The hidden beauty of the plants that feed the world
Seen through a microscope, a cornucopia of common crops offer lessons on new techniques for making agriculture more sustainable.
Pizza lovers no doubt will appreciate the flower bud of the arbequina olive tree, seen here at 80-times magnification, which grows the luscious black olives popular at restaurants. Olive trees are a perennial, woody plant capable of long-term carbon sequestration. The International Olive Council says they olive absorb 11 kilograms of CO2 per liter of olive oil produced. In many parts of the world, olives are a staple food, but climate chaos can wreak havoc on groves. Italy grows over 500 varieties, and its olive oil industry was worth more than three billion euros in 2017. Then, in 2018, the industry crashed. Freak cold, heat, and rain events weakened trees, which were harmed further by the spread of an invasive tropical bacteria. Thousands of trees, some as old as 1,400 years, were removed in an attempt to block the spread of this scourge. In Morocco, some growers are planting olive trees on hillside terraces to reduce erosion and using drip irrigation to bring water to the trees. Spanish missionaries planted olive trees in California during the 18th century, and they’ve thrived, producing mostly table olives. Warming temperatures, unpredictable weather, and increasing wildfires are also prompting growers to plant dozens of olive cultivars to the north, in Oregon. Boutique olive oil producers there hint at a possible northward shift of food production in North America.
Scanning Electron Microscope photograph by Robert Dash
Story and micrographs byRobert Dash
September 23, 2021
•7 min read
From the salad course to dessert, most of the foods on your plate can be traced back to carefully cultivated plants. Even the meat you eat likely comes from animals fed parts of crops, passing energy harvested from the sun up the global food chain.
But modern agriculture exacts a huge environmental cost. Crops such as corn and soy are often grown in large monoculture farms that are maintained with fertilizers and pesticides made using fossil fuels. Slash-and-burn practices can decimate carbon-capturing forests and pump excess carbon dioxide into the air. Heavily tilled soils destroy fungal networks that otherwise bind the dirt, wasting already drought-stressed water supplies and contributing to erosion. These are just a few of the ways that our food systems are tied to climate change. Recent estimates peg agriculture's total share of greenhouse gas emissions at over 30 percent.
To help mitigate this problem, on September 23, the UN Food Systems Summit will highlight sustainable solutions for agriculture during the virtual event. The goal: “Everyone, everywhere must take action and work together to transform the way the world produces, consumes, and thinks about food.”
As part of a move toward more sustainable farming, an increasing number of food producers and investors are embracing advanced methods, as well as some used in the distant past, loosely described as regenerative agriculture. These practices—such as boosting plants' genetic diversity and planting "cover crops" that fix nitrogen from the atmosphere and add it to the soil—can help improve soil health and return more carbon to the earth.
SUNFLOWERSpiked pollen covers a sunflower floret seen here at 700-times magnification.
Researchers interested in exploring the virtues of the sunflower recently formed a worldwide team to examine the plant’s genetic library. They found that the sunflower genome is 20 percent larger than the human genome, with about twice the number of genes. This allows for a great diversity of genetic combinations, which have given rise to 70 species of sunflowers.
Having a genome map is a key step in understanding how these remarkable plants thrive in stressful environments. Highly resistant to drought, increased heat, high salinity, and disease, sunflowers are second only to corn as a worldwide hybrid seed crop. Seed collectors are preserving wild varieties as a hedge against future climate stress.
Farmers plant sunflowers as part of a mix of cover crops to improve soil, conserve water, and reduce pesticide use. At the Land Institute in Salina, Kansas, scientists are attempting to breed perennial varieties that require less tillage, fertilizers, and pesticides.
Scanning Electron Microscope photograph by Robert Dash
FAVA BEANA few pollen grains cling to the anther of a fava bean flower in an image taken at 3,400-times magnification.
Fava beans are an important cover crop, which reduces the need to use synthetic fertilizers. The work of fixing nitrogen is done by bacteria that live on root nodules, seen in this image.
Researchers in Denmark promote fava beans as a local source of plant protein that is easily digested. Scandinavian countries with cooler climates benefit from this crop, substituting it for soy imported from distant countries. Some pet food manufacturers add fava-bean protein to their products, helping reduce demand for ocean-caught fish.
Fava beans can cause favism, a severe anemic reaction in people with an inherited G6PD enzyme deficiency. To address this, scientists have worked to eliminate compounds in the beans that trigger the ailment.
Scanning Electron Microscope photograph by Robert Dash
TomatoThis seed, seen at 34-times magnification, comes from the Solanum sitiens tomato plant, the wild relative of modern tomatoes, which grows in Chile’s Atacama Desert.
Every contemporary food crop originated hundreds—even thousands—of years ago from what scientists call a crop wild relative. In our era of rapid climate change, these wild varieties have newfound importance as a hedge against frailties in modern crops developed under more stable conditions that are less diverse genetically. Researchers are collecting and saving crop wild relative seeds and evaluating their genes as counters to stressors such as drought and salinity.
Growers are experimenting with new tomato varieties that can do well despite the challenges of flooding and drought, growing season shifts, pests, and losses of pollinators such as bees. In Kenya, for example, farmers are responding to climate threats by adjusting their planting and harvesting times, planting new varieties, and transporting picked produce during cooler times of day.
In the United States, tomato expert Brad Gates has been introducing new varieties since the mid-1990s. Better breeding and more diversity, he says, will ensure the tomato’s survival and future success.
Scanning Electron Microscope Photograph by Robert Dash
CARROTThe delicate branches of a humble carrot leaf create a stately form when seen at 300-times magnification.
Wild swings of drought and flooding affect carrots, as with so many vegetable crops. Carrot seeds need steady moisture and are damaged by intermittent drying. Excessive heat causes the plants to grow leaves faster and flower prematurely, making the carrots bitter and woody. In California, carrots have suffered from drying soils after years of drought, and experiments are being done with the goal of developing carrots better able to withstand such conditions.
Australian researchers have confirmed that carrots grown in hot temperatures are inferior in flavor and texture, suggesting that carrots’ optimal range for growth will shift south to cooler, wetter Tasmania.
As temperatures and CO2 levels rise, carrots likely will lose nutritional value. The Crop Wild Relatives Project is cross-breeding today’s carrots and other crops with their wild relatives to increase resiliency to drought, heat, and increased salinity. Drawing on wild plants to introduce more diverse genetic material will help keep our essential food plants robust and nutritious in a challenging future.
Scanning Electron Microscope photograph by Robert Dash
KALESeen at 240-times magnification, the anther of a kale flower covered with pollen seems to beckon hungry observers.
In the U.S., annual sales of organic foods have topped $50 billion and continue to climb. This represents roughly 6 percent of total food sales. A surge in demand for once humble kale is emblematic of the shift. Marketers named kale a superfood, elevating its status as a must-have for the health-conscious. But when it comes to greenhouse gases resulting from organic farming practices, the picture is not always so rosy. Evidence is mounting that large-scale organic farms may release more greenhouse gases than conventional farms.
Many organic farms rely on diesel-burning machinery to suppress weeds and pests. Crops grown on large organic farms also can be heavily dependent on tillage. This deep rupturing of soil destroys microbial and mycelial networks necessary for soil health and carbon capture. Manure used by many organic farms increases methane, a greenhouse gas.
Industrial farming excels at raising crop yields by using heavy machinery, chemical fertilizers, fungicides, pesticides, irrigation, and automated harvesting. What has been lost is the expertise to coax the biological and ecological health of soil and its carbon-capture potential. If grown under ideal conditions, kale will truly be a superfood.
Scanning Electron Microscope photograph by Robert Dash
RICEPollen coats two anthers from a rice flower, seen here at 340-times magnification.
More than a billion people depend on rice cultivation for their economic and cultural sustenance. The Anishinaabe and Menominee Nations in the U.S. Upper Midwest have sustainably harvested wild rice they call manoomin for several hundred years. This food is so central to their culture that the Menominee take their name from it.
The importance of rice makes any threats to yields—such as reduced nutrient content and salt damage—a humanitarian concern. Technological innovations used to fortify rice promises more nutrition. Genetically modified “golden rice” has been approved for production in Bangladesh and the Philippines, where its elevated vitamin A content may help save children’s lives. But GMO opponents tout sweet potatoes, carrots, and the fruits of the moringa tree as plants with the right stuff to address vitamin A deficiencies.
The significance of rice crops goes beyond nutrition. Rice plants draw silica from the soil and pack it into husks to protect seeds from pests. Waste husks with their silica can be reclaimed for industrial uses, from tires and silicon wafers to toothpaste and batteries. Husks can also be used to produce biochar, which helps store carbon in the soil.
By some estimates, though, rice fields contribute up to 17 percent of global methane emissions because the bacteria that thrive among their roots emit the gas. New farming methods that eliminate those bacteria are being developed.
Scanning Electron Microscope photograph by Robert Dash
CHIAChia seeds, like the fragment seen here at 800-times magnification, are a pseudo-cereal containing minerals, antioxidants, fiber, fatty acids, and all nine essential amino acids. They were staple foods for the Maya starting more than 3,000 years ago. Chia today is touted as a gluten-free superfood with climate-smart applications, and it provides an inexpensive source of essential nutrition for poor communities.
Booming demand has spurred interest in chia in agricultural regions, especially in Uganda and East Africa. There, smallholder and refugee farmers may earn up to five times more from chia than from their traditional cotton crop.
Chia seeds have a gelatinous coating that helps retain water. Researchers are analyzing this with the goal of adapting it for other drought-threatened species. Chia is also being promoted in Egypt and the Middle East as a valuable crop that needs much less water than traditionally grown wheat.
Scanning Electron Microscope photograph by Robert Dash
HOP LEAFSeen at 240-times magnification, the surface of a hop leaf is covered in hair-like protrusions called trichomes.
Hops and barley are crucial for brewing beer, but some hop varieties used for popular craft beers are under threat from drought, high temperatures, and extreme weather. Washington State’s Yakima Valley is one of the world’s largest hop growing regions, but reduced snowpack and shrinkage of glaciers in the Cascade Mountains means less water for hop farms.
Hops are susceptible to pests and molds, challenges exacerbated by unpredictable weather. Producing hops indoors is one solution. Meanwhile, researchers are making beer with a gene-edited fermented yeast juiced with mint and basil instead of hops. Remote regions in the U.S. Southwest offer hardy, wild hop varieties that might yield a tasty climate-friendly beer, and some states, such as Florida, are having new success growing hops in winter.
Scanning Electron Microscope photograph by Robert Dash
LION'S MANE MUSHROOMA lion’s mane mushroom tendril reveals its complexity seen at 400-times magnification.
It’s hard to overstate the importance of fungal networks for creating healthy soil, optimum conditions for plant growth—and, remarkably, rain. Acting like an internet of the soil, its interwoven threads, known as the fungal mycelium, transport micronutrients to plants through their branching filaments. In exchange, this fungal “mat” is fed sugars produced by plants during photosynthesis. The mat binds soil and helps break down dead plants and animals, and it releases trillions of fungal spores into the air that act as rain “seeds,” helping to create clouds.
In northern forests, where 16 percent of planetary carbon is stored, mushrooms are better than trees at capturing carbon. Beyond that, several species of mushrooms have proven effective at combating cancer and other diseases, and extracts from them can be used to bolster honeybees’ immunity to viral infections that can cause colonies of these crucial pollinators to collapse.
Fungal networks have industrial applications too. Mycelial threads blended with waste corn stalks and wood fiber create composites for packing materials, plastics, and adhesives. These products behave like cork, rubber, plastic, and leather. And when discarded, they add nutrients to the soil.
Scanning Electron Microscope photograph by Robert Dash
BLUEBERRYA tiny blueberry seed seems coated with scales when seen at 300-times magnification.
Seasonal shifts that bring new pests, extreme weather, and fewer pollinators are affecting blueberries worldwide. Random freezes on top of early budding can wipe out crops. In the 1850s, Henry David Thoreau documented May 16 as the average flowering time for high-bush blueberries near his home at Walden Pond, in Massachusetts. In 2012, Boston University biologist Richard Primack found the average today to be April 23, with the earliest date being April 1.
As with so many crops in the Northern Hemisphere, the range in which blueberries thrive is moving to higher latitudes, and Quebec now competes with Maine as a source of wild blueberries. Additional threats come from the invasive spotted-wing drosophila, a type of fruit fly that harms young berries and thrives in warming weather.
Savvy consumers pay careful attention to the geographical origins of their food. But many locavores might be surprised to learn that it’s the method of transportation, more than the distance traveled, that may have greater impact on a food’s carbon footprint. Once blueberries are harvested, for example, the carbon footprints of their transportation methods differ greatly. "Climate-Smart Food" author David Reay found that a box of blueberries grown locally in the U.K., or one transported there by ship from other countries, have a similar carbon footprint—about one-tenth that of a box sent by air. It’s a good argument for “pick-your-own” farms.
Scanning Electron Microscope photograph by Robert Dash
A version of this story appears in the February 2022 issue of National Geographic magazine.
