Perennial Crops Boost Biodiversity Both On and Off Farms. Researchers Explain How. | Civil Eats

Perennial Crops Boost Biodiversity Both On and Off Farms. Researchers Explain How.

Above and belowground, perennial crops including wheat, grasses, trees, and more provide habitat and nutrition to creatures that help make ecosystems whole.

Mallard eggs sit in a nest in a Kernza field. (Photo courtesy of courtesy of the University of Manitoba)

Mallard eggs sit in a nest in a Kernza field. (Photo courtesy of courtesy of the University of Manitoba)

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We have long reported on the many climate and food security benefits of perennial crops, whose roots stay in the soil year-round. But research also shows that perennial agriculture, which includes orchards, agroforestry, silvopasture, and row crops, also helps increase biodiversity—both on the farm and off.

“From an observational standpoint, having more perennials in a system makes sense,” said Ebony Murrell, a lead scientist at The Land Institute, a Kansas-based nonprofit that conducts research to help develop diverse, perennial, and regenerative agricultural systems at scale. “We’re trying to better mimic ecological processes to produce a system that can better provide ecosystem services.”

On farms, perennial crops provide year-round homes for a number of species, from insects to mammals to soil microbes. For instance, a 2022 study that Murrell helped conduct found that flowering perennial border crops support particularly robust pollinator communities. That’s in part because most bees native to the U.S.—like sweat bees and long-horn bees—are solitary and live underground, and they require undisturbed habitat.

A flowering grain legume called sanfoin is good at attracting honeybees and native leafcutting bees, Murrell said, and a sunflower-like native prairie plant called silflower, which is being developed as an oilseed crop, is popular among native bees. “We have so far found over 35 species of bees visiting that one plant,” Murrell said. “We are interested in trying to get it planted in more places to help serve that purpose.”

Additionally, perennial crops like Kernza, the grain developed by The Land Institute, provide habitat for ground-nesting birds and other animals. “A vegetated landscape is going to accommodate species that a tilled, denuded landscape as far as the eye can see does not,” said Tim Crews, chief scientist at The Land Institute and director of its international program. “There are going to be a lot of species that take advantage of it.”

A mallard takes flight from its nest in a Kernza field. (Photo courtesy of courtesy of the University of Manitoba)

A mallard takes flight from its nest in a Kernza field. (Photo courtesy of courtesy of the University of Manitoba)

Perennials’ long-lived and deeper root systems build more biodiversity underground as well. A study published in January 2020 found the fungal microbiome in the soil of a single stand of Kernza closely overlapped with the soil microbiome of native restored prairie—and was quite distinct from the microbiome of a field planted in a tilled rotation of three annual crops—suggesting that Kernza cropping systems “have the potential to mimic reconstructed natural systems.”

While the microbial community overlap was high across the board, it was particularly high for mutualists, or beneficial fungi that consume organic matter and release nitrogen for the plants, as well as saprophites, or decomposers.

“If you add carbon to soils, you almost always get a pretty big response in terms of the microbial community growing to consume that carbon,” said Crews, one of the study’s authors. “And there’s zero question that the amount of available carbon that gets added to the topsoil of an agricultural field is far greater—many-fold greater—in Kernza compared to annual wheat or any of the annual grains. I mean, there’s so much more root system, and those roots turn over, they die back some every year, and there’s a huge amount of carbon that goes into the soil.” And, he added, higher-functioning beneficial mycorrhizal fungi tend to develop in the undisturbed soil of perennials.

Researchers point out that perennial crops also benefit off-farm biodiversity, because they reduce the negative impacts of traditional agriculture on the environment. “The Mississippi Basin’s annual dead zone in the Gulf of Mexico is from nitrogen leaching out when there are no roots in the soil and there’s no activity,” said Crews. With perennial covers like Kernza, he continues, “the vast, vast majority of nitrate leaching stops.”

Additionally, he said, “There’s increasing evidence that you lose less in nitrous oxide fluxes as a greenhouse gas, because these crops take up the nitrogen so quickly, and year-round—you don’t have times of the year when there are no plants to take up nitrogen.”

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Prairie chicks wait for food in their nest in a Kernza field. (Photo credit: Patrick LeHeiget, University of Manitoba)

Prairie chicks wait for food in their nest in a Kernza field. (Photo credit: Patrick LeHeiget, University of Manitoba)

To make the most of perennials’ ability to produce both on- and off-farm biodiversity, some researchers and farmers are following the example of Indigenous people, who have thoughtfully stewarded landscapes for millennia.

While farmers often rotate their annual crops or plant cover crops during the off season, “the idea with perennial crops is that you want them to stay in the ground for many years, which means you’re not rotating anymore. So how do you take that diversity in time and move it to diversity in space?” Murrell asked. The answer: strategically planting different perennials together to benefit one another.

A few examples: planting silflower with a perennial groundcover like turf grass, which provides a natural weed barrier. Alternating rows of Kernza with rows of alfalfa to provide Kernza with nitrogen and prevent the grain from clumping together, competing with itself, and becoming less productive, which it tends to do after a few years when planted alone. Growing two flowering species that bloom at slightly different times together to support pollinators. Or practicing agroforestry by incorporating trees or shrubs into farming systems, while producing additional forest products like fruit, nuts, or mushrooms.

“The real powerhouse of our agriculture is based on grain crops and grazing crops, but trees are an amazing addition to the toolkit,” said Fred Iutzi, director of research and commercialization with the Savanna Institute. Because they’re perennial and tall in stature, they help create an important year-round diversity of ecosystems in the farm landscape, in addition to supporting a diversity of species, Iutzi said.

“The real powerhouse of our agriculture is based on grain crops and grazing crops, but trees are an amazing addition to the toolkit.”

Several efforts to promote perennial agriculture have received influxes of funding in recent years. As part of last year’s Partnerships for Climate-Smart Commodities funding program within the U.S. Department of Agriculture (USDA), the agency dedicated $60 million to agroforestry, for instance.

The Savanna Institute plans to scale up its agroforestry work as a result, said Iutzi. “And that will work hand in glove with the money that’s available for farmer incentives, as farmers will receive free technical assistance here and in making agroforestry a reality on their farms.”

The Savanna Institute also plans to use some of the new funding to measure and document indicators like how agroforestry practices mitigate greenhouse gas emissions, and to develop relationships with processors and buyers that might be interested in expanding their Midwest sourcing of perennials like tree fruit and nut crops.

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In 2020, the USDA also awarded $10 million to a coalition of farmers, scientists, educators, policymakers, and food industry players to help scale up Kernza production. The five-year Kernza CAP initiative, spearheaded by The Land Institute and the University of Minnesota, recently released its year-two annual report outlining its progress on efforts like creating recommendations for optimizing yield, profitability, and environmental quality and developing supply chains and products.

Iutzi believes that perennials can help solve many of the problems facing the world—and that we need to think of agricultural productivity in a more holistic way that includes factors like biodiversity. “One of the biggest challenges in front of humanity is how we get both ample food while providing a stable climate, healthy soil, clean water, and biodiversity,” he said. “We have to expect both from our agricultural landscapes.”

Christina Cooke is Civil Eats' associate editor. Based in North Carolina, she has also covered people, place, science, business, and culture for venues including The New Yorker, The New York Times, TheAtlantic.com, The Guardian, Oxford American, and High Country News. In the past, she has worked as a staff writer for the Chattanooga Times Free Press in Tennessee and a weekly paper in Portland, Oregon. A graduate of the documentary writing program at the Salt Institute of Documentary Studies and the creative nonfiction writing MFA program at Portland State University, she teaches interviewing and nonfiction writing at the Center for Documentary Studies at Duke University. Find out more at www.christinacooke.com. Read more >

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