farmers set fire to larger and larger tracts, the easiest path to clear the ground—​but also a huge polluter, and a gateway to the second climate culprit, the plow.

Some 7,000 years ago, Mesopotamians developed the ard, a wooden hoe-like implement pulled behind draft animals to stir the earth in barley and chickpea fields. Sometime around year zero, it evolved into an iron tool. When John Deere introduced its ubiquitous tractors in 1918, the practice entered an exponential growth curve.

The glinting steel of a plow blade holds obvious allure. Digging uproots weeds that hog nutrients, water, and sun, and it loosens the ground so tender seedlings can easily grow. But exposing soil lets carbon compounds oxidize into the atmosphere, where they can no longer do what they’re meant to: feed plants. The plow cuts like a double-edged sword—​increasing yields but cementing reliance on fertilizer.

Thanks to these methods, we’ve released up to 600 gigatons of carbon—about 30 percent of what humanity’s flung into the atmosphere—since we began farming. Soil scientist Lal estimates that it’s possible to recapture 4 to 5 gigatons per year through better land management.

Undisturbed topsoil holds onto more carbon and nutrients than ground churned up by heavy plowing.

Undisturbed topsoil holds onto more carbon and nutrients than ground churned up by heavy plowing. (Patrick Leger/)

Today, ditching tillage seems unfathomable, but ecosystems have long managed to produce robust growth without it. In his 1943 book, Plowman’s Folly, American agronomist Edward Faulkner posited that we’d be better off working the land in a way that mimics nature.

Faulkner’s wisdom languished in obscurity for decades, but soil depletion has slowly forced cultivators to embrace the idea. “No-till” tractor attachments emerged in the 1980s and ’90s. These cut a slit through crop residue without disturbing the soil, leaving a carbon-rich mulch atop fertile dirt.

Parking the plow isn’t a blanket solution, though. Small-seeded vegetables like lettuce struggle to take root, while large-​seeded commodities like corn and soy (the two most planted crops in the US) readily adapt. A farm’s yields might dip in the first few years after tilling stops, but adopters who master the art find they produce just as much—with significant savings on labor and fuel. Devotees tout the return of carbon to the ground as a panacea: Healthier soil begets healthier crops that require less fertilizer.

Cover crops further bolster the carbon-​farming lifestyle. Sown to enrich the soil rather than for harvest, plants like clovers, vetch, and various inedible radishes and ryegrasses are among the most common. Started after harvest in fall, before planting in spring, or as groundcover during the main growing season, they pull in carbon and add nutrients to the earth after they die. The cost adds overhead to a stead’s delicate fiscal existence, but according to a USDA survey of farmers, improved yields and reduced fertilizer spending help the practice pay for itself in an average of three years.

Those who combine no-till and cover crops capture about a half-ton of carbon per acre annually, according to analysis from Project Drawdown, an international collaboration of academics and advocates that assesses the potential impact of mitigation strategies.

Hardcore carbon farmers reach even further into the past and integrate trees—like Lanier and his silvopasture. The approach sponges up nearly 2 tons of atmospheric CO2 per acre per year. Other forms of mixing crops with woods (termed “agroforestry”) grab even more, making it the most potentially impactful shift, according to Drawdown’s data. The method can also be lucrative. Shade-grown chocolate fetches a premium for Brazilian farmers, and the hogs that become Spain’s famed jamón Ibérico fatten on oak-dropped acorns. Yet adoption faces a huge hurdle: It can take decades to recoup the cost of planting and nurturing a canopy.

At Cherry Farm, lead USDA researcher Alan Franzluebbers has begun to chew on the early data from his team’s gas sampling. As expected, the systems with the least soil disturbance and the most plant life hold more carbon. But smaller insights could lead to new tweaks. For instance, pine and walnut trees are better sinks than cypress and ash (good news for Lanier). Ultimately, Franzluebbers will convert those findings into climate-​conscious recommendations for the sandy plains of eastern North Carolina; similar experiments are running parallel in other regions. “We have to return carbon to the soil,” he says. “We need to move much quicker than we are.” Intrepid farmers aren’t waiting around.

Sowing plants like ryegrasses and radishes between cash crops helps the ground hold onto more carbon.

Sowing plants like ryegrasses and radishes between cash crops helps the ground hold onto more carbon. (Patrick Leger/)

On a clear, cold day in early March 2019, Justin Jordan, a fifth-generation grower in Lacona, Iowa, pores over old maps spread across his dining-room table. One creased, yellowing chart shows a soil-conservation plan his grandfather created with the USDA in the 1950s, including terraces for controlling erosion and areas designated for tree planting. The agency was working to reverse critical topsoil loss from decades of mass-scale plowing.

His grandfather implemented portions of the scheme. But new synthetic fertilizers, which could boost yields by 50 percent, made the situation less dire, so he continued tilling their corn and soybean fields each year. As did Jordan’s dad, and most other farmers. Over the past 150 years, cultivation has chewed up about half of Earth’s topsoil.

Jordan, an impeccably polite, soft-​spoken man in his late 30s, stopped plowing and began planting cover crops when he took over in the early 2000s. “I was eager to do things in a different way,” he says. “It just seemed like every year the topsoil was getting thinner.” Jordan tends 410 acres—larger than most farms hawking vegetables at Saturday markets, but tiny compared with 10,000-acre corporate operations.

Aerial photos show the contrast between his land and that of other farmers, most of whom continue heavy tilling. His soil is dark and rich, but from the air, his fields appear lighter, covered in accumulated mulch. Strips of perennial hay grass (for his cattle) and native prairie species like milkweed meander across the slopes—​year-round flora that pump carbon into the soil. Neighboring barren fields steadily release it.

Once Jordan brings in his corn in October, he sows a cover of rye among the drying stalks that stays green through the following spring, when he cuts it down and seeds next year’s crop in the mulch. He sprinkles his soybean fields before the September harvest with a cocktail of rye, radishes, and oats, creating a mini forest beneath the knee-high cash crop. With all these changes, his yields have remained roughly the same as his neighbors’.

Soon, folks like Jordan might gain a financial edge. The Terraton Initiative, the nation’s first carbon market dedicated to agriculture, launched in June 2019 out of the farm-tech startup Indigo Ag. Companies that want to offset their emissions purchase credits; Terraton then pays growers $15 per ton for the carbon their land captures. Within six months, farmers tending a total of 10 million acres worldwide—encompassing plenty of the massive steads that are the face of modern agriculture—expressed interest in signing up.

More cash would be nice, but climate change is the motivating factor for Jordan—out of global concern, and to keep his harvest from washing away. “When I was a kid, getting 2 or 3 inches of rain in one storm hardly ever happened,” he says. “Now we’re regularly seeing 6 or 7.”

Increased carbon leads to erosion-​resistant clumps called aggregates, plus a layer of plant residue that softens downpours. “I can take those big rains,” Jordan says, “and in a dry spell, having that blanket on the soil keeps me from losing moisture.” For every percentage-point increase in organic matter (the carbon-​rich product of decomposition), an acre of topsoil can hold an additional 20,000 gallons of water, according to USDA data.

As Jordan gives me a Jeep tour of his farm, passing a frozen pond and waist-high swaths of buff-​colored prairie grasses, he ponders his options for grabbing more carbon. He’d like to find a way to add trees, but it’s a long-term investment with little short-term upside. Crop prices have plummeted in recent years, so owners have scant appetite for risk, he says. “I’m in survival mode.”

Still, he’s proud to be part of a growing minority pushing carbon-farming practices as a weapon in the climate fight. In early 2019, he attended a Faith, Farmers, and Climate Action meeting at a church in Des Moines. The organizers—​a nonprofit that promotes a religious response to global warming—​have had early success in rallying a handful of growers in conservative Iowa communities to stop tilling and to plant cover crops.

However they’re recruited, carbon farmers need to become an army. Growers like Jordan represent the bulk of American agriculture (the average stead measures 443 acres), so the practice reaching its potential requires that both midsize outfits and larger-scale cultivators get on board. Taken together, Earth’s 12 billion acres of farmland could absorb all the CO2 that has built up in the atmosphere. Currently, the average concentration of carbon in soil is about 1 percent; bumping it to 3—ideal growing conditions—​on 30 percent of fields would get us there.

Jordan doesn’t care what incentive it takes—​cash, a desire like Lanier’s to be a “good steward” of the land, or the satisfaction of rebuilding topsoil—​to reach the unconverted. Realizing that our collective fate might hinge on this revolution, he’s frustrated with the pace of adoption. “Most farmers will do it only if they see a financial gain.” But, if nothing else, he’s gained something priceless: “I feel like I’m farming with a clear conscience.”

This story appears in the Spring 2020, Origins issue of Popular Science.

Source link

To Return to News Page – click here

Share this

0 Comments

Leave a reply

Your email address will not be published. Required fields are marked *

*