Return of the Perennials | A Visual Essay

Modern annual grain crops are feeding the world. But their short rooted, short-lived nature may be robbing our soils of a productive future.

Over 70% of global cropland is dedicated to agricultural grains, with 42% of the world’s food calories coming from just three staple grains — rice, wheat and maize.^1,2 This narrow focus allowed larger producers to scale up, mechanise, and optimise their farming operations to meet the growing needs of a growing global population. But decades of producing just a handful of single season or ‘annual’ grains at this scale has come at a cost to the land.

Today, an estimated 24 billion tonnes of fertile soil is being lost each year as farmers continue to intensively disrupt soil and persist with the heavy use of fertilisers and pesticides to maintain yields in increasingly barren soils — a rate that far outpaces the natural replenishment of new productive topsoil.³ In recent years, this has led to widespread concern about the long term impacts for global food security. But there may be a natural low-tech solution to help reverse this pattern. And it's been right in front of us for a very long time. 

The power of perennial grains

Unlike modern annual crop varieties, which have a one-year life cycle and are harvested each year, perennial crops live for two or more years and remain in the ground over multiple years as their roots slowly grow deep into the soil. With deep root systems that can scavenge nutrients and water when they are scarce, perennials are able to maintain coverage above the ground through the seasons, binding the soil and reducing erosion. And with increasingly uncertain seasons in many growing regions, the humble perennial may be one of our food system’s safest hedges against the impacts of a changing climate. Still, despite the many positives, perennial grain varieties are not widely cultivated. So why is this? And could they really offer a solution to future global food security? To understand, we need to take a closer look at what makes perennials so different.

 

“Frequently, half — and often much more — of every crop plant is invisible. This portion consists entirely or largely of roots which extend far into the soil” - John E. Weaver

American botanist, prairie ecologist and Professor at the University of Nebraska, John E. Weaver, began to research these distinctions in his 1926 book Root Development of Field Crops.⁴ With the help of a team of assistants, Weaver studied and meticulously illustrated the roots of both annual crops and native prairie perennials, digging deep trenches to view the plant’s root systems from the side. They not only investigated the structure, but also the effect of the environment, soil types and structure on the plants. And the findings were clear.

The Root Development of Field Crops, John E. Weaver, 1926

Looking at Weaver’s drawings, we see that different species of plants have different types of root system; some are shallow, extending more horizontally a small distance around the plant, while some go far deeper into the depths of the soil. We now know that it's these long rooted plants that could be key in building a more resilient food system to handle climate change. To understand why roots are so crucial, we need only to take a look back to the history of the Great Plains—America’s breadbasket—where Weaver was working.
 

Historically, nearly one-third of the US consisted of open prairie grassland; forming the continent’s largest ecosystem.⁵ Before the arrival of Europeans, Indigenous peoples hunted the vast herds of bison that roamed the prairies (naturally fertilising the soil as they went), and supplemented their diet with wild perennial grains and seeds from the native prairie grasses, such as Indian Ricegrass.⁶ The naturally deep root systems and continuous cover of these perennial grasses helped to prevent soil erosion and protect the balance of the prairie ecosystem from the extreme weather fluctuations of the prairie landscape.⁵
 

“The roots of plants are efficient soil binders, the effect being more continuous with perennials… Not only do the underground stems and roots hold the soil, but the tops form a complete surface cover which efficiently shields the soil from the destructive action of wind and water. Removal of the cover of vegetation, whether by overgrazing or plowing, results in root decay and is frequently followed by soil erosion.”

John E. Weaver, The Root Development of Field Crops, 1926

False boneset has one of the deepest root systems of any native plant in mixed grass prairie, penetrating more than 17 feet down into the soil. During severe droughts, when all other plants have gone dormant or died for lack of moisture, false boneset remains green. Photo: Tom Koerner/USFWS

Following the arrival of the first Europeans to the prairies in the early 1800s, many attempted to cultivate the landscape using simple tools, but it would come with little success.⁷ With only basic hand tools, it was incredibly difficult to dig into the dense root systems created by native perennial grasslands. But the innovation of the cast-steel plough in 1837 by blacksmith John Deere quickly changed that. The steel plough allowed farmers to rip into the soil and cut through the deep roots, before planting a number of more familiar and manageable crops such as annual wheat. Unbeknownst to farmers at the time, that first turning of prairie soil would mark the beginning of unimaginable hardships in the prairies.
 

Biologist Janine Benyus in her book ‘Biomimicry: Innovation Inspired by Nature’ tells the tale of a Lakota person, who while watching the landscape being ploughed, turned to the farmer and said “wrong side up”, referring to the upturned roots now laying above ground. Benyus continues, explaining how “mistaking wisdom for backwardness, the settlers laughed as they retold the story, ignoring the warning shots that fired with each popping root”.⁸ Replacing perennial prairie grass with annual wheat was unknowingly destroying the landscape. And as perennial plants were ripped from the ground, local ecosystems quickly fell apart. Soils degraded from tightly bound nutrient rich land into loose dry dust fields, capable of burying entire towns when whipped up by strong local winds
 

Top: Plowing the prairie. Cascade County, Montana, 1939; Left: Turning the Prairie, 1860-1920; Right: A virgin prairie, improved by Mr. and Mrs. Flickinger, 1884-1914. (The New York Public Library Digital Collections)

In 1863, President Abraham Lincoln encouraged further ploughing of the prairie with the Homestead Act, promising 160 acres of free land to anyone who could claim and cultivate it for five years. This was followed by the Enlarged Homestead Act in 1909, which doubled this to 320 acres per settler. In 1917, 45 million acres of wheat was cultivated and harvested; two years later it was 75 million acres.⁸

In the 1930s, the freshly toiled prairie landscape would face its first test of resilience when a severe drought caused one of the most infamous agricultural crises in US history. The ‘Dust Bowl crisis’ devastated the southern plains with powerful dust storms that choked the region from Texas to Nebraska, leading to crop failure, widespread famine, disease and ultimately the death of both livestock and residents in the area. Without the deep roots of the grasses and permanent cover of perennial plants, over 20 tonnes of topsoil per acre were lost annually in the Midwest during this period of almost a decade due to wind erosion.⁹

South of Lamar, Colorado, a large dust cloud appears behind a truck traveling on highway 59, May 1936. (Photo by PhotoQuest/Getty Images)

And yet, the widespread monoculture farming of annual wheat continues to this day throughout the prairies. The US is currently the world’s 4^th largest wheat producer, harvesting 1.81 billion bushels of wheat on 49.58 million acres of planted area in 2023 — more than double the production of 1930, right before the Dust Bowl crisis.^{10, 11, 12} Thanks to advancements in farming technologies and practices, this production level has remained static for the past few decades, with annual yields averaging around 42 bushels per acre since the late 1990s.¹³ The cumulative cost of this approach on US soil management has been significant. Over the past 160 years, around 57 billion tonnes of topsoil has been lost in the US alone — largely attributed to agricultural tillage. This historical rate of loss is nearly double the rate which the USDA considers sustainable for soil health.¹⁴

Now, heavily reliant on synthetic inputs to provide a yield from otherwise lifeless soil, farmers in the region face the added pressures of climate change and increasingly unpredictable weather patterns, further eroding soils and presenting new challenges.
 

Rebuilding soils (the old way)

In recent decades, 40% of US cropland in the Midwest area has been converted to no-till practices, which has slowed the rate of erosion. Still, it’s estimated that the area loses soil and soil organic carbon significantly faster than the rate at which new topsoil is created.¹⁵ Conversion to 100% no-till agriculture in these midwestern U.S. states could help reduce this level of erosion by as much as 95%, but it would require an enormous shift in current production.¹⁶ 

This is where perennials come in. While no-till annual grain systems remain reliant on herbicides and fertilisers, perennial grains offer a viable input-free option to compete against annual weeds while producing food. The concept of growing perennial crops isn’t an unfamiliar one either. Even in modern agriculture, many of our tree grown crops like apples, olives and citrus remain in the ground over multiple seasons. These longer root networks provide much greater resilience to environmental stresses when times are tough, and are able to sequester carbon more efficiently than annuals. The year round cover above ground also helps to support biodiversity, creating diverse multi-season ecosystems while also producing food for human consumption.^{16, 17}
 

Why more farmers aren’t switching to perennials

Unfortunately, perennial alternatives to our commonly produced annual crops are still a long way from yielding volumes capable of meeting the current demand on grains. History has also shown us that developing perennial grains that can stand up to annual crop yields is not an easy task. In the 1930s, Soviet researchers tried to breed perennial wheat using hybridization techniques, but their efforts were not successful, and the idea was dropped a few decades later. Around the same time, scientists in California were able to develop lines of perennial wheat varieties that produced yields comparable to those of low-yielding varieties that were already in use. However, as modern annual wheat yields have continued to increase, these low-yielding perennial wheat types have diminishing economical viability.¹⁸

With advancements in genetic technology, recent decades have seen a resurgence in the research of perennial grains, and development of varieties with commercial viability. In the past few years there have been some promising developments, including perennial rice cultivars with yields comparable to annual rice, and perennial sorghum developed through hybridisation with annual sorghum to produce high yielding varieties.¹⁷ In several countries around the world there are programs now dedicated to the development of hybrids or perennial varieties of wheat, rice, sorghum, oats and barley.¹⁶

Transitioning farmers will need support

This research and the desire to transition farms to perennial systems is a good thing, but it must also be backed by policy and government funding if it’s going to work. Perennials are often slower to grow, meaning a slower return on investment for farmers. Combined with a lower predictability of results when it comes to perennials, farmers will need incentives to justify the added financial risk of a transition to this way of growing. In the US, farmers growing annuals are currently protected by federal crop insurance from the USDA — if they move away from these crops, it leaves them responsible for bearing a huge financial risk. In a 2010 article in Science, scientists from 19 universities across five continents demanded significant investment in perennial grain crops, urging the necessity for innovative solutions to the combined impact of climate change, population growth and resource depletion on global food security.
 

Thankfully, governments are beginning to respond to this call: in 2020 the USDA provided $10 million to non-profit organisation the Land Institute — one of the forerunners for research and development into perennial crops in agriculture. 

Comparison of annual (left) and perennial (right) wheat across 4 seasons.

With roots up to 10 feet (3 meters) long, Kernza (on the right for each season, compared with annual wheat) yields abundant carbon storage as well as edible grain. Image courtesy of The Land Institute

Sold under the trade name Kernza in the US, the Land Institute’s domesticated variety of wild perennial grain is the first of their developments to be commercially available for transitioning farmers. Identified as a promising candidate for domestication, Kernza is considered the closest perennial relative to common wheat.¹⁶ The yields of Kernza are still only one third of modern annual wheat varieties, but the lower requirement for synthetic inputs and labour, as well as the ability to reduce nitrate leaching and make better use of soil moisture, make it a strong option for continued development.^{15, 20}
 

The Land Institute worked with photographer Jim Richardson to visualise the root systems of both annual wheat and perennial Kernza crops, excavating the ground to reveal what was below just as Weaver did nearly a century before.

While there’s still some way to go to develop Kernza into a true competitor to annual wheat, it’s not alone in the fight for sustainable crop production. Recent successes in perennial rice development have also shown yields equivalent to annual rice over eight harvests.²¹ And with 58% of farmers stating that they were “interested” or “very interested” in growing perennial grains (rising to 73% amongst farmers who were already aware of these crops) in a survey conducted by Cornell University in 2016, it’s clear that those who grow our food are also open to a new way of doing things.¹⁹

As momentum slowly shifts in favour of new ways to grow food, the will to integrate these new(old) is a good sign for our future. Ideally, that future looks like a system that can feed us while improving ecosystems and benefitting producer livelihoods — all at once. But this time, we’ll need to do things right. And that may just mean a few steps back before we step forwards.